SCIENCE LIBRARY

Abbott, J. D., et al. (2004). "Stromal cell-derived factor-1alpha plays a critical role in stem cell recruitment to the heart after myocardial infarction but is not sufficient to induce homing in the absence of injury." Circulation 110(21): 3300-3305.

BACKGROUND: After myocardial infarction (MI), bone marrow-derived cells (BMDCs) are found within the myocardium. The mechanisms determining BMDC recruitment to the heart remain unclear. We investigated the role of stromal cell-derived factor-1alpha (SDF-1) in this process. METHODS AND RESULTS: MI produced in mice by coronary ligation induced SDF-1 mRNA and protein expression in the infarct and border zone and decreased serum SDF-1 levels. By quantitative polymerase chain reaction, 48 hours after intravenous infusion of donor-lineage BMDCs, there were 80.5+/-15.6% more BDMCs in infarcted hearts compared with sham-operated controls (P<0.01). Administration of AMD3100, which specifically blocks binding of SDF-1 to its endogenous receptor CXCR4, diminished BMDC recruitment after MI by 64.2+/-5.5% (P<0.05), strongly suggesting a requirement for SDF-1 in BMDC recruitment to the infarcted heart. Forced expression of SDF-1 in the heart by adenoviral gene delivery 48 hours after MI doubled BMDC recruitment over MI alone (P<0.001) but did not enhance recruitment in the absence of MI, suggesting that SDF-1 can augment, but is not singularly sufficient for, BDMC recruitment to the heart. Gene expression analysis after MI revealed increased levels of several genes in addition to SDF-1, including those for vascular endothelial growth factor, matrix metalloproteinase-9, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1, which might act in concert with SDF-1 to recruit BMDCs to the injured heart. CONCLUSIONS: SDF-1/CXCR4 interactions play a crucial role in the recruitment of BMDCs to the heart after MI and can further increase homing in the presence, but not in the absence, of injury.

Abdallah, B. M. and M. Kassem (2008). "Human mesenchymal stem cells: from basic biology to clinical applications." Gene Ther 15(2): 109-116.

Mesenchymal stem cells (MSC) are a group of clonogenic cells present among the bone marrow stroma and capable of multilineage differentiation into mesoderm-type cells such as osteoblasts, adipocytes and chondrocytes. Due to their ease of isolation and their differentiation potential, MSC are being introduced into clinical medicine in variety of applications and through different ways of administration. Here, we discuss approaches for isolation, characterization and directing differentiation of human mesenchymal stem cells (hMSC). An update of the current clinical use of the cells is also provided.

Abkowitz, J. L., et al. (2003). "Mobilization of hematopoietic stem cells during homeostasis and after cytokine exposure." Blood 102(4): 1249-1253.

We created parabiotic mice, joining ROSA26 and PeP3b animals, to study the trafficking of hematopoietic stem cells (HSCs) from marrow to blood and their return to marrow. The transfer of HSCs was assayed by secondary marrow transplantation and was 1.0% to 2.5% after 3, 6, 8, and 12 weeks. Thus, HSC homeostasis is primarily maintained by the retention of stem cells derived from replication events within the marrow, not the homing and engraftment of HSCs from the circulation. Of interest, the phenotypes of marrow progenitors and granulocytes were similar to those for HSCs, implying that the marrow functions as an intact compartment where differentiating cells derive from endogenous HSC. In contrast, 50% of splenic granulocytes and progenitor cells derived from the parabiotic partner, suggesting splenic progenitor cells were in constant equilibrium with progenitors in blood. In additional studies, animals were exposed to granulocyte-colony-stimulating factor (G-CSF) and stem cell factor at days 17 to 20 of parabiosis and were studied 3 weeks later; 10.1% of marrow HSCs derived from the parabiotic partner. These data imply that HSCs, mobilized to the blood in response to cytokine exposure, are destined to later return to marrow, an observation that supports the concept that the mobilized peripheral blood stem cells used in clinical transplantation function physiologically.

Aggarwal, R., et al. (2012). "Hematopoietic stem cells: transcriptional regulation, ex vivo expansion and clinical application." Curr Mol Med 12(1): 34-49.

Maintenance of ex vivo hematopoietic stem cells (HSC) pool and its differentiated progeny is regulated by complex network of transcriptional factors, cell cycle proteins, extracellular matrix, and their microenvironment through an orchestrated fashion. Strides have been made to understand the mechanisms regulating in vivo quiescence and proliferation of HSCs to develop strategies for ex vivo expansion. Ex vivo expansion of HSCs is important to procure sufficient number of stem cells and as easily available source for HSC transplants for patients suffering from hematological disorders and malignancies. Our lab has established a nanofiber-based ex vivo expansion strategy for HSCs, while preserving their stem cell characteristics. Ex vivo expanded cells were also found biologically functional in various disease models. However, the therapeutic potential of expanded stem cells at clinical level still needs to be verified. This review outlines transcriptional factors that regulate development of HSCs and their commitment, genes that regulate cell cycle status, studies that attempt to develop an effective and efficient protocol for ex vivo expansion of HSCs and application of HSC in various non-malignant and malignant disorders. Overall the goal of the current review is to deliver an understanding of factors that are critical in resolving the challenges that limit the expansion of HSCs in vivo and ex vivo.

Al-Khaldi, A., et al. (2003). "Therapeutic angiogenesis using autologous bone marrow stromal cells: improved blood flow in a chronic limb ischemia model." Ann Thorac Surg 75(1): 204-209.

BACKGROUND: We evaluated the effect of autologous marrow stromal cells (MSCs) on neovascularization and blood flow in an animal model of chronic limb ischemia. METHODS: Chronic hind limb ischemia was created by ligating the left common iliac artery of male Lewis rats. Three weeks after ligation, 5.0 million LacZ+MSCs (n = 10) or culture medium (n = 10) were injected into the anteromedial muscle compartment of the left thigh. At 4 and 6 weeks after injection, half the animals (n = 5) from each group underwent femoral artery ultrasonic blood flow measurements of the ischemic and nonischemic limbs to obtain a flow ratio. The animals also underwent angiography and measurements of blood vessel density and arteriolar density. Qualitative histologic assessment of the limb muscles was performed. RESULTS: LacZ+MSCs were found to differentiate into endothelium (F VIII+), vascular smooth muscle (positive a-smooth muscle actin), skeletal muscle (positive desmin), and adipocytes. Ischemic hind limbs where MSCs were implanted had greater vascular density and arteriolar density than control limbs (p < 0.001). Femoral artery flow index (left femoral artery flow/right femoral artery flow) was 0.89 +/- 0.12 and 0.90 +/- 0.06 for rats injected with MSCs measured at 4- and 6-weeks, respectively, compared with 0.50 +/- 0.15 and 0.50 +/- 0.10 for the control rats (p < 0.001). Angiography demonstrated reconstitution of the left femoral artery in rats that received MSC implantation through pelvic and abdominal wall collateral formation. CONCLUSIONS: Local MSC implantation induces a neovascular response resulting in a significant increase in blood flow to the ischemic limb. Marrow stromal cells are also capable of spontaneously regenerating the various components of muscular tissues.

Alam, M. M., et al. (2009). "Homocysteine reduces endothelial progenitor cells in stroke patients through apoptosis." J Cereb Blood Flow Metab 29(1): 157-165.

Homocysteine (Hcy) is a risk factor for vascular dysfunction. High levels of Hcy may result in vascular injury accelerating atherosclerosis leading to ischemia. After ischemia, endothelial progenitor cells (EPCs) migrate from bone marrow to repair damaged sites either through direct incorporation of EPCs or by repopulating mature endothelial cells. This study looks into the relationship between increased Hcy in patients with cerebrovascular disease (CVD) and EPCs. Some patients with hyperhomocysteinemia were treated with B vitamins to evaluate if the treatment reverses the elevated Hcy and its impact on their EPC levels. EPCs were treated with Hcy to determine the in vitro effects of Hcy. Our clinical findings show that elevated Hcy levels have an inverse relationship with EPC levels and B vitamin intervention can reverse this effect. Our in vitro work shows that Hcy-mediated EPC toxicity is due to apoptosis involving caspase-8, cytochrome c release, and caspase-3 activation. Vitamin B(6), and B(9) significantly impair Hcy-mediated EPC caspase-3 activation in vitro. Our clinical and in vitro data together indicate that increased Hcy results in a decrease in EPC numbers. This decrease in EPC by Hcy may be occurring through increased apoptosis and B vitamins (B(6), B(9)) intervention can attenuate such effects.

Albano, J. J. and R. W. Alexander (2011). "Autologous fat grafting as a mesenchymal stem cell source and living bioscaffold in a patellar tendon tear." Clin J Sport Med 21: 359-361.

Alderman, D. D. and R. W. Alexander (2011). "Advances in regenerative medicine: High-density platelet-rich plasma and stem cell prolotherapy for musculoskeletal pain." Practice Pain Management: 49-63, 90.

Alderman, D. D. and R. W. Alexander (2011). "Advances in stem cell therapy: Application to veterinary medicine." Today's Veterinary Practice July/August: 23-29.

Alderman, D. D., et al. (2011). "Stem cell prolotherapy in regenerative medicine." Journal of Prolotherapy 3(3): 689-708.

Alexander, R. W. (2011). "Autologous fat grafts as mesenchymal stromal stem cell source for use in prolotherapy: A simple technique to acquire lipoaspirants." Journal of Prolotherapy 3(3): 680-688.

Alexander, R. W. and D. B. Harrell (2013). "Autologous fat grafting: use of closed syringe microcannula system for enhanced autologous structural grafting."

Amann, B., et al. (2009). "[Autologous bone-marrow stem-cell transplantation for induction of arteriogenesis for limb salvage in critical limb ischaemia]." Zentralbl Chir 134(4): 298-304.

BACKGROUND: Bone marrow cell transplantation has been shown to induce angiogenesis and thus improve ischaemic artery disease. This study evaluates the effects of intramuscular bone marrow cell transplantation in patients with limb-threatening critical limb ischaemia with a very high risk for major amputation. METHODS AND RESULTS: After failed or impossible operative and / or interventional revascularisation and after unsuccessful maximum conservative therapy, 51 patients with impending major amputation due to severe critical limb ischaemia had autologous bone marrow cells (BMC) transplant-ed into the ischaemic leg. Patients 1-12 received Ficoll-isolated bone marrow mononuclear cells (total cell number 1.1 +/- 1.1 x 10(9)), patients 13-51 received point of care isolated bone marrow total nucleated cells (3.0 +/- 1.7 x 10(9)). Limb salvage was 59 % at 6 months and 53 % at last follow-up (mean: 411 +/- 261 days, range: 175-1186 days). Perfusion measured with the ankle-brachial-index (ABI) and transcutaneous oxygen tension (tcpO2) at baseline and after 6 months increased in -patients with consecutive limb salvage (ABI 0.33 +/- 0.18 to 0.46 +/- 0.15, tcpO2 12 +/- 12 to 25 +/- 15 mmHg) and did not change in patients eventually undergoing major amputation. No differences in clinical outcome between the isolation methods were seen. Clinically most important, patients with limb salvage improved from a mean Rutherford category of 4.9 at baseline to 3.3 at 6 months (p = 0.0001). Analgesics consumption was reduced by 62 %. -Total walking distance improved in non-amputees from zero to 40 metres. Three severe peri-procedural adverse events resolved without sequelae, and no unexpected long-term adverse events occurred. CONCLUSIONS: In no-option patients with end-stage critical limb ischaemia due to peripheral -artery disease, bone marrow cell transplantation is a safe procedure which can improve leg perfusion sufficiently to reduce major amputations and permit durable limb salvage.

Amann, B., et al. (2009). "Autologous bone marrow cell transplantation increases leg perfusion and reduces amputations in patients with advanced critical limb ischemia due to peripheral artery disease." Cell Transplant 18(3): 371-380.

Bone marrow cell transplantation has been shown to induce angiogenesis and thus improve ischemic artery disease. This study evaluates the effects of intramuscular bone marrow cell transplantation in patients with limb-threatening critical limb ischemia with a very high risk for major amputation. After failed or impossible operative and/or interventional revascularization and after unsuccessful maximum conservative therapy, 51 patients with impending major amputation due to severe critical limb ischemia had autologous bone marrow cells (BMC) transplanted into the ischemic leg. Patients 1-12 received Ficoll-isolated bone marrow mononuclear cells (total cell number 1.1 +/- 1.1 x 10(9)), patients 13-51 received point of care isolated bone marrow total nucleated cells (3.0 +/- 1.7 x 10(9)). Limb salvage was 59% at 6 months and 53% at last follow-up (mean 411 +/- 261 days, range 175-1186). Perfusion measured with ankle-brachial index (ABI) and transcutaneous oxygen tension (tcpO(2)) at baseline and after 6 months increased in patients with consecutive limb salvage (ABI 0.33 +/- 0.18 to 0.46 +/- 0.15, tcpO(2) 12 +/- 12 to 25 +/- 15 mmHg) and did not change in patients eventually undergoing major amputation. No difference in clinical outcome between the isolation methods were seen. Clinically most important, patients with limb salvage improved from a mean Rutherford category of 4.9 at baseline to 3.3 at 6 months (p = 0.0001). Analgesics consumption was reduced by 62%. Total walking distance improved in nonamputees from zero to 40 m. Three severe periprocedural adverse events resolved without sequelae, and no unexpected long-term adverse events occurred. In no-option patients with end-stage critical limb ischemia due to peripheral artery disease, bone marrow cell transplantation is a safe procedure that can improve leg perfusion sufficiently to reduce major amputations and permit durable limb salvage.

Andrade, M. G., et al. (2008). "Evaluation of factors that can modify platelet-rich plasma properties." Oral Surg Oral Med Oral Pathol Oral Radiol Endod 105(1): e5-e12.

OBJECTIVE: The aim of this article is to discuss a protocol for obtaining platelet-rich plasma (PRP) and evaluate which factors, derived from its preparation method and from whole blood, modify PRP cytometry and coagulation time. STUDY DESIGN: Whole blood, harvested from 50 rabbits, was centrifuged at 300g for 10 minutes. Supernatant was recentrifuged at 5000g for 5 minutes. PRP was clotted with calcium chloride. Whole blood and PRP cytometry were obtained through automatic measurement. The amount of erythrocyte- and platelet-poor plasma drawn from whole blood was measured. Hematocrit, platelet and leukocyte count, mean corpuscular volume (MCV) and mean platelet volume (MPV), mean, standard deviation, and median were also calculated at whole blood and PRP. PRP coagulation time was also analyzed. Mean values between groups were analyzed using Student t test. Correlations were evaluated using Pearson's correlation coefficient. The significance level was set at P < .05. A linear regression was performed to investigate the relationship among the correlated variables. RESULTS: From whole blood, 2.68 mL of erythrocytes and 5.72 mL of platelet-poor plasma (PPP) were removed. PRP platelet count was 2,324,080 cells/microL. Whole blood hematocrit influenced the amount of cells and PPP removed, as well as PRP platelet count. PRP platelet count was dependent on whole blood hematocrit and platelet count, and does not interfere in PRP coagulation time. A linear interaction was confirmed between the variables that presented significant Pearson correlation. CONCLUSIONS: The protocol evaluated produces a good PRP. Whole-blood parameters can predict PRP features. Whole-blood hematocrit is an important variable for PRP preparation and PRP cytometry characterization. PRP platelet count is dependent upon whole-blood platelet count.

Anversa, P., et al. (2004). "Circulating progenitor cells: search for an identity." Circulation 110(20): 3158-3160.

Armitage, J. O. (1994). "Bone marrow transplantation." N Engl J Med 330(12): 827-838.

Asahara, T., et al. (1999). "Bone marrow origin of endothelial progenitor cells responsible for postnatal vasculogenesis in physiological and pathological neovascularization." Circ Res 85(3): 221-228.

Circulating endothelial progenitor cells (EPCs) have been isolated in peripheral blood of adult species. To determine the origin and role of EPCs contributing to postnatal vasculogenesis, transgenic mice constitutively expressing beta-galactosidase under the transcriptional regulation of an endothelial cell-specific promoter (Flk-1/LZ or Tie-2/LZ) were used as transplant donors. Localization of EPCs, indicated by flk-1 or tie-2/lacZ fusion transcripts, were identified in corpus luteal and endometrial neovasculature after inductive ovulation. Mouse syngeneic colon cancer cells (MCA38) were implanted subcutaneously into Flk-1/LZ/BMT (bone marrow transplantation) and Tie-2/LZ/BMT mice; tumor samples harvested at 1 week disclosed abundant flk-1/lacZ and tie-2/lacZ fusion transcripts, and sections stained with X-gal demonstrated that the neovasculature of the developing tumor frequently comprised Flk-1- or Tie-2-expressing EPCs. Cutaneous wounds examined at 4 days and 7 days after skin removal by punch biopsy disclosed EPCs incorporated into foci of neovascularization at high frequency. One week after the onset of hindlimb ischemia, lacZ-positive EPCs were identified incorporated into capillaries among skeletal myocytes. After permanent ligation of the left anterior descending coronary artery, histological samples from sites of myocardial infarction demonstrated incorporation of EPCs into foci of neovascularization at the border of the infarct. These findings indicate that postnatal neovascularization does not rely exclusively on sprouting from preexisting blood vessels (angiogenesis); instead, EPCs circulate from bone marrow to incorporate into and thus contribute to postnatal physiological and pathological neovascularization, which is consistent with postnatal vasculogenesis.

Asahara, T., et al. (1997). "Isolation of putative progenitor endothelial cells for angiogenesis." Science 275(5302): 964-967.

Putative endothelial cell (EC) progenitors or angioblasts were isolated from human peripheral blood by magnetic bead selection on the basis of cell surface antigen expression. In vitro, these cells differentiated into ECs. In animal models of ischemia, heterologous, homologous, and autologous EC progenitors incorporated into sites of active angiogenesis. These findings suggest that EC progenitors may be useful for augmenting collateral vessel growth to ischemic tissues (therapeutic angiogenesis) and for delivering anti- or pro-angiogenic agents, respectively, to sites of pathologic or utilitarian angiogenesis.

Assmus, B., et al. (2010). "Red blood cell contamination of the final cell product impairs the efficacy of autologous bone marrow mononuclear cell therapy." J Am Coll Cardiol 55(13): 1385-1394.

OBJECTIVES: The aim of this study was to identify an association between the quality and functional activity of bone marrow-derived progenitor cells (BMCs) used for cardiovascular regenerative therapies and contractile recovery in patients with acute myocardial infarction included in the placebo-controlled REPAIR-AMI (Reinfusion of Enriched Progenitor cells And Infarct Remodeling in Acute Myocardial Infarction) trial. BACKGROUND: Isolation procedures of autologous BMCs might affect cell functionality and therapeutic efficacy. METHODS: Quality of cell isolation was assessed by measuring the total number of isolated BMCs, CD34+ and CD133+ cells, their colony-forming unit (CFU) and invasion capacity, cell viability, and contamination of the final BMC preparation with thrombocytes and red blood cells (RBCs). RESULTS: The number of RBCs contaminating the final cell product significantly correlated with reduced recovery of left ventricular ejection fraction 4 months after BMC therapy (p = 0.007). Higher numbers of RBCs in the BMC preparation were associated with reduced BMC viability (r = -0.23, p = 0.001), CFU capacity (r = -0.16, p = 0.03), and invasion capacity (r = -0.27, p < 0.001). To assess a causal role for RBC contamination, we coincubated isolated BMCs with RBCs for 24 h in vitro. The addition of RBCs dose-dependently abrogated migratory capacity (p = 0.003) and reduced CFU capacity (p < 0.05) of isolated BMCs. Neovascularization capacity was significantly impaired after infusion of BMCs contaminated with RBCs, compared with BMCs alone (p < 0.05). Mechanistically, the addition of RBCs was associated with a profound reduction in mitochondrial membrane potential of BMCs. CONCLUSIONS: Contaminating RBCs affects the functionality of isolated BMCs and determines the extent of left ventricular ejection fraction recovery after intracoronary BMC infusion in patients with acute myocardial infarction. These results suggest a bioactivity response relationship very much like a dose-response relationship in drug trials. (Reinfusion of Enriched Progenitor cells and Infarct Remodeling in Acute Myocardial Infarction [REPAIR-AMI]; NCT00279175).

Badami, E., et al. (2011). "Defective differentiation of regulatory FoxP3+ T cells by small-intestinal dendritic cells in patients with type 1 diabetes." Diabetes 60(8): 2120-2124.

OBJECTIVE: The gut environment modulates the pathogenesis of type 1 diabetes (T1D), but how it affects autoimmunity toward pancreatic beta-cells, a self-tissue located outside the intestine, is still unclear. In the small intestine, lamina propria dendritic cells (LPDCs) induce peripheral differentiation of FoxP3(+) regulatory T (Treg) cells. We tested the hypothesis that the intestinal milieu impinges on human T1D by affecting differentiation of FoxP3(+) Treg cells. RESEARCH DESIGN AND METHODS: We collected duodenal biopsies of 10 T1D patients, 16 healthy subjects, and 20 celiac individuals and performed a fluorescent-activated cell sorter analysis to measure percentages of various immune cell subsets, including CD4(+) and CD8(+) T cells, NK cells, gammadelta T cells, CD103(+)CD11c(+) LPDCs, and CD4(+)CD25(+)FoxP3(+)CD127(-) Treg cells. In parallel, we assessed the tolerogenic function (i.e., capacity to induce differentiation of FoxP3(+) Treg cells) by LPDCs of T1D patients and control subjects. RESULTS: Our analysis revealed a significant reduction in the percentage of intestinal CD4(+)CD25(+)FoxP3(+)CD127(-) Treg cells in T1D patients compared with healthy subjects (P = 0.03) and celiac individuals (P = 0.003). In addition, we found that LPDCs from T1D patients completely lacked their tolerogenic function; they were unable to convert CD4(+)CD25(-) T cells into CD4(+)CD25(+)FoxP3(+)CD127(-) Treg cells. CONCLUSIONS: Our data indicate that T1D patients have a reduced number of intestinal FoxP3(+) Treg cells as a result of their defective differentiation in the gut. These findings suggest that intestinal immune regulation is not only calibrated to tolerate commensal bacteria and food components but also is instrumental in maintaining immune tolerance toward pancreatic beta-cells and preventing T1D.

Bannenberg, G. L., et al. (2005). "Molecular circuits of resolution: formation and actions of resolvins and protectins." J Immunol 174(7): 4345-4355.

The cellular events underlying the resolution of acute inflammation are not known in molecular terms. To identify anti-inflammatory and proresolving circuits, we investigated the temporal and differential changes in self-resolving murine exudates using mass spectrometry-based proteomics and lipidomics. Key resolution components were defined as resolution indices including Psi(max), the maximal neutrophil numbers that are present during the inflammatory response; T(max), the time when Psi(max) occurs; and the resolution interval (R(i)) from T(max) to T(50) when neutrophil numbers reach half Psi(max). The onset of resolution was at approximately 12 h with proteomic analysis showing both haptoglobin and S100A9 levels were maximal and other exudate proteins were dynamically regulated. Eicosanoids and polyunsaturated fatty acids first appeared within 4 h. Interestingly, the docosahexaenoic acid-derived anti-inflammatory lipid mediator 10,17S-docosatriene was generated during the R(i). Administration of aspirin-triggered lipoxin A(4) analog, resolvin E1, or 10,17S-docosatriene each either activated and/or accelerated resolution. For example, aspirin-triggered lipoxin A(4) analog reduced Psi(max), resolvin E1 decreased both Psi(max) and T(max), whereas 10,17S-docosatriene reduced Psi(max), T(max), and shortened R(i). Also, aspirin-triggered lipoxin A(4) analog markedly inhibited proinflammatory cytokines and chemokines at 4 h (20-50% inhibition), whereas resolvin E1 and 10,17S-docosatriene's inhibitory actions were maximal at 12 h (30-80% inhibition). Moreover, aspirin-triggered lipoxin A(4) analog evoked release of the antiphlogistic cytokine TGF-beta. These results characterize the first molecular resolution circuits and their major components activated by specific novel lipid mediators (i.e., resolvin E1 and 10,17S-docosatriene) to promote resolution.

Barou, O., et al. (2002). "Relationships between trabecular bone remodeling and bone vascularization: a quantitative study." Bone 30(4): 604-612.

Beside its well-known role in bone development, vascularization plays a major role in bone cell migration for bone remodeling and metastatic tumor invasion. However, the various techniques used to identify vessels in bone have never been tested for trabecular bone vessel quantification, whereas bone remodeling quantitative parameters are commonly assessed. In this context, we developed and compared various histological techniques used to visualize blood vessels in rat bone in order to quantify them. First, several products were tested by intracardiac infusion to opacify the bone vascular network. The best results were obtained using either an India ink-1% agarose solution or an India ink-saturated barium sulfate solution followed by X-ray microradiography. Second, to identify the types of vessels, we also performed histoenzymology and immunohistochemistry stainings. Neither alkaline phosphatase (for endothelial cells) nor adenosine triphosphatase (ATPase) stainings (for smooth muscle cells) provided a low enough background to allow for vessel identification and quantification. For immunohistochemistry, various specific vessel constituents were analyzed: laminin, smooth muscle cell alpha-actin, factor VIII, and lectin Griffonia simplifolia. Anti-laminin and anti-smooth muscle cell alpha-actin antibodies gave the best results for quantification. Third, after optimization of these techniques, we performed quantitative bone and vessel histomorphometry on two groups of 12 rats each, for which bone remodeling and vessel number and area parameters were measured. No statistical differences were observed between the two groups, confirming the reproducibility of our measurements. A significant relationship was found between vessel number and histodynamic parameters; that is, bone formation rate correlated positively with India ink-positive vessel area (p < 0.009, r2 = 0.54) and alpha-actin-positive vessel number (p < 0.05, r2 = 0.66). Furthermore, we report reproducible techniques for visualization and quantification of vessels in bone that also allowed for simultaneous conventional bone histomorphometry. This methodology should help researchers to better understand the functional and anatomical relationship between trabecular bone and its vascularization during normal or pathological processes.

Barth, A. (1893). "Ueber histologische Befunde nach Knochenimplantationen." Arch Klin Chir 46: 409-417.

Becker, A. J., et al. (1963). "Cytological demonstration of the clonal nature of spleen colonies derived from transplanted mouse marrow cells." Nature 197: 452-454.

Bhattacharya, V., et al. (2000). "Enhanced endothelialization and microvessel formation in polyester grafts seeded with CD34(+) bone marrow cells." Blood 95(2): 581-585.

The authors have shown accelerated endothelialization on polyethylene terephthalate (PET) grafts preclotted with autologous bone marrow. Bone marrow cells have a subset of early progenitor cells that express the CD34 antigen on their surfaces. A recent in vitro study has shown that CD34(+) cells can differentiate into endothelial cells. The current study was designed to determine whether CD34(+) progenitor cells would enhance vascular graft healing in a canine model. The authors used composite grafts implanted in the dog's descending thoracic aorta (DTA) for 4 weeks. The 8-mm x 12-cm composite grafts had a 4-cm PET graft in the center and 4-cm standard ePTFE grafts at each end. The entire composite was coated with silicone rubber to make it impervious; thus, the PET segment was shielded from perigraft and pannus ingrowth. There were 5 study grafts and 5 control grafts. On the day before surgery, 120 mL bone marrow was aspirated, and CD34(+) cells were enriched using an immunomagnetic bead technique, yielding an average of 11.4 +/- 5. 3 x 10(6). During surgery, these cells were mixed with venous blood and seeded onto the PET segment of composite study grafts; the control grafts were treated with venous blood only. Hematoxylin and eosin, immunocytochemical, and AgNO(3 )staining demonstrated significant increases of surface endothelialization on the seeded grafts (92% +/- 3.4% vs 26.6% +/- 7.6%; P =.0001) with markedly increased microvessels in the neointima, graft wall, and external area compared with controls. In dogs, CD34(+) cell seeding enhances vascular graft endothelialization; this suggests practical therapeutic applications. (Blood. 2000;95:581-585)

Bignold, L. P. (1980). "Importance of platelets in increased vascular permeability evoked by experimental haemarthrosis in synovium of the rat." Pathology 12(2): 169-179.

Increased vascular permeability of synovium induced by experimental haemarthrosis was studied in the stifle joint of the rat. Abnormal permeability was detected by injecting animals intravenously with colloidal carbon and examining the synovial vessels for intramural deposits of carbon. Both fresh and heparinized whole blood injected into the joint induced a marked permeability response of synovial venules which persisted for 18 hours. Platelets suspended in heparinized Tyrode solution induced a similar response, but one lasting only 12 hours. The permeability effects of suspensions of leucocytes and erythrocytes on the synovial vasculature were relatively mild and were maximal 5 and 12 h respectively after intra-articular injection. Heparinized platelet-free plasma had no significant permeability effects. These results indicate that platelets may play an important role in the pathogenesis of synovial inflammation in haemarthrosis.

Boden, S. D., et al. (2000). "The use of rhBMP-2 in interbody fusion cages. Definitive evidence of osteoinduction in humans: a preliminary report." Spine (Phila Pa 1976) 25(3): 376-381.

STUDY DESIGN: A prospective randomized controlled human clinical pilot trial. OBJECTIVES: To determine the feasibility of using rhBMP-2/collagen as a substitute for autogenous bone graft inside interbody fusion cages to achieve arthrodesis in humans. SUMMARY OF BACKGROUND DATA: Preclinical studies have shown rhBMP-2 to be an effective substitute for autogenous bone graft, but there are no studies to date documenting such efficacy for human spine fusion. METHODS: Fourteen patients with single-level lumbar degenerative disc disease refractory to nonoperative management were randomized to receive lumbar interbody arthrodesis with a tapered cylindrical threaded fusion cage filled with rhBMP-2/collagen sponge or autogenous iliac crest bone. Patients were evaluated with radiographs, sagittally reformatted computed tomography scans, and Short Form-36 and Oswestry outcome questionnaires. RESULTS: All 11 patients who received rhBMP-2 were judged by three independent radiologists to have solid fusions (at 6, 12, and 24 months postimplantation), whereas only 2 of the 3 control patients, who received the standard treatment of autogenous iliac crest bone, were deemed to be fused. The Oswestry Disability Questionnaire scores of the rhBMP-2 group improved sooner (after 3 months) than those of the autograft group, with both groups demonstrating similar improvement at 6 months. Short Form 36 scores continued to improve up to 24 months. CONCLUSION: The arthrodesis was found to occur more reliably in patients treated with rhBMP-2-filled fusion cages than in controls treated with autogenous bone graft, although the sample size was limited. There were no adverse events related to the rhBMP-2 treatment. This study is one of the first to show consistent and unequivocal osteoinduction by a recombinant growth factor in-humans.

Bonfanti, P., et al. (2012). "'Hearts and bones': the ups and downs of 'plasticity' in stem cell biology." EMBO Mol Med 4(5): 353-361.

More than a decade ago, 'plasticity' suddenly became a 'fashionable' topic with overemphasized implications for regenerative medicine. The concept of 'plasticity' is supported by old transplantation work, at least for embryonic cells, and metaplasia is a classic example of plasticity observed in patients. Nevertheless, the publication of a series of papers showing rare conversion of a given cell type into another unrelated cell raised the possibility of using any unaffected tissue to create at will new cells to replace a different failing tissue or organ. This resulted in disingenuous interpretations and a reason not to fund anymore research on embryonic stem cells (ESc). Moreover, many papers on plasticity were difficult to reproduce and thus questioned; raising issues about plasticity as a technical artefact or a consequence of rare spontaneous cells fusion. More recently, reprogramming adult differentiated cells to a pluripotent state (iPS) became possible, and later, one type of differentiated cell could be directly reprogrammed into another (e.g. fibroblasts into neurons) without reverting to pluripotency. Although the latter results from different and more robust experimental protocols, these phenomena also exemplify 'plasticity'. In this review, we want to place 'plasticity' in a historical perspective still taking into account ethical and political implications.

Borenstain, M., et al. (2007). "Introduction to meta-analysis." Retrieved December 1, 2011, from http://www.meta-analysis.com/downloads/Meta%20Analysis%20Fixed%20vs%20Random%20effects.pdf.

Bouletreau, P. J., et al. (2002). "Hypoxia and VEGF up-regulate BMP-2 mRNA and protein expression in microvascular endothelial cells: implications for fracture healing." Plast Reconstr Surg 109(7): 2384-2397.

The endothelium is a metabolically active secretory tissue, capable of responding to a wide array of environmental stimuli. Hypoxia and vascular endothelial growth factor (VEGF) are two components of the putative fracture microenvironment. This study investigated the role of hypoxia and VEGF on endothelial cell activation as it relates to the bone repair process. It was hypothesized that endothelial cells may have an important osteogenic role in fracture healing through the production of bone morphogenetic protein-2 (BMP-2), an osteogenic cytokine at the fracture site. Therefore, BMP-2 mRNA and protein expression in endothelial cells under hypoxia and/or VEGF treatment was studied. The authors observed a 2-fold to 3-fold up-regulation of BMP-2 mRNA expression in bovine capillary endothelial cells and human microvascular endothelial cells stimulated with hypoxia or rhVEGF. Furthermore, the combined effects of hypoxia and rhVEGF appeared to be additive on BMP-2 mRNA expression in bovine capillary endothelial cells. Actinomycin D and cycloheximide studies suggested that the increased mRNA expression was transcriptionally regulated. BMP-2 protein expression was up-regulated after 24 and 48 hours of treatment with either hypoxia or rhVEGF in bovine capillary endothelial cells. Surprisingly, the data suggest that endothelial cells may play not only an angiogenic role but also an osteogenic role by a direct stimulation of the osteoblasts, through the enhanced expression of a potent osteogenic factor, BMP-2, at the fracture site.

Burkus, J. K., et al. (2002). "Anterior lumbar interbody fusion using rhBMP-2 with tapered interbody cages." J Spinal Disord Tech 15(5): 337-349.

In a multicenter, prospective, randomized, nonblinded, 2-year study, 279 patients with degenerative lumbar disc disease were randomly divided into two groups that underwent interbody fusion using two tapered threaded fusion cages. The investigational group (143 patients) received rhBMP-2 on an absorbable collagen sponge, and a control group (136 patients) received autogenous iliac crest bone graft. Plain radiographs and computed tomographic scans were used to evaluate fusion at 6, 12, and 24 months after surgery. Mean operative time (1.6 hours) and blood loss (109.8 mL) were less in the investigational rhBMP-2 group than in the autograft control group (2.0 hours and 153.1 mL). At 24 months the investigational group's fusion rate (94.5%) remained higher than that of the control group (88.7%). New bone formation occurred in all investigational patients. At all intervals, mean postoperative Oswestry, back pain, and leg pain scores and neurologic status improved in both treatment groups with similar outcomes. In the control group, eight adverse events related to the iliac crest graft harvest occurred (5.9%), and at 24 months 32% of patients reported graft site discomfort and 16% were bothered by its appearance. Lumbar fusion using rhBMP-2 and a tapered titanium fusion cage can yield a solid union and eliminate the need for harvesting iliac crest bone graft.

Burkus, J. K., et al. (2003). "Is INFUSE bone graft superior to autograft bone? An integrated analysis of clinical trials using the LT-CAGE lumbar tapered fusion device." J Spinal Disord Tech 16(2): 113-122.

Multicenter human clinical studies of patients undergoing anterior lumbar fusion have been conducted using recombinant bone morphogenetic protein or rhBMP-2 on an absorbable collagen sponge, marketed as INFUSE Bone Graft, or autograft implanted in the LT-CAGE Lumbar Tapered Fusion device. An integrated analysis of multiple clinical studies was performed using an analysis of covariance to adjust for preoperative variables in a total of 679 patients. Of these patients, 277 had their cages implanted with rhBMP-2 on an absorbable collagen sponge and 402 received autograft transferred from the iliac crest. The patients treated with rhBMP-2 had statistically superior outcomes with regard to length of surgery, blood loss, hospital stay, reoperation rate, median time to return to work, and fusion rates at 6, 12, and 24 months. Oswestry Disability Index scores and the Physical Component Scores and Pain Index of the SF-36 scale at 3, 6, 12, and 24 months showed statistically superior outcomes in the rhBMP-2 group.

Burkus, J. K., et al. (2005). "Use of rhBMP-2 in combination with structural cortical allografts: clinical and radiographic outcomes in anterior lumbar spinal surgery." J Bone Joint Surg Am 87(6): 1205-1212.

BACKGROUND: Recombinant human bone morphogenetic protein-2 soaked into an absorbable collagen sponge (rhBMP-2/ACS) has been shown in a nonhuman primate study and in a pilot study in humans to promote new bone formation and incorporation of an allograft device when implanted in patients undergoing anterior lumbar interbody arthrodesis. However, a larger series with longer follow-up is needed to demonstrate its superiority to autogenous iliac crest bone graft. METHODS: Between 1998 and 2001, a two-part, prospective, randomized, multicenter study of 131 patients was conducted to determine the safety and efficacy of the use of rhBMP-2/ACS as a replacement for autogenous iliac crest bone graft in anterior lumbar spinal arthrodesis with threaded cortical allograft dowels. Patients were randomly assigned to a study group that received rhBMP-2/ACS or to a control group that received autograft. The clinical and radiographic outcomes were determined with use of well-established instruments and radiographic assessments. RESULTS: The patients in the study group had significantly better outcomes than the control group with regard to the average length of surgery (p < 0.001), blood loss (p < 0.001), and hospital stay (p = 0.020). Fusion rates were significantly better in the study group (p < 0.001). The average Oswestry Disability Index scores, Short-Form-36 physical component summary scores, and low-back and leg-pain scores were significantly better in the study group (p < 0.05). CONCLUSIONS: In patients undergoing anterior lumbar interbody arthrodesis with threaded allograft cortical bone dowels, rhBMP-2/ACS was an effective replacement for autogenous bone graft and eliminated the morbidity associated with graft harvesting.

Burwell, R. G. (1964). "Studies in the Transplantation of Bone. Vii. The Fresh Composite Homograft-Autograft of Cancellous Bone; an Analysis of Factors Leading to Osteogenesis in Marrow Transplants and in Marrow-Containing Bone Grafts." J Bone Joint Surg Br 46: 110-140.

Butler, S., et al. (2009). "Symapthetic denervation differentially modulates direct trophic effects of VEGF on contractile differentiation in ovine fetal middle cerebral arteries." Journal of Cerebral Blood Flow & Metabolism(29): S379.

Caolo, V., et al. (2012). "Notch regulation of hematopoiesis, endothelial precursor cells, and blood vessel formation: orchestrating the vasculature." Stem Cells Int 2012: 805602.

The development of the vascular system begins with the formation of hemangioblastic cells, hemangioblasts, which organize in blood islands in the yolk sac. The hemangioblasts differentiate into hematopoietic and angioblastic cells. Subsequently, the hematopoietic line will generate blood cells, whereas the angioblastic cells will give rise to vascular endothelial cells (ECs). In response to specific molecular and hemodynamic stimuli, ECs will acquire either arterial or venous identity. Recruitment towards the endothelial tubes and subsequent differentiation of pericyte and/or vascular smooth muscle cells (vSMCs) takes place and the mature vessel is formed. The Notch signaling pathway is required for determining the arterial program of both endothelial and smooth muscle cells; however, it is simultaneously involved in the generation of hematopoietic stem cells (HSCs), which will give rise to hematopoietic cells. Notch signaling also regulates the function of endothelial progenitor cells (EPCs), which are bone-marrow-derived cells able to differentiate into ECs and which could be considered the adult correlate of the angioblast. In addition, Notch signaling has been reported to control sprouting angiogenesis during blood vessels formation in the adult. In this paper we discuss the physiological role of Notch in vascular development, providing an overview on the involvement of Notch in vascular biology from hematopoietic stem cell to adaptive neovascularization in the adult.

Caplan, A. I. (1987). "Bone development and repair." Bioessays 6(4): 171-175.

Caplan, A. I. (2010). "Meschymal stem cells: The past, the present, the future." Cartilage 1(1): 6-9.

Caplan, A. I. (2010). "What's in a name?" Tissue Eng Part A 16(8): 2415-2417.

Caplan, A. I. and J. E. Dennis (2006). "Mesenchymal stem cells as trophic mediators." J Cell Biochem 98(5): 1076-1084.

Adult marrow-derived Mesenchymal Stem Cells (MSCs) are capable of dividing and their progeny are further capable of differentiating into one of several mesenchymal phenotypes such as osteoblasts, chondrocytes, myocytes, marrow stromal cells, tendon-ligament fibroblasts, and adipocytes. In addition, these MSCs secrete a variety of cytokines and growth factors that have both paracrine and autocrine activities. These secreted bioactive factors suppress the local immune system, inhibit fibrosis (scar formation) and apoptosis, enhance angiogenesis, and stimulate mitosis and differentiation of tissue-intrinsic reparative or stem cells. These effects, which are referred to as trophic effects, are distinct from the direct differentiation of MSCs into repair tissue. Several studies which tested the use of MSCs in models of infarct (injured heart), stroke (brain), or meniscus regeneration models are reviewed within the context of MSC-mediated trophic effects in tissue repair.

Caralla, T., et al. (2011). Concentration and selection of osteogenic progenitors using magnetic labeling based on hyaluronan expression for immediate transplantation into a canine femoral multidefect model. TERMIS.

Carano, R. A. and E. H. Filvaroff (2003). "Angiogenesis and bone repair." Drug Discov Today 8(21): 980-989.

The intimate connection, both physical and biochemical, between blood vessels and bone cells has long been recognized. Genetic, biochemical, and pharmacological studies have identified and characterized factors involved in the conversation between endothelial cells (EC) and osteoblasts (OB) during both bone formation and repair. The long-awaited FDA approval of two growth factors, BMP-2 and OP-1, with angiogenic and osteogenic activity confirms the importance of these two processes in human skeletal healing. In this review, the role of osteogenic factors in the adaptive response and interactive function of OB and EC during the multi-step process of bone repair will be discussed.

Carlen, M., et al. (2009). "Forebrain ependymal cells are Notch-dependent and generate neuroblasts and astrocytes after stroke." Nat Neurosci 12(3): 259-267.

Neurons are continuously generated from stem cells in discrete regions in the adult mammalian brain. We found that ependymal cells lining the lateral ventricles were quiescent and did not contribute to adult neurogenesis under normal conditions in mice but instead gave rise to neuroblasts and astrocytes in response to stroke. Ependymal cell quiescence was actively maintained by canonical Notch signaling. Inhibition of this pathway in uninjured animals allowed ependymal cells to enter the cell cycle and produce olfactory bulb neurons, whereas forced Notch signaling was sufficient to block the ependymal cell response to stroke. Ependymal cells were depleted by stroke and failed to self-renew sufficiently to maintain their own population. Thus, although ependymal cells act as primary cells in the neural lineage to produce neurons and glial cells after stroke, they do not fulfill defining criteria for stem cells under these conditions and instead serve as a reservoir that is recruited by injury.

Carlson, B. M. (2007). Principles of Regenerative Biology. Burlington, MA, Academic Press / Elsevier.

Cavallaro, A. M., et al. (2000). "Three to six year follow-up of normal donors who received recombinant human granulocyte colony-stimulating factor." Bone Marrow Transplant 25(1): 85-89.

One hundred and one donors who had received filgrastim (rhG-CSF) for the purpose of donating either granulocytes or peripheral blood stem cells (PBSC) for their relatives more than 3 years ago were contacted. All donors had received daily rhG-CSF at a median dose of 16 microg/kg/day (range 3-16) for a median of 6 days (range 3-15 days). All collection procedures were completed and short-term side-effects of rhG-CSF were mild in the majority of the donors. At a median time interval of 43.13 months (range 35-73), the donors were contacted to assess whether adverse effects related to rhG-CSF administration had occurred. Prior to rhG-CSF two donors had cancer, one had a myocardial infarction, one was hepatitis C virus positive, one had a history of sinusitis, one had Graves' disease and two had arterial hypertension. None worsened with the rhG-CSF administration but the donor with a history of infarction had an episode of angina following apheresis, and the donor with Graves' disease had a stroke 15 months after rhG-CSF. Two pregnancies occurred after the rhG-CSF administration and one donor was 2-3 weeks pregnant during rhG-CSF treatment. Three pregnancies resulted in two normal births and one in a spontaneous abortion of a pregnancy which occurred more than 2 years following rhG-CSF. In the time following rhG-CSF administration two donors developed cancer (breast and prostate cancer) at a follow-up of 70 and 11 months, respectively. One donor developed lymphadenopathy 38 months after the rhG-CSF, which spontaneously resolved. Blood counts were obtained in 70 donors at a median follow up of 40.4 months (range 16.8-70.8). Hematocrit was 43% (median, range 36.8-48), white blood cells were 5.7 x 109/l (median, range 3-14), granulocytes 3.71 x 109/l (median, range 1. 47-10.36), lymphocytes 1.67 x 109/l (median, range 0.90-3.96), monocytes 0.46 x 109/l (median, range 0.07-0.87) and platelet counts were 193.0 x 109/l (median, range 175.0-240.0). This study indicates that short-term administration of rhG-CSF to normal donors for the purpose of mobilizing the PBSC or granulocytes appears safe and without any obvious adverse effects more than 3 years after the donation. Bone Marrow Transplantation (2000) 25, 85-89.

Ceradini, D. J. and G. C. Gurtner (2005). "Homing to hypoxia: HIF-1 as a mediator of progenitor cell recruitment to injured tissue." Trends Cardiovasc Med 15(2): 57-63.

The identification of bone marrow-derived endothelial progenitor cells has altered our understanding of new blood vessel growth and tissue regeneration. Previously, new blood vessel growth in the adult was thought to only occur through angiogenesis, the sprouting of new vessels from existing structures. However, it has become clear that circulating bone marrow-derived cells can form new blood vessels through a process of postnatal vasculogenesis, with endothelial progenitor cells selectively recruited to injured or ischemic tissue. How this process occurs has remained unclear. One common element in the different environments where vasculogenesis is believed to occur is the presence of a hypoxic stimulus. We have identified the chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 as critical mediators for the ischemia-specific recruitment of circulating progenitor cells. We have found that the endothelial expression of SDF-1 acts as a signal indicating the presence of tissue ischemia, and that its expression is directly regulated by hypoxia-inducible factor-1. Stromal cell-derived factor 1 is the only chemokine family member known to be regulated in this manner. Later events, including proliferation, patterning, and assembly of recruited progenitors into functional blood vessels, are also influenced by tissue oxygen tension and hypoxia. Interestingly, both SDF-1 and hypoxia are present in the bone marrow niche, suggesting that hypoxia may be a fundamental requirement for progenitor cell trafficking and function. As such, ischemic tissue may represent a conditional stem cell niche, with recruitment and retention of circulating progenitors regulated by hypoxia through differential expression of SDF-1.

Cesari, F., et al. (2009). "Bone marrow-derived progenitor cells in the early phase of ischemic stroke: relation with stroke severity and discharge outcome." J Cereb Blood Flow Metab 29(12): 1983-1990.

A limited number of studies suggested that in ischemic stroke patients, the number of bone marrow circulating progenitor cells (CPCs), either endothelial progenitor cells (EPCs) or CPCs, was negatively correlated with the number of infarcts as well as with the outcome. The aim of this study was to simultaneously measure CPCs and EPCs in the acute phase of ischemic stroke, and to establish whether a relationship exists with stroke severity and discharge outcome. In 67 (40 M; 27 F) ischemic stroke patients with a median age of 73 (21 to 91) years, the number of CPCs and EPCs was measured by flow cytometry and analyzed in relation to baseline NIH Stroke Scale score, ischemic stroke syndromes, and discharge outcome. Patients with partial anterior circulation syndrome showed a higher CPCs' number with respect to patients with total anterior circulation syndrome. Moreover, a negative relationship between National Institutes of Health Stroke Scale score at the admission and CPCs number was observed. When the outcome was considered, patients discharged to home had a higher number of CPCs, but not of EPCs, compared with those moved to a rehabilitation unit. We report an association between the number of CPCs measured in the early phase after stroke presentation, neurologic severity, and discharge outcome.

Chen, J. L., et al. (1997). "Osteoblast precursor cells are found in CD34+ cells from human bone marrow." Stem Cells 15(5): 368-377.

It is known that osteoblast precursor cells are found in the low-density mononuclear (LDMN) fraction of human bone marrow (BM) aspirates. The purpose of this study was to investigate whether CD34, a hematopoietic progenitor cell marker, is present on osteoblast progenitor cells. LDMN, CD34+, and CD34- cells were cultured under conditions that promote growth and differentiation of mineral-secreting osteoblasts in a limiting dilution manner. With LDMN cells, osteoblast progenitor cells were found at an average frequency of 1/36,000 cells. With CD34- cells, osteoblast progenitor frequency remained at an average of 1/33,000, similar to LDMN cells. With CD34+ selected cells, osteoblast progenitor frequency increased to an average of 1/5,000. This osteoblast progenitor frequency is maintained in sorted CD34+/CD38+ cells. The osteoblasts generated from CD34+ cells were morphologically normal, and expression of skeletal-specific alkaline phosphatase and osteonectin increased upon differentiation induced by dexamethasone (DEX) treatment. Ultrastructurally, these CD34+ cell-derived osteoblasts displayed osteoblast-specific features. Functionally, these CD34+ cell-derived osteoblasts differentiated with DEX treatment, increased the level of cyclic adenosine monophosphate in response to parathyroid hormone stimulation, increased the level of alkaline phosphatase activity, and increased mineral secretion. These results demonstrate that osteoblast progenitor cells are enriched in the CD34+ cell population from BM and that these progenitor cells can differentiate into functional osteoblasts in culture.

Choi, J., et al. (2005). "Human endothelial cells enhance human immunodeficiency virus type 1 replication in CD4+ T cells in a Nef-dependent manner in vitro and in vivo." J Virol 79(1): 264-276.

Infected CD4+ T cells are the primary sites of human immunodeficiency virus type 1 (HIV-1) replication in vivo. However, signals from professional antigen-presenting cells (APCs), such as dendritic cells and macrophages, greatly enhance HIV-1 replication in T cells. Here, we report that in cocultures, vascular endothelial cells (ECs), which in humans can also serve as APCs, can enhance HIV-1 production of both CCR5- and CXCR4-utilizing strains approximately 50,000-fold. The observed HIV-1 replication enhancement conferred by ECs occurred only in memory CD4+ T cells, required expression of major histocompatibility complex class II (MHC-II) molecules by the ECs, and could not be conferred by fixed ECs, all of which are consistent with a requirement for EC-mediated T-cell activation via T-cell receptor (TCR) signaling. Deletion of nef (Nef-) decreased HIV-1 production by approximately 100-fold in T cells cocultured with ECs but had no effect on virus production in T cells cocultured with professional APCs or fibroblasts induced to express MHC-II. Human ECs do not express B7 costimulators, but Nef- replication in CD4(+)-T-cell and EC cocultures could not be rescued by anti-CD28 antibody. ECs act in trans to enhance wild-type but not Nef- replication and facilitate enhanced wild-type replication in naive T cells when added to T-cell or B-lymphoblastoid cell cocultures, suggesting that ECs also provide a TCR-independent signal to infected T cells. Consistent with these in vitro observations, wild-type HIV-1 replicated 30- to 50-fold more than Nef- in human T cells infiltrating allogeneic human skin grafts on human huPBL-SCID/bg mice, an in vivo model of T-cell activation by ECs. Our studies suggest that ECs, which line the entire cardiovascular system and are, per force, in frequent contact with memory CD4+ T cells, provide signals to HIV-1-infected CD4+ T cells to greatly enhance HIV-1 production in a Nef-dependent manner, a mechanism that could contribute to the development of AIDS.

Chopp, M., et al. (2008). "Plasticity and remodeling of brain." J Neurol Sci 265(1-2): 97-101.

The injured brain can be stimulated to amplify its intrinsic restorative processes to improve neurological function. Thus, after stroke, both cell and pharmacological neurorestorative treatments, amplify the induction of brain neurogenesis and angiogenesis, and thereby reduce neurological deficits. In this manuscript, we describe the use of bone marrow mesenchymal cells (MSCs) and erythropoietin (EPO) as examples of cell-based and pharmacological neurorestorative treatments, respectively, for both stroke and a mouse model of experimental autoimmune encephalomyelitis (EAE). We demonstrate that these therapies significantly improve neurological function with treatment initiated after the onset of injury and concomitantly promote brain plasticity. The application of MRI to monitor changes in the injured brain associated with reduction of neurological deficit is also described.

Connolly, J., et al. (1989). "Development of an osteogenic bone-marrow preparation." J Bone Joint Surg Am 71(5): 684-691.

The osteogenic effect of bone marrow was tested in rabbits, using chambers that had been implanted in the peritoneal cavity (ectopic site) and in a delayed-union model (orthotopic site). Osteogenesis was accelerated in both sites after concentration of marrow elements by centrifugation, but not after unit gravity sedimentation. Chambers that were implanted with marrow that had been processed by simple and isopyknic centrifugation demonstrated a more pronounced increase in deposition of calcium compared with whole-marrow implants of equal volume (101 compared with 193 per cent). Orthotopic grafting of a rabbit delayed-union model with whole marrow and marrow that had been processed with simple centrifugation significantly increased osteogenesis, as measured biomechanically and biochemically. Significantly improved healing was evident radiographically at five weeks after grafting with bone marrow that had been concentrated by simple centrifugation.

Connolly, J. F. (1998). "Clinical use of marrow osteoprogenitor cells to stimulate osteogenesis." Clin Orthop Relat Res(355 Suppl): S257-266.

This review of 15 years research into various methods and techniques of using marrow osteoprogenitor cells shows that marrow grafts can be useful for numerous skeletal healing problems, but not all. The method offers considerable improvement over standard open iliac crest grafting and provides an attractive and advantageous method of stimulating osteogenesis in the management and prevention of nonunion.

Connolly, J. F., et al. (1991). "Autologous marrow injection as a substitute for operative grafting of tibial nonunions." Clinical Orthopaedics and Related Research 266: 259-270.

Cornejo, A., et al. (2012). "Effect of adipose tissue-derived osteogenic and endothelial cells on bone allograft osteogenesis and vascularization in critical-sized calvarial defects." Tissue Eng Part A.

The use of processed bone allograft to repair large osseous defects of the skull has been limited given that it lacks the osteogenic cellularity and intrinsic vascular supply which are essential elements for successful graft healing and, at the same time, the areas to be targeted through tissue engineering applications. In this study we investigated the effect of predifferentiated rat adipose tissue derived osteoblastic cells (OBs) and endothelial cells (ECs) on calvarial bone allograft healing and vascularization using an orthotopic critical-sized calvarial defect model. For this purpose, thirty-seven 8 mm critical calvarial defects in Lewis rats were treated with bone allografts seeded with: no cells, undifferentiated adipose stem cells (ASC), OBs, ECs, and OBs and ECs simultaneously. After 8 weeks the bone volume and mineral density were calculated using micro computed tomography and the microvessel formation using immunohistochemical staining and imaging software. The amount of bone within the 8 mm defect was significantly higher for the allografts treated ECs compared to the allografts treated with OBs (p= 0.05) and with the two cell lineages simultaneously (p= 0.02). There were no significant differences in bone formation between the latter two groups and the control groups (allografts treated with no cells and undifferentiated ASC). There were no significant differences in bone mineral density among the groups. The amount of microvessels was significantly higher in the group treated with ECs relative to all groups (p= <0.05). Our results show that the implantation of ASC derived ECs improves the vascularization of calvarial bone allografts at 8 weeks after treatment. This cell based vascularization strategy can be used to improve the paucity of perfusion in allogenic bone implants. However, in this study the treatment of allografts with OBs alone or in combination with ECs did not support bone formation or vascularization.

Cristancho, A. G. and M. A. Lazar (2011). "Forming functional fat: a growing understanding of adipocyte differentiation." Nat Rev Mol Cell Biol 12(11): 722-734.

Adipose tissue, which is primarily composed of adipocytes, is crucial for maintaining energy and metabolic homeostasis. Adipogenesis is thought to occur in two stages: commitment of mesenchymal stem cells to a preadipocyte fate and terminal differentiation. Cell shape and extracellular matrix remodelling have recently been found to regulate preadipocyte commitment and competency by modulating WNT and RHO-family GTPase signalling cascades. Adipogenic stimuli induce terminal differentiation in committed preadipocytes through the epigenomic activation of peroxisome proliferator-activated receptor-gamma (PPARgamma). The coordination of PPARgamma with CCAAT/enhancer-binding protein (C/EBP) transcription factors maintains adipocyte gene expression. Improving our understanding of these mechanisms may allow us to identify therapeutic targets against metabolic diseases that are rapidly becoming epidemic globally.

Daar, A. S. and H. L. Greenwood (2007). "A proposed definition of regenerative medicine." J Tissue Eng Regen Med 1(3): 179-184.

There exists a lack of consensus regarding a clear and precise definition of regenerative medicine. We suggest here a definition developed by the authors with input from researchers in the various contributing disciplines. This definition emphasizes the interdisciplinarity of the field, its goal of restoring impaired function, and the wide variety of technologies that can contribute to achieving this goal. By highlighting the lack of agreement regarding a definition of regenerative medicine, and by proposing our own definition, we hope to stimulate discussion on the subject within the field and to encourage the regenerative medicine community to work together to develop a consensus definition. We believe that a clear definition of regenerative medicine could help to unify the field and is essential to facilitate understanding among policy makers, funding agencies and the general public, as well as individuals from scientific and medical disciplines.

Daley, G. Q. (2009). Hematopoietic stem cells. Essentials of Stem Cell Biology. San Diego, CA, Elsevier: 211-215.

Dar, A., Gerecht-Nir, S., Itskovitz-Eldor, J. (2009). Human vascular progenitor cells. Stem Cell Biology. San Diego, CA, Elsevier: 227-232.

Dar, A., et al. (2009). Interactions between hematopoietic stem/progenitor cells and the bone marrow: The biology of stem cell homing and mobilization. Hematology: Basic Principles and Practice. R. Hoffman, E. J. J. Benz, S. J. Shattil et al. Philadelphia, PA, Churchill Livingstone Elsevier: 245-252.

de Boer, H. C., et al. (2006). "Fibrin and activated platelets cooperatively guide stem cells to a vascular injury and promote differentiation towards an endothelial cell phenotype." Arterioscler Thromb Vasc Biol 26(7): 1653-1659.

OBJECTIVE: Bone marrow-derived progenitor cells play a role in vascular regeneration. However, their homing to areas of vascular injury is poorly understood. One of the earliest responses to an injury is the activation of coagulation and platelets. In this study we assessed the role of hemostatic components in the recruitment of CD34+ cells to sites of injury. METHODS AND RESULTS: Using an ex vivo injury model, representing endothelial cell (EC) injury or vessel denudation, we studied homing of CD34+ under flow. Platelet aggregates facilitated initial tethering and rolling of CD34+ cells through interaction of P-selectin expressed by platelets and P-selectin glycoprotein ligand-1 (PSGL-1), expressed by CD34+ cells. Ligation of PSGL-1 activated adhesion molecules on CD34+ cells, ultimately leading to firm adhesion of CD34+ cells to tissue factor-expressing ECs or to fibrin-containing thrombi formed on subendothelium. We also demonstrate that fibrin-containing thrombi can support migration of CD34+ cells to the site of injury and subsequent differentiation toward a mature EC phenotype. Additionally, intravenously injected CD34+ cells homed in vivo to denuded arteries in the presence of endogenous leukocytes. CONCLUSIONS: We provide evidence that hemostatic factors, associated with vascular injury, provide a regulatory microenvironment for re-endothelialization mediated by circulating progenitor cells.

De Gruttola, S., et al. (2005). "Computational simulation of the blood separation process." Artif Organs 29(8): 665-674.

The aim of this work is to construct a computational fluid dynamics model capable of simulating the quasitransient process of apheresis. To this end a Lagrangian-Eulerian model has been developed which tracks the blood particles within a delineated two-dimensional flow domain. Within the Eulerian method, the fluid flow conservation equations within the separator are solved. Taking the calculated values of the flow field and using a Lagrangian method, the displacement of the blood particles is calculated. Thus, the local blood density within the separator at a given time step is known. Subsequently, the flow field in the separator is recalculated. This process continues until a quasisteady behavior is reached. The simulations show good agreement with experimental results. They shows a complete separation of plasma and red blood cells, as well as nearly complete separation of red blood cells and platelets. The white blood cells build clusters in the low concentrate cell bed.

Deyo, R. A., et al. (2012). "Use of bone morphogenetic proteins in spinal fusion surgery for older adults with lumbar stenosis: trends, complications, repeat surgery, and charges." Spine (Phila Pa 1976) 37(3): 222-230.

STUDY DESIGN: Retrospective cohort study of Medicare claims. OBJECTIVE: Examine trends and patterns in the use of bone morphogenetic proteins (BMP) in surgery for lumbar stenosis; compare complications, reoperation rates, and charges for patients undergoing lumbar fusion with and without BMP. SUMMARY OF BACKGROUND DATA: Small, randomized trials have demonstrated higher rates of solid fusion with BMP than with allograft bone alone, with few complications and, in some studies, reduced rates of revision surgery. However, complication and reoperation rates from large population-based cohorts in routine care are unavailable. METHODS: We identified patients with a primary diagnosis of lumbar stenosis who had fusion surgery in 2003 or 2004 (n = 16,822). We identified factors associated with BMP use: major medical complications during the index hospitalization, rates of rehospitalization within 30 days, and rates of reoperation within 4 years of follow-up (through 2008). RESULTS: Use of BMP increased rapidly, from 5.5% of fusion cases in 2003 to 28.1% of fusion cases in 2008. BMP use was greater among patients with previous surgery and among those having complex fusion procedures (combined anterior and posterior approach, or greater than 2 disc levels). Major medical complications, wound complications, and 30-day rehospitalization rates were nearly identical with or without BMP. Reoperation rates were also very similar, even after stratifying by previous surgery or surgical complexity, and after adjusting for demographic and clinical features. On average, adjusted hospital charges for operations involving BMP were about $15,000 more than hospital charges for fusions without BMP, though reimbursement under Medicare's Diagnosis-Related Group system averaged only about $850 more. Significantly fewer patients receiving BMP were discharged to a skilled nursing facility (15.9% vs. 19.0%, P < 0.001). CONCLUSION: In this older population having fusion surgery for lumbar stenosis, uptake of BMP was rapid, and greatest among patients with prior surgery or having complex fusion procedures. BMP appeared safe in the perioperative period, with no increase in major medical complications. Use of BMP was associated with greater hospital charges but fewer nursing home discharges, and was not associated with reduced likelihood of reoperation.

Dominici, M., et al. (2006). "Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement." Cytotherapy 8(4): 315-317.

The considerable therapeutic potential of human multipotent mesenchymal stromal cells (MSC) has generated markedly increasing interest in a wide variety of biomedical disciplines. However, investigators report studies of MSC using different methods of isolation and expansion, and different approaches to characterizing the cells. Thus it is increasingly difficult to compare and contrast study outcomes, which hinders progress in the field. To begin to address this issue, the Mesenchymal and Tissue Stem Cell Committee of the International Society for Cellular Therapy proposes minimal criteria to define human MSC. First, MSC must be plastic-adherent when maintained in standard culture conditions. Second, MSC must express CD105, CD73 and CD90, and lack expression of CD45, CD34, CD14 or CD11b, CD79alpha or CD19 and HLA-DR surface molecules. Third, MSC must differentiate to osteoblasts, adipocytes and chondroblasts in vitro. While these criteria will probably require modification as new knowledge unfolds, we believe this minimal set of standard criteria will foster a more uniform characterization of MSC and facilitate the exchange of data among investigators.

Dominici, M., et al. (2004). "Hematopoietic cells and osteoblasts are derived from a common marrow progenitor after bone marrow transplantation." Proc Natl Acad Sci U S A 101(32): 11761-11766.

Bone and bone marrow are closely aligned physiologic compartments, suggesting that these tissues may represent a single functional unit with a common bone marrow progenitor that gives rise to both osteoblasts and hematopoietic cells. Although reports of multilineage engraftment by a single marrow-derived stem cell support this idea, more recent evidence has challenged claims of stem cell transdifferentiation and therefore the existence of a multipotent hematopoietic/osteogenic progenitor cell. Using a repopulation assay in mice, we show here that gene-marked, transplantable marrow cells from the plastic-nonadherent population can generate both functional osteoblasts/osteocytes and hematopoietic cells. Fluorescent in situ hybridization for the X and Y chromosomes and karyotype analysis of cultured osteoblasts confirmed the donor origin of these cells and excluded their generation by a fusion process. Molecular analysis demonstrated a common retroviral integration site in clonogenic hematopoietic cells and osteoprogenitors from each of seven animals studied, establishing a shared clonal origin for these ostensibly independent cell types. Our findings indicate that the bone marrow contains a primitive cell able to generate both the hematopoietic and osteocytic lineages. Its isolation and characterization may suggest novel treatments for genetic bone diseases and bone injuries.

Dunac, A., et al. (2007). "Neurological and functional recovery in human stroke are associated with peripheral blood CD34+ cell mobilization." J Neurol 254(3): 327-332.

BACKGROUND: A spontaneous mobilization of Peripheral Blood-Mononuclear CD34+ Cells (PB-MNC-CD34+) has recently been reported in human myocardial infarction and found to be related to improved heart function and survival. However, nothing is known regarding a possible relation between PB-MNC-CD34+ mobilization and neurological recovery in human acute cerebral ischemia. METHODS AND RESULTS: PB-MNC-CD34+ were determined daily after an acute cerebral ischemic attack for 14 days in 25 patients with acute ischemic stroke and compared with controls. Results indicated that stroke was followed by large and bursting mobilizations of PB-MNC-CD34+. The amplitude of the mobilizations was similar to those observed in Granulocyte Colony Stimulating Factor (G-CSF) conditioned aplastic patients following myeloablative therapy before leukapheresis and autologous bone graft. The extent of PB-MNC-CD34+ mobilization in each patient was directly related to neurological and functional recoveries as assessed by NIH Stroke Scale, and modified Rankin Scale respectively. CONCLUSIONS: The mobilization of PB-MNC-CD34+ cells might be predictive of neurological and functional recovery.

Ebihara, Y., et al. (2006). "Hematopoietic origins of fibroblasts: II. In vitro studies of fibroblasts, CFU-F, and fibrocytes." Exp Hematol 34(2): 219-229.

OBJECTIVE: Using transplantation of a clonal population of cells derived from a single hematopoietic stem cell (HSC) of transgenic enhanced green fluorescent protein (EGFP) mice, we have documented the hematopoietic origin of myofibroblasts, such as kidney mesangial cells and brain microglial cells. Because myofibroblasts are thought to be an activated form of fibroblasts, we tested the hypothesis that fibroblasts are derived from HSCs. MATERIALS AND METHODS: Clones of cells derived from single cells of EGFP Ly-5.2 C57Bl/6 mice were transplanted into lethally irradiated Ly-5.1 mice. Using bone marrow and peripheral blood cells from mice showing high-level multilineage hematopoietic reconstitution, we induced growth of fibroblasts in vitro. RESULTS: Culture of EGFP(+) bone marrow cells from clonally engrafted mice revealed adherent cells with morphology typical of fibroblasts. Flow cytometric analysis revealed that the majority of these cells are CD45(-) and express collagen-I and the collagen receptor, discoidin domain receptor 2 (DDR2). Reverse transcriptase polymerase chain reaction analysis of cultured cells demonstrated expression of procollagen 1-alpha1, DDR2, fibronectin, and vimentin mRNA. Fibroblast colonies consisting of EGFP(+) cells were observed in cultures of bone marrow cells from clonally engrafted mice, indicating an HSC origin of fibroblast colony-forming units. Culture of peripheral blood nucleated cells from clonally engrafted mice revealed EGFP(+) cells expressing collagen-I and DDR2, indicating that fibrocytes are also derived from HSCs. CONCLUSION: We conclude that a population of fibroblasts and their precursors are derived from HSCs.

Edgar, C. and T. A. Einhorn (2011). "Treatment of avascular necrosis of the femoral head with drilling and injection of concentrated autologous bone marrow." Tech Orthop 26(1): 2-8.

El-Sharkawy, H., et al. (2007). "Platelet-rich plasma: growth factors and pro- and anti-inflammatory properties." J Periodontol 78(4): 661-669.

BACKGROUND: Platelet-rich plasma (PRP) promotes regeneration of bone, presumably through the action of concentrated growth factors. However, it is not clear how PRP affects the inflammatory response. The purpose of this study was to analyze the growth factors in PRP and to study the effects of PRP on monocyte cytokine release and lipoxin A(4) (LXA(4)) generation. METHODS: PRP was prepared from healthy donors. Platelet-derived growth factor (PDGF)-AB, PDGF-BB, transforming growth factor-beta1, insulin-like growth factor-I, fibroblast growth factor-basic (FGF-b), epidermal growth factor (EGF), vascular endothelial growth factor, interleukin-12 (p40/70), and regulated on activation, normal T-cell expressed and secreted (RANTES) levels were evaluated by enzyme-linked immunosorbent assay and bead-based multiplexing. Peripheral blood monocytes were isolated and cultured with or without PRP. Cytokine, chemokine, and LXA(4) levels as well as monocyte chemotactic migration were analyzed. RESULTS: Growth factors were increased significantly in PRP compared to whole blood (WB) and platelet-poor plasma. Monocyte chemotactic protein-1 (MCP-1) was suppressed significantly by PRP, whereas RANTES was increased significantly in monocyte cultures. LXA(4) levels were significantly higher in PRP compared to WB. PRP stimulated monocyte chemotaxis in a dose-dependent fashion, whereas RANTES, in part, was responsible for PRP-mediated monocyte migration. CONCLUSIONS: PRP is a rich source of growth factors and promoted significant changes in monocyte-mediated proinflammatory cytokine/chemokine release. LXA(4) was increased in PRP, suggesting that PRP may suppress cytokine release, limit inflammation, and, thereby, promote tissue regeneration.

Fan, Y., et al. (2008). "Interleukin-6 stimulates circulating blood-derived endothelial progenitor cell angiogenesis in vitro." J Cereb Blood Flow Metab 28(1): 90-98.

Circulating blood endothelial progenitor cells (EPCs) contribute to postnatal vasculogenesis, providing a novel therapeutic target for vascular diseases. However, the molecular mechanism of EPC-induced vasculogenesis is unknown. Interleukin-6 plays multiple functions in angiogenesis and vascular remodeling. Our previous study demonstrated that the polymorphism (174G>C) in IL-6 gene promoter was associated with brain vascular disease. In this study, we investigated if IL-6 receptor is expressed in human EPCs derived from circulating mononuclear cells, and if interleukin-6 (IL-6) stimulates EPC angiogenesis in vitro. First, we isolated and cultured mononuclear cells from adult human circulating blood. We obtained EPC clones that were further cultured and expended for the angiogenesis study. We found that the EPCs possessed human mature endothelial cell phenotypes; however, they proliferated much faster than mature endothelial cells (P<0.05). We then found that IL-6 receptor (gp-80) was expressed in the EPCs, and that administration of IL-6 could activate receptor gp80/gp130 signaling pathways including downstream extracellular signal-regulated kinase 1/2 and STAT3 phosphorylation in EPCs. Furthermore, IL-6 stimulated EPC proliferation, migration, and matrigel tube formation in a dose-dependent manner (P<0.05); anti-IL-6 antibodies or IL-6 receptor could abolish these effects (P<0.05). These results suggest that IL-6 plays a crucial role in the biologic behavior of blood-derived EPCs, which may help clarify the mechanism of IL-6 inflammatory-related diseases.

Fang, T. D., et al. (2005). "Angiogenesis is required for successful bone induction during distraction osteogenesis." J Bone Miner Res 20(7): 1114-1124.

The role of angiogenesis during mechanically induced bone formation is incompletely understood. The relationship between the mechanical environment, angiogenesis, and bone formation was determined in a rat distraction osteogenesis model. Disruption of either the mechanical environment or endothelial cell proliferation blocked angiogenesis and bone formation. This study further defines the role of the mechanical environment and angiogenesis during distraction osteogenesis. INTRODUCTION: Whereas successful fracture repair requires a coordinated and complex transcriptional program that integrates mechanotransductive signaling, angiogenesis, and osteogenesis, the interdependence of these processes is not fully understood. In this study, we use a system of bony regeneration known as mandibular distraction osteogenesis (DO) in which a controlled mechanical stimulus promotes bone induction after an osteotomy and gradual separation of the osteotomy edges to examine the relationship between the mechanical environment, angiogenesis, and osteogenesis. MATERIALS AND METHODS: Adult Sprague-Dawley rats were treated with gradual distraction, gradual distraction plus the angiogenic inhibitor TNP-470, or acute distraction (a model of failed bony regeneration). Animals were killed at the end of distraction (day 13) or at the end of consolidation (day 41) and examined with muCT, histology, and immunohistochemistry for angiogenesis and bone formation (n = 4 per time-point per group). An additional group of animals (n = 6 per time-point per group) was processed for microarray analysis at days 5, 9, 13, 21, and 41. RESULTS AND CONCLUSIONS: Either TNP-470 administration or disruption of the mechanical environment prevented normal osteogenesis and resulted in a fibrous nonunion. Subsequent analysis of the regenerate showed an absence of angiogenesis by gross histology and immunohistochemical localization of platelet endothelial cell adhesion molecule in the groups that failed to heal. Microarray analysis revealed distinct patterns of expression of genes associated with osteogenesis, angiogenesis, and hypoxia in each of the three groups. Our findings confirm the interdependence of the mechanical environment, angiogenesis, and osteogenesis during DO, and suggest that induction of proangiogenic genes and the proper mechanical environment are both necessary to support new vasculature for bone induction in DO.

Feng, T., et al. (2010). "Generation of mucosal dendritic cells from bone marrow reveals a critical role of retinoic acid." J Immunol 185(10): 5915-5925.

It is unknown how dendritic cells (DCs) become specialized as mucosal DCs and maintain intestinal homeostasis. We report that a subset of bone marrow cells freshly isolated from C57BL/6 mice express the retinoic acid (RA)-synthesizing enzyme aldehyde dehydrogenase family 1, subfamily A2 (ALDH1a2) and are capable of providing RA to DC precursors in the bone marrow microenvironment. RA induced bone marrow-derived DCs to express CCR9 and ALDH1a2 and conferred upon them mucosal DC functions, including induction of Foxp3(+) regulatory T cells, IgA-secreting B cells, and gut-homing molecules. This response of DCs to RA was dependent on a narrow time window and stringent dose effect. RA promoted bone marrow-derived DC production of bioactive TGF-beta by inhibiting suppressor of cytokine signaling 3 expression and thereby enhancing STAT3 activation. These RA effects were evident in vivo, in that mucosal DCs from vitamin A-deficient mice had reduced mucosal DC function, namely failure to induce Foxp3(+) regulatory T cells. Furthermore, MyD88 signaling enhanced RA-educated DC ALDH1a2 expression and was required for optimal TGF-beta production. These data indicate that RA plays a critical role in the generation of mucosal DCs from bone marrow and in their functional activity.

Feng, Y., et al. (2010). "Decreased in the number and function of circulation endothelial progenitor cells in patients with avascular necrosis of the femoral head." Bone 46(1): 32-40.

Fessel, J. (2013). "There are many potential medical therapies for atraumatic osteonecrosis." Rheumatology (Oxford) 52(2): 235-241.

Atraumatic osteonecrosis is a common complication of SLE and is seen in other connective tissue diseases, in patients treated with high doses of CSs, in HIV-infected patients and in alcoholic patients. Standard care is confined to analgesia, core decompression if the condition is early and affects the femoral head and joint replacement. However, consideration of the underlying biological mechanisms leads to the recognition of many potential therapies that might either prevent progression or, even, reverse the process if it is not yet too far advanced. These potential therapies merit detailed consideration. Critical points are that (i) histopathological evidence shows that the initial cellular event is apoptosis of osteocytes; and (ii) another requisite, as homeostasis requires that death and rebirth of osteocytes be balanced, is an accompanying inadequate proliferative capacity of osteoblasts. Thus, a logical approach to treatment includes measures that (i) reduce apoptosis of osteocytes and (ii) enhance proliferation of osteoblasts/pre-osteoblasts. Measures to reduce the ongoing apoptosis of osteocytes require reinforcing the effects of members of the Bcl-2 family (Bcl-2 itself and Mcl-1), the Wnt/catenin pathways (using an available sclerostin antibody) and HSPs (by application of local heat using US, deep wave diathermy or infrared), as well as administration of bisphosphonates and nitrates. Measures to enhance proliferation of osteoblasts/pre-osteoblasts include the use of stem cells, extracorporeal shock wave therapy, aspirin, the proteosome inhibitor bortezomib, melatonin and application of local heat. Use of VEGF would encourage proliferation of blood vessels and osteogenesis. Certain drugs that inhibit osteoblast proliferation should be avoided, including NSAIDs, serotonin reuptake inhibitors and thiazolidinediones.

Field, A. P. and R. Gillett (2010). "How to do a meta-analysis." Br J Math Stat Psychol 63(Pt 3): 665-694.

Meta-analysis is a statistical tool for estimating the mean and variance of underlying population effects from a collection of empirical studies addressing ostensibly the same research question. Meta-analysis has become an increasing popular and valuable tool in psychological research, and major review articles typically employ these methods. This article describes the process of conducting meta-analysis: selecting articles, developing inclusion criteria, calculating effect sizes, conducting the actual analysis (including information on how to do the analysis on popular computer packages such as IBM SPSS and R) and estimating the effects of publication bias. Guidance is also given on how to write up a meta-analysis.

Forbes, S. J., et al. (2002). "Adult stem cell plasticity: new pathways of tissue regeneration become visible." Clin Sci (Lond) 103(4): 355-369.

There has recently been a significant change in the way we think about organ regeneration. In the adult, organ formation and regeneration was thought to occur through the action of organ-or tissue-restricted stem cells (i.e. haematopoietic stem cells making blood; gut stem cells making gut, etc.). However, there is a large body of recent work that has extended this model. Thanks to lineage tracking techniques, we now believe that stem cells from one organ system, for example the haematopoietic compartment, can develop into the differentiated cells within another organ system, such as liver, brain or kidney. This cellular plasticity not only occurs under experimental conditions, but has also been shown to take place in humans following bone marrow and organ transplants. This trafficking is potentially bi-directional, and even differentiated cells from different organ systems can interchange, with pancreatic cells able to form hepatocytes, for example. In this review we will detail some of these findings and attempt to explain their biological significance.

Fortier, L. A., et al. (2010). "Concentrated bone marrow aspirate improves full-thickness cartilage repair compared with microfracture in the equine model." J Bone Joint Surg Am 92(10): 1927-1937.

BACKGROUND: The purpose of this study was to compare the outcomes of treatment with bone marrow aspirate concentrate, a simple, one-step, autogenous, and arthroscopically applicable method, with the outcomes of microfracture with regard to the repair of full-thickness cartilage defects in an equine model. METHODS: Extensive (15-mm-diameter) full-thickness cartilage defects were created on the lateral trochlear ridge of the femur in twelve horses. Bone marrow was aspirated from the sternum and centrifuged to generate the bone marrow concentrate. The defects were treated with bone marrow concentrate and microfracture or with microfracture alone. Second-look arthroscopy was performed at three months, and the horses were killed at eight months. Repair was assessed with use of macroscopic and histological scoring systems as well as with quantitative magnetic resonance imaging. RESULTS: No adverse reactions due to the microfracture or the bone marrow concentrate were observed. At eight months, macroscopic scores (mean and standard error of the mean, 9.4 + or - 1.2 compared with 4.4 + or - 1.2; p = 0.009) and histological scores (11.1 + or - 1.6 compared with 6.4 + or - 1.2; p = 0.02) indicated improvement in the repair tissue in the bone marrow concentrate group compared with that in the microfracture group. All scoring systems and magnetic resonance imaging data indicated that delivery of the bone marrow concentrate resulted in increased fill of the defects and improved integration of repair tissue into surrounding normal cartilage. In addition, there was greater type-II collagen content and improved orientation of the collagen as well as significantly more glycosaminoglycan in the bone marrow concentrate-treated defects than in the microfracture-treated defects. CONCLUSIONS: Delivery of bone marrow concentrate can result in healing of acute full-thickness cartilage defects that is superior to that after microfracture alone in an equine model. CLINICAL RELEVANCE: Delivery of bone marrow concentrate to cartilage defects has the clinical potential to improve cartilage healing, providing a simple, cost-effective, arthroscopically applicable, and clinically effective approach for cartilage repair.

Foster, T. E., et al. (2009). "Platelet-rich plasma: from basic science to clinical applications." Am J Sports Med 37(11): 2259-2272.

Platelet-rich plasma (PRP) has been utilized in surgery for 2 decades; there has been a recent interest in the use of PRP for the treatment of sports-related injuries. PRP contains growth factors and bioactive proteins that influence the healing of tendon, ligament, muscle, and bone. This article examines the basic science of PRP, and it describes the current clinical applications in sports medicine. This study reviews and evaluates the human studies that have been published in the orthopaedic surgery and sports medicine literature. The use of PRP in amateur and professional sports is reviewed, and the regulation of PRP by antidoping agencies is discussed.

Friedenstein, A. (1989). "Stromal-hematopoietic interrelationships: Maximov's ideas and modern models." Haematol Blood Transfus 32: 159-167.

Friedenstein, A. J., et al. (1970). "The development of fibroblast colonies in monolayer cultures of guinea-pig bone marrow and spleen cells." Cell Tissue Kinet 3(4): 393-403.

Friedenstein, A. J., et al. (1966). "Osteogenesis in transplants of bone marrow cells." J Embryol Exp Morphol 16(3): 381-390.

Galie, M., et al. (2008). "Comparison of different centrifugation protocols for the best yield of adipose-derived stromal cells from lipoaspirates." Plast Reconstr Surg 122(6): 233e-234e.

Gan, Y., et al. (2008). "The clinical use of enriched bone marrow stem cells combined with porous beta-tricalcium phosphate in posterior spinal fusion." Biomaterials 29(29): 3973-3982.

Cytotherapy for bone regeneration has not been widely used clinically. A new method based on enriched bone-marrow-derived mesenchymal stem cells (MSCs) combined with porous beta-tricalcium phosphate (beta-TCP) was used for posterior spinal fusion in 41 patients. The aim of the present study was to assess the clinical feasibility of peri-operative bone marrow stem cell enrichment and their combination with tricalcium phosphate. About 252 ml marrow per patient was harvested from bilateral iliac crest, the enriched MSCs were produced by a cell processor peri-operatively, then combined with porous beta-TCP granules by a negative pressure and a short-time incubation in the meantime of conventional operation, which were finally implanted back into the patient. About 45 ml enriched MSC suspension was collected, and 78+/-16% of MSCs were recovered. By enrichment technique, the number of colony-forming units which expressed alkaline phosphatase (CFUs-ALP+, to estimate the prevalence of MSCs) was increased 4.3 times; the increasing folds of bone marrow nucleated cells (NCs) and MSCs had a positive correlation. The natural log (ln) of MSC number declined with age, and also, the MSC number of younger subjects (< or =40 years) was more than that of older ones (>40 years), but none for NCs. The number of NCs and MSCs was not different significantly between men and women. However, the patients with thoracolumbar fracture (TLF) had significantly more MSCs than those with degenerative disc disease (DDD), but not for NCs. On the other hand, enriched MSCs could adhere to the wall of porous beta-TCP within 2h combination, and proliferate well during culture in vitro. After 34.5 months, 95.1% cases had good spinal fusion results. None of the samples before grafting was positive in bacterial culture. Only four patients had a little exudation or moderate swelling in their wounds, and recovered with conservative treatment.

Gangji, V., et al. (2011). "Autologous bone marrow cell implantation in the treatment of non-traumatic osteonecrosis of the femoral head: Five year follow-up of a prospective controlled study." Bone 49(5): 1005-1009.

OBJECTIVE: To determine the efficacy of bone marrow cell implantation into the necrotic lesion of the femoral head on clinical symptoms and the progression of osteonecrosis of the femoral head in comparison with core decompression. METHODS: We studied nineteen patients and twenty four hips with early stage osteonecrosis of the femoral head. The hips were allocated to either core decompression only or core decompression and implantation of bone marrow cells. Both patients and assessors were blind with respect to treatment group assignment. The primary outcomes were clinical symptoms and disease progression. RESULTS: Bone marrow implantation afforded a significant reduction in pain and in joint symptoms and reduced the incidence of fractural stages. At 60 months, eight of the eleven hips in the control group had deteriorated to the fractural stage whereas only three of the thirteen hips in the bone marrow graft group had progressed to that stage. Survival analysis showed a significant difference in the time to failure between the two groups at 60 months. Patients had only minor side-effects after the treatments. CONCLUSIONS: This long term follow-up study confirmed that implantation of autologous bone marrow cells in the necrotic lesion might be an effective treatment for patients with early stages of osteonecrosis of the femoral head.

Gangji, V. and J. P. Hauzeur (2005). "Treatment of osteonecrosis of the femoral head with implantation of autologous bone-marrow cells. Surgical technique." J Bone Joint Surg Am 87 Suppl 1(Pt 1): 106-112.

BACKGROUND: Aseptic nontraumatic osteonecrosis of the femoral head is a disorder that can lead to femoral head collapse and the need for total hip replacement. Since osteonecrosis may be a disease of mesenchymal cells or bone cells, the possibility has been raised that bone marrow containing osteogenic precursors implanted into a necrotic lesion of the femoral head may be of benefit in the treatment of this condition. For this reason, we studied the implantation of autologous bone-marrow mononuclear cells in a necrotic lesion of the femoral head to determine the effect on the clinical symptoms and the stage and volume of osteonecrosis. METHODS: We studied thirteen patients (eighteen hips) with stage-I or II osteonecrosis of the femoral head, according to the system of the Association Research Circulation Osseous. The hips were allocated to a program of either core decompression (the control group) or core decompression and implantation of autologous bone-marrow mononuclear cells (the bone-marrow-graft group). Both patients and assessors were blind with respect to treatment-group assignment. The primary outcomes studied were safety, clinical symptoms, and disease progression. RESULTS: After twenty-four months, there was a significant reduction in pain (p = 0.021) and in joint symptoms measured with the Lequesne index (p = 0.001) and the WOMAC index (p = 0.013) within the bone-marrow-graft group. At twenty-four months, five of the eight hips in the control group had deteriorated to stage III, whereas only one of the ten hips in the bone-marrow-graft group had progressed to this stage. Survival analysis showed a significant difference in the time to collapse between the two groups (p = 0.016). Implantation of bone-marrow mononuclear cells was associated with only minor side effects. CONCLUSIONS: Implantation of autologous bone-marrow mononuclear cells appears to be a safe and effective treatment for early stages of osteonecrosis of the femoral head. Although the findings of this study are promising, their interpretation is limited because of the small number of patients and the short duration of follow-up. Further study is needed to confirm the results.

Gangji, V. and J. P. Hauzeur (2009). "Cellular-based therapy for osteonecrosis." Orthop Clin North Am 40(2): 213-221.

This review article describes bone remodeling in the context of osteonecrosis as a bone disease, the use of stem cells in bone and vascular diseases, and cellular therapy in osteonecrosis.

Gangji, V., et al. (2004). "Treatment of osteonecrosis of the femoral head with implantation of autologous bone-marrow cells. A pilot study." J Bone Joint Surg Am 86-A(6): 1153-1160.

Gangji, V., et al. (2003). "Abnormalities in the replicative capacity of osteoblastic cells in the proximal femur of patients with osteonecrosis of the femoral head." J Rheumatol 30(2): 348-351.

OBJECTIVE: Aseptic nontraumatic osteonecrosis (ON) of the femoral head is a painful disorder that often leads to femoral head collapse due to subchondral fracture. We postulated that alteration of osteoblast function might play a role in the pathophysiology of ON. We evaluated the ex vivo proliferation rate and differentiation capacity of osteoblasts derived from the intertrochanteric region of the femur and of the iliac crest of patients with ON of the femoral head and compared it with patients with hip osteoarthritis (OA). METHODS: We examined the function of osteoblastic cells in cultures derived from bone biopsies of the intertrochanteric region of the femur and of the iliac crest obtained from 13 patients with ON of the femoral head and 8 patients with hip OA. The replicative capacity was assessed by the proliferation rate in secondary culture. The phenotypic characterization was evaluated by the level of alkaline phosphatase activity, the sensitivity to 1,25 (OH)2 vitamin D3, and collagen synthesis. RESULTS: The replicative capacity of the osteoblastic cells of the intertrochanteric area of the femur in ON patients was significantly reduced compared to patients with OA. The capacity of differentiation, however, was not different between ON and OA patients. CONCLUSION: The replicative capacity of osteoblastic cells is significantly reduced in the femur of patients with ON. Our results confirm that altered osteoblastic function plays a role in the pathophysiology of ON of the femoral head.

Gao, D., et al. (2009). "Bone marrow-derived endothelial progenitor cells contribute to the angiogenic switch in tumor growth and metastatic progression." Biochim Biophys Acta 1796(1): 33-40.

Emerging evidence indicates that bone marrow (BM)-derived endothelial progenitor cells (EPCs) contribute to angiogenesis-mediated growth of certain tumors in mice and human. EPCs regulate the angiogenic switch via paracrine secretion of proangiogenic growth factors and by direct luminal incorporation into sprouting nascent vessels. While the contributions of EPCs to neovessel formation in spontaneous and transplanted tumors and to the metastatic transition have been reported to be relatively low, remarkably, specific EPC ablation in vivo has resulted in severe angiogenesis inhibition and impaired primary and metastatic tumor growth. The existence of a BM reservoir of EPCs, and the selective involvement of EPCs in neovascularization, have attracted considerable interest because these cells represent novel target for therapeutic intervention. In addition, EPCs are also being used as pharmacodynamic surrogate markers for monitoring cancer progression, as well as for optimizing efficacy of anti-angiogenic therapies in the clinic. This review will focus primarily on recent advances and emerging concepts in the field of EPC biology and discuss ongoing debates involving the role of EPCs in tumor neovascularization. For detailed information on the in vitro characterization of EPCs contribution to non-tumor pathologies, the reader is directed towards several excellent reviews and publications [F. Bertolini, Y. Shaked, P. Mancuso and R.S. Kerbel, Nat. Rev., Cancer 6 (2006) 835-845. [1]] [J.M. Hill, T. Finkel and A.A. Quyyumi, Vox Sang. 87 Suppl 2 (2004) 31-37. [2]] [A.Y. Khakoo and T. Finkel, Annu. Rev. Med. 56 (2005) 79-101. [3]] [H.G. Kopp, C.A. Ramos and S. Rafii, Curr. Opin. Hematol. 13 (2006) 175-181. [4]; K.K. Hirschi, D.A. Ingram and M.C. Yoder, Arterioscler. Thromb. Vasc. Biol. 28 (2008) 1584-1595. [5]; F. Timmermans, J. Plum, M.C. Yoder, D.A. Ingram, B. Vandekerckhove and J. Case, J. Cell. Mol. Med. 13 (2009) 87-102. [6]] and reviews by Bertolini, Voest and Yoder in this issue.

Gao, Y. S. and C. Q. Zhang (2010). "Cytotherapy of osteonecrosis of the femoral head: a mini review." Int Orthop 34(6): 779-782.

The pathogenesis and aetiology of nontraumatic osteonecrosis of the femoral head has not been revealed completely. However, with advances in stem cell research and regenerative medicine, it is believed that the onset of osteonecrosis of the femoral head probably has a cellular origin, and the possible therapy of osteonecrosis of the femoral head based on cytotherapy has great potential. In this review, the aetiology of osteonecrosis of the femoral head, animal experiments and clinical applications of cytotherapy are summarized and analysed. Current problems and future challenges are discussed.

Giusti, I., et al. (2009). "Identification of an optimal concentration of platelet gel for promoting angiogenesis in human endothelial cells." Transfusion 49(4): 771-778.

BACKGROUND: Numerous studies have supported the use of topical blood components to improve wound healing and tissue regeneration. Platelet gel (PG), a hemocomponent obtained from mix of activated platelets (PLTs) and cryoprecipitate, is currently being used clinically in an attempt to improve tissue healing. The present study sought to define the most effective PG concentration to promote angiogenesis in vitro. STUDY DESIGN AND METHODS: The effects of PG-released supernatant at different concentrations on human endothelial cells were studied using different in vitro assays (proliferation, migration, invasion, cord formation, and wound healing). RESULTS: The concentration of PG-released supernatant had a significant influence on the angiogenic potential of endothelial cells. The optimal concentration for the stimulation of angiogenesis was 1.5 x 10(6) PLTs per microL in most of the in vitro experiments used in this study. Lower or higher concentrations of PG displayed a lower angiogenic potential. CONCLUSION: An optimal concentration of PG to promote angiogenesis in human endothelial cells was identified. Excessively high PG concentrations may inhibit the angiogenic process, thereby being counterproductive for wound healing in a clinical setting.

Glassman, S. D., et al. (2007). "Posterolateral lumbar spine fusion with INFUSE bone graft." Spine J 7(1): 44-49.

BACKGROUND CONTEXT: INFUSE has been proven effective in conjunction with threaded cages and bone dowels for single-level anterior lumbar interbody fusion (ALIF). The published experience with posterolateral fusion, although encouraging, utilizes a significantly higher dose and concentration of recombinant human bone morphogenic protein-2 (rhBMP-2) and a different carrier than the commercially available INFUSE. PURPOSE: To present an assessment of fusion rate for posterolateral spine fusion with INFUSE Bone Graft. STUDY DESIGN/SETTING: Retrospective review of patients treated using INFUSE in posterolateral spine fusion in a single institution. PATIENT SAMPLE: 91 patients with minimum 2-year follow-up who underwent posterolateral spine fusion using INFUSE as an iliac crest bone graft (ICBG) substitute. OUTCOME MEASURES: Fusion rate based on fine-cut computed tomographic (CT) scans with sagittal and coronal reconstructions. METHODS: Fusion was performed using one large INFUSE kit (12 mg rhBMP-2, 1.5 mg/mL), which was prepared according to the manufacturer's instructions. The INFUSE sponge was wrapped around the local bone or graft extender and placed over the decorticated surfaces in the lateral gutters. Postoperative CT scans with reconstructions were reviewed by two independent orthopedic spine surgeons. CT scans of a comparison group of 35 patients who underwent primary single-level posterolateral fusion with ICBG were also reviewed. RESULTS: The overall group had a mean 4.38 CT fusion grade and a 6.6% nonunion rate. Primary one-level fusion cases (n=48) had a mean 4.42 fusion grade a 4.2% nonunion rate. Primary multilevel fusions (n=27) had a mean 4.65 CT grade and no nonunions detected. Assessment of the 35 primary one-level ICBG control cases demonstrated a mean CT grade of 4.35 and a nonunion rate of 11.4%. In the 16 cases of revision for prior nonunion, mean CT grade was 3.81 and 4 subjects had nonunions. Additional subgroup analysis showed that smokers (n=14) had a mean 4.32 CT grade with no nonunions. Men had a mean 4.04 CT grade and an 11.1% nonunion rate compared with a mean 4.61 CT grade and 3.6% nonunion rate in women. This difference was statistically significant (p=.036). No significant differences in fusion rate were observed based upon the specific graft extender used (p=.200). CONCLUSIONS: Posterolateral spine fusion involves a more difficult healing environment with a limited surface for healing, a gap between transverse processes and the milieu of distractive forces. Historically, only ICBG has been able to overcome these challenges and reliably generate a successful posterolateral lumbar spine fusion. In contrast to prior studies, clinically available INFUSE delivers only 12 mg rhBMP-2 at a concentration of 1.5 mg/mL. Despite the lower dose and concentration of rhBMP-2, this study suggests that fusion success with INFUSE is equivalent to ICBG for posterolateral spine fusion. As with ICBG, development of solid fusion or nonunion is a multifactorial process. The use of INFUSE is not a substitute for proper surgical technique or optimization of patient-related risk factors. Additional studies are needed to determine the incremental benefit of a greater rhBMP-2 dose or use of alternative carriers for posterolateral fusion. Finally, correlation between radiographic findings and clinical outcomes, and a cost-benefit analysis are needed. Despite these issues, this study presents compelling evidence that commercially available INFUSE is an effective ICBG substitute for one- and two-level posterolateral instrumented spine fusion.

Gobbi, A., et al. (2011). "One-step cartilage repair with bone marrow aspirate concentrated cells and collagen matrix in full-thickness knee cartilage lesions: Results at 2 year follow up." Cartilage 2: 286-299.

Objective: The purpose of our study was to determine the effectiveness of cartilage repair utilizing 1-step surgery with bone marrow aspirate concentrate (BMAC) and a collagen I/III matrix (Chondro-Gide, Geistlich, Wolhusen, Switzerland). Materials and Methods: We prospectively followed up for 2 years 15 patients (mean age, 48 years) who were operated for grade IV cartilage lesions of the knee. Six of the patients had multiple chondral lesions; the average size of the lesions was 9.2 cm2. All patients underwent a mini-arthrotomy and concomitant transplantation with BMAC covered with the collagen matrix. Coexisting pathologies were treated before or during the same surgery. X-rays and MRI were collected preoperatively and at 1 and 2 years’ follow-up. Visual analog scale (VAS), International Knee Documentation Committee (IKDC), Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm, Marx, SF-36 (physical/mental), and Tegner scores were collected preoperatively and at 6, 12, and 24 months’ follow-up. Four patients gave their consent for second-look arthroscopy and 3 of them for a concomitant biopsy. Results: Patients showed significant improvement in all scores at final follow-up (P < 0.005). Patients presenting single lesions and patients with small lesions showed higher improvement. MRI showed coverage of the lesion with hyaline-like tissue in all patients in accordance with clinical results. Hyaline-like histological findings were also reported for all the specimens analyzed. No adverse reactions or postoperative complications were noted. Conclusion: This study showed that 1-step surgery with BMAC and collagen I/III matrix could be a viable technique in the treatment of grade IV knee chondral lesions.

Golubev, A. (2012). "Genes at work in random bouts: stochastically discontinuous gene activity makes cell cycle duration and cell fate decisions variable, thus providing for stem cells plasticity." Bioessays 34(4): 311-319.

Cell interdivision periods (IDP) in homogenous cell populations vary stochastically. Another aspect of probabilistic cell behavior is randomness in cell differentiation. These features are suggested to result from competing stochastic events of assembly/disassembly of the transcription pre-initiation complex (PIC) at gene promoters. The time needed to assemble a proper PIC from different proteins, which must be numerous enough to make their combination gene specific, may be comparable to the IDP. Nascent mRNA visualization at defined genes and inferences from protein level fluctuations in single cells suggest that some genes do operate in this way. The onset of mRNA production by such genes may miss the time windows provided by the cell cycle, resulting in cells differentiating into those in which the respective mRNAs are either present or absent. This creates a way to generate cell phenotype diversity in multicellular organisms.

Gomperts, B. N., et al. (2006). "Circulating progenitor epithelial cells traffic via CXCR4/CXCL12 in response to airway injury." J Immunol 176(3): 1916-1927.

Recipient airway epithelial cells are found in human sex-mismatched lung transplants, implying that circulating progenitor epithelial cells contribute to the repair of the airway epithelium. Markers of circulating progenitor epithelial cells and mechanisms for their trafficking remain to be elucidated. We demonstrate that a population of progenitor epithelial cells exists in the bone marrow and the circulation of mice that is positive for the early epithelial marker cytokeratin 5 (CK5) and the chemokine receptor CXCR4. We used a mouse model of sex-mismatched tracheal transplantation and found that CK5+ circulating progenitor epithelial cells contribute to re-epithelialization of the airway and re-establishment of the pseudostratified epithelium. The presence of CXCL12 in tracheal transplants provided a mechanism for CXCR4+ circulating progenitor epithelial cell recruitment to the airway. Depletion of CXCL12 resulted in the epithelium defaulting to squamous metaplasia, which was derived solely from the resident tissue progenitor epithelial cells. Our findings demonstrate that CK5+CXCR4+ cells are markers of circulating progenitor epithelial cells in the bone marrow and circulation and that CXCR4/CXCL12-mediated recruitment of circulating progenitor epithelial cells is necessary for the re-establishment of a normal pseudostratified epithelium after airway injury. These findings support a novel paradigm for the development of squamous metaplasia of the airway epithelium and for developing therapeutic strategies for circulating progenitor epithelial cells in airway diseases.

Goujon, E. (1869). "Researches experimentals sur les proprietes phsiologigues de al moelle des os." Journal de l'Anatomie et de Physiologie Normales et Pathologiques de l'Homme et des Animaux 6: 399.

Graf, T. (2002). "Differentiation plasticity of hematopoietic cells." Blood 99(9): 3089-3101.

Grcevic, D., et al. (2012). "In vivo fate mapping identifies mesenchymal progenitor cells." Stem Cells 30(2): 187-196.

Adult mesenchymal progenitor cells have enormous potential for use in regenerative medicine. However, the true identity of the progenitors in vivo and their progeny has not been precisely defined. We hypothesize that cells expressing a smooth muscle alpha-actin promoter (alphaSMA)-directed Cre transgene represent mesenchymal progenitors of adult bone tissue. By combining complementary colors in combination with transgenes activating at mature stages of the lineage, we characterized the phenotype and confirmed the ability of isolated alphaSMA(+) cells to progress from a progenitor to fully mature state. In vivo lineage tracing experiments using a new bone formation model confirmed the osteogenic phenotype of alphaSMA(+) cells. In vitro analysis of the in vivo-labeled SMA9(+) cells supported their differentiation potential into mesenchymal lineages. Using a fracture-healing model, alphaSMA9(+) cells served as a pool of fibrocartilage and skeletal progenitors. Confirmation of the transition of alphaSMA9(+) progenitor cells to mature osteoblasts during fracture healing was assessed by activation of bone-specific Col2.3emd transgene. Our findings provide a novel in vivo identification of defined population of mesenchymal progenitor cells with active role in bone remodeling and regeneration. STEM CELLS 2012; 30:187-196.

Grove, J. E., et al. (2004). "Plasticity of bone marrow-derived stem cells." Stem Cells 22(4): 487-500.

Stem cell plasticity refers to the ability of adult stem cells to acquire mature phenotypes that are different from their tissue of origin. Adult bone marrow cells (BMCs) include two populations of bone marrow stem cells (BMCs): hematopoietic stem cells (HSCs), which give rise to all mature lineages of blood, and mesenchymal stem cells (MSCs), which can differentiate into bone, cartilage, and fat. In this article, we review the literature that lends credibility to the theory that highly plastic BMCs have a role in maintenance and repair of nonhematopoietic tissue. We discuss the possible mechanisms by which this may occur. Also reviewed is the possibility that adult BMCs can change their gene expression profile after fusion with a mature cell, which has brought into question whether this stem cell plasticity is real.

Haid, R. W., Jr., et al. (2004). "Posterior lumbar interbody fusion using recombinant human bone morphogenetic protein type 2 with cylindrical interbody cages." Spine J 4(5): 527-538; discussion 538-529.

BACKGROUND CONTEXT: In a large series of human patients undergoing open anterior lumbar interbody fusion with a tapered titanium fusion cage, recombinant human bone morphogenetic protein type 2 (rhBMP-2) on an absorbable collagen sponge carrier has been shown to decrease operative time and blood loss, to promote osteoinduction and fusion and to be a safe and effective substitute for iliac crest harvesting. PURPOSE: The purpose of the study was to determine the clinical and radiographic outcomes in patients treated for single-level degenerative lumbar disc disease with a posterior interbody fusion, using stand-alone cylindrical threaded titanium fusion cages with either autogenous bone graft or rhBMP-2 and an absorbable collagen sponge carrier. STUDY DESIGN/SETTING: A prospective, randomized, nonblinded, 2-year pilot study at 14 investigational sites. PATIENT SAMPLE: Between March 1999 and December 1999, 67 patients with symptomatic, single-level degenerative lumbar disc disease of at least 6 months' duration underwent a single-level posterior lumbar interbody fusion using two paired cylindrical threaded titanium fusion devices. Patients were randomly assigned to one of two groups: one (n=34 patients) received rhBMP-2 on a collagen sponge carrier; the other (n=33 patients) autogenous iliac crest bone graft. OUTCOME MEASURES: Clinical outcomes were measured using low back and leg pain numerical rating scales, the Short Form (SF)-36, Oswestry Low Back Pain Disability Questionnaire and work status. Plain radiographs and computed tomographic scans were used to evaluate fusion at 6, 12 and 24 months after surgery. METHODS: In this prospective nonblinded study, 67 patients were randomly assigned to one of two groups who underwent interbody fusion using two cylindrical threaded fusion cages: the investigational group (34 patients), who received rhBMP-2 on an absorbable collagen sponge, and a control group (33 patients), who received autogenous iliac crest bone graft. Clinical data were collected and analyzed by a commercial entity. RESULTS: The mean operative time and blood loss for the investigational rhBMP-2 group was 2.6 hours and 322.8 ml, respectively. For the autograft control group, these values were 3.0 hours and 372.7 ml. The differences were not significant. Although not statistically different, at 24 months, the investigational group's fusion rate of 92.3% was higher than the control's at 77.8%. At all postoperative intervals, the mean Oswestry, back and leg pain scores and physical components of the SF-36 improved in both treatment groups compared with preoperative scores, but no significant differences were found between groups. A statistically significant difference in the change in back pain was found at 24 months for the investigational group. In the control group, two adverse events related to harvesting of the iliac crest graft occurred in two patients (6.1%). CONCLUSIONS: This small multicenter, randomized, nonblinded trial showed few statistically significant differences between the study groups. Both groups showed comparable improvements on outcome scores. Overall results show that the use of rhBMP-2 can eliminate the need for harvesting iliac crest graft and may be an equivalent replacement for autograft for use in successful posterior lumbar interbody fusions. Further studies of the use of rhBMP-2 in posterior lumbar interbody fusion cage procedures are needed.

Haywood, L., et al. (2003). "Inflammation and angiogenesis in osteoarthritis." Arthritis Rheum 48(8): 2173-2177.

OBJECTIVE: To quantify the relationship between inflammation and angiogenesis in synovial tissue from patients with osteoarthritis (OA). METHODS: Hematoxylin and eosin staining and histologic grading for inflammation were performed for 104 patients who met the American College of Rheumatology criteria for OA and had undergone total joint replacement or arthroscopy. A purposive sample of synovial specimens obtained from 70 patients was used for further analysis. Vascular endothelium, endothelial cell (EC) proliferating nuclei, macrophages, and vascular endothelial growth factor (VEGF) were detected by immunohistochemical analysis. Angiogenesis (EC proliferation, EC fractional area), macrophage fractional area, and VEGF immunoreactivity were measured using computer-assisted image analysis. Double immunofluorescence histochemical analysis was used to determine the cellular localization of VEGF. Radiographic scores for joint space narrowing and osteophyte formation in the knee were also assessed. RESULTS: Synovial tissue samples from 32 (31%) of 104 patients with OA showed severe inflammation; thickened intimal lining and associated lymphoid aggregates were often observed. The EC fractional area, EC proliferation, and VEGF immunoreactivity all increased with increasing histologic inflammation grade and increasing macrophage fractional area. In the synovial intimal lining, VEGF immunoreactivity was localized to macrophages and increased with increasing EC fractional area and angiogenesis. No inflammation or angiogenic indices were significantly correlated with radiographic scores. CONCLUSION: Inflammation and angiogenesis in the synovium are associated with OA. The angiogenic growth factor VEGF generated by the inflamed synovium may promote angiogenesis, thereby contributing to inflammation in OA.

Hegde, V., et al. (2014). "A prospective comparison of 3 approved systems for autologous bone marrow concentration demonstrated nonequivalency in progenitor cell number and concentration." J Orthop Trauma 28(10): 591-598.

OBJECTIVES: To evaluate the efficacy of 3 commercially available systems: the Harvest SmartPReP 2 BMAC, Biomet BioCUE, and Arteriocyte Magellan systems. We compared the number and concentration of progenitor cells achieved both before and after centrifugation and the percentage of progenitor cells salvaged after centrifugation. METHODS: Forty patients, mean age 47 +/- 18 years (range: 18-92 years, 19 male/21 female) were prospectively consented for bilateral iliac crest aspiration. The first 20 aspirations compared the Harvest and Biomet systems, and based on those results, the second 20 compared the Harvest and Arteriocyte systems. One system was randomly assigned to each iliac crest. Each system's unique marrow acquisition process and centrifugation mechanism was followed. Samples for analysis were taken both immediately before the marrow was put into the centrifugation system (after acquisition), and after centrifugation. The number of progenitor cells in each sample was estimated by counting the connective tissue progenitors (CTPs). RESULTS: The Harvest system achieved a significantly greater number and concentration of CTPs both before and after centrifugation when compared to the Biomet system. There was no difference in the percent yield of CTPs after centrifugation. There was no significant difference in the number and concentration of CTPs between the Harvest and Arteriocyte systems before centrifugation, but the Harvest system had a significantly greater number and concentration of CTPs after centrifugation. The Harvest system also had a significantly higher percent yield of CTPs after centrifugation compared with the Arteriocyte system. CONCLUSIONS: The Harvest system resulted in a greater CTP number and concentration after centrifugation when compared with the Biomet and Arteriocyte systems and may thus provide increased osteogenic and chondrogenic capacity.

Hendrich, C., et al. (2009). "Safety of autologous bone marrow aspiration concentrate transplantation: Initial experieinces in 101 patients." Orthop Rev 1(e32): 99-103.

Hermann, P. C., et al. (2008). "Concentration of bone marrow total nucleated cells by a point-of-care device provides a high yield and preserves their functional activity." Cell Transplant 16(10): 1059-1069.

Stem and progenitor cell therapy is a novel strategy to enhance cardiovascular regeneration. Cell isolation procedures are crucial for the functional activity of the administered cellular product. Therefore, new isolation techniques have to be evaluated in comparison to the Ficoll isolation procedure as the current gold standard. Here we prospectively evaluated a novel point-of-care device (Harvest BMAC System) for the concentration of bone marrow total nucleated cells (TNC) in comparison to the Ficoll isolation procedure for bone marrow mononucleated cells (MNC). The yield in total numbers of TNC was 2.4-fold higher for Harvest compared to Ficoll. Despite significant differences in their cellular compositions, the colony-forming capacity was similar for both products. Intriguingly, the migratory capacity was significantly higher for the Harvest TNC (164 +/- 66%; p = 0.007). In a mouse model of hind limb ischemia, the increase in blood flow recovery was similar between Harvest BM-TNC and Ficoll BM-MNC (0.53 +/- 0.20 vs. 0.46 +/- 0.15; p = 0.88). However, adjustment of the injected cell number based on the higher yield of Harvest TNC resulted in a significant better recovery (0.64 +/- 0.16 vs. 0.46 +/- 0.15; p = 0.003). Cells concentrated by the Harvest point-of-care device show similar or greater functional activity compared to Ficoll isolation. However, the greater yield of cells and the wider range of cell types for the Harvest device may translate into an even greater therapeutic effect.

Hernandez-Gil, I. F., et al. (2006). "Physiological bases of bone regeneration II. The remodeling process." Medicina Oral S. L. 11: E151-e157.

Hernigou, P. and F. Beaujean (2002). "Treatment of osteonecrosis with autologous bone marrow grafting." Clin Orthop Relat Res(405): 14-23.

Core decompression with bone graft is used frequently in the treatment of osteonecrosis of the femoral head. Many different techniques have been described. In the current series, grafting was done with autologous bone marrow obtained from the iliac crest of patients operated on for osteonecrosis of the hip. The results of a prospective study of 189 hips in 116 patients treated with core decompression and autologous bone marrow grafting are reported. Patients were followed up from 5 to 10 years. The outcome was determined by the changes in the Harris hip score, by progression in radiographic stages, and by the need for hip replacement. The bone marrow was harvested with the patient under general anesthesia. The usual sites were the anterior iliac crests. The aspirated marrow was reduced in volume by concentration and injected into the femoral head after core decompression with a small trocar. When patients were operated on before collapse (Stage I and Stage II), hip replacement was done in nine of the 145 hips. Total hip replacement was necessary in 25 hips among the 44 hips operated on after collapse (Stage III and Stage IV). To measure the number of progenitor cells transplanted, the fibroblast colony forming unit was used as an indicator of the stroma cell activity. Patients who had the greater number of progenitor cells transplanted in their hips had better outcomes.

Hernigou, P., et al. (2008). "Percutaneous implantation of autologous bone marrow osteoprogenitor cells as treatment of bone avascular necrosis related to sickle cell disease." Open Orthop J 2: 62-65.

The treatment of bone a vascular necrosis is a big challenge considering the youthfulness of the patients involved by necrosis in sickle cell disease and the importance of the generated disability. A vascular osteonecrosis is an epiphysis pathology which could be treated by joint replacement with success, however, multiple surgical procedures are mostly necessary during the patient's life with a hazardous long term functional results. The treatment by autologous bone marrow grafting is an effective alternative which preserve the native joint. Using this mini-invasive high technology surgical treatment in early stages, a joint replacement could be avoided in many patients.

Hernigou, P., et al. (2006). "Percutaneous autologous bone-marrow grafting for nonunions. Surgical technique." J Bone Joint Surg Am 88 Suppl 1 Pt 2: 322-327.

BACKGROUND: Bone marrow aspirated from the iliac crest contains progenitor cells that can be used to obtain bone-healing of nonunions. However, there is little available information regarding the number and concentration of these cells that are necessary to obtain bone repair. The purpose of this study was to evaluate the number and concentration of progenitor cells that were transplanted for the treatment of nonunion, the callus volume obtained after the transplantation, and the clinical healing rate. METHODS: Marrow was aspirated from both anterior iliac crests, concentrated on a cell separator, and then injected into sixty noninfected atrophic nonunions of the tibia. Each nonunion received a relatively constant volume of 20 cm(3) of concentrated bone marrow. The number of progenitor cells that was transplanted was estimated by counting the fibroblast colony-forming units. The volume of mineralized bone formation was determined by comparing preoperative computerized tomography scans with scans performed four months following the injection. RESULTS: The aspirates contained an average (and standard deviation) of 612 +/- 134 progenitors/cm(3) (range, 12 to 1224 progenitors/cm(3)) before concentration and an average of 2579 +/- 1121 progenitors/cm(3) (range, 60 to 6120 progenitors/cm(3)) after concentration. An average total of 51 x 10(3) fibroblast colony-forming units was injected into each nonunion. Bone union was obtained in fifty-three patients, and the bone marrow that had been injected into the nonunions of those patients contained >1500 progenitors/cm(3) and an average total of 54,962 +/- 17,431 progenitors. The concentration (634 +/- 187 progenitors/cm(3)) and the total number (19,324 +/- 6843) of progenitors injected into the nonunion sites of the seven patients in whom bone union was not obtained were both significantly lower (p = 0.001 and p < 0.01, respectively) than those in the patients who obtained bone union. The volume of the mineralized callus measured at four months on the computerized tomography scans of the patients who had union ranged from 0.8 to 5.3 cm(3) (mean, 3.1 cm(3)). There was a positive correlation between the volume of mineralized callus at four months and the number (p = 0.04) and concentration (p = 0.01) of fibroblast colony-forming units in the graft. There was a negative correlation between the time needed to obtain union and the concentration of fibroblast colony-forming units in the graft (p = 0.04). CONCLUSIONS: Percutaneous autologous bone-marrow grafting is an effective and safe method for the treatment of an atrophic tibial diaphyseal nonunion. However, its efficacy appears to be related to the number of progenitors in the graft, and the number of progenitors available in bone marrow aspirated from the iliac crest appears to be less than optimal in the absence of concentration.

Hernigou, P., et al. (2005). "Percutaneous autologous bone-marrow grafting for nonunions. Influence of the number and concentration of progenitor cells." J Bone Joint Surg Am 87(7): 1430-1437.

Hernigou, P., et al. (2005). "The use of percutaneous autologous bone marrow transplantation in nonunion and avascular necrosis of bone." J Bone Joint Surg Br 87(7): 896-902.

Hernigou, P., et al. (2009). "Cell therapy of hip osteonecrosis with autologous bone marrow grafting." Indian J Orthop 43(1): 40-45.

BACKGROUND: One of the reasons for bone remodeling leading to an insufficient creeping substitution after osteonecrosis in the femoral head may be the small number of progenitor cells in the proximal femur and the trochanteric region. Because of this lack of progenitor cells, treatment modalities should stimulate and guide bone remodeling to sufficient creeping substitution to preserve the integrity of the femoral head. Core decompression with bone graft is used frequently in the treatment of osteonecrosis of the femoral head. In the current series, grafting was done with autologous bone marrow obtained from the iliac crest of patients operated on for early stages of osteonecrosis of the hip before collapse with the hypothesis that before stage of subchondral collapse, increasing the number of progenitor cells in the proximal femur will stimulate bone remodeling and creeping substitution and thereby improve functional outcome. MATERIALS AND METHODS: Between 1990 and 2000, 342 patients (534 hips) with avascular osteonecrosis at early stages (Stages I and II) were treated with core decompression and autologous bone marrow grafting obtained from the iliac crest of patients operated on for osteonecrosis of the hip. The percentage of hips affected by osteonecrosis in this series of 534 hips was 19% in patients taking corticosteroids, 28% in patients with excessive alcohol intake, and 31% in patients with sickle cell disease. The mean age of the patients at the time of decompression and autologous bone marrow grafting was 39 years (range: 16-61 years). The aspirated marrow was reduced in volume by concentration and injected into the femoral head after core decompression with a small trocar. To measure the number of progenitor cells transplanted, the fibroblast colony forming unit was used as an indicator of the stroma cell activity. RESULTS: Patients were followed up from 8 to 18 years. The outcome was determined by the changes in the Harris hip score, progression in radiographic stages, change in volume determined by digitizing area of the necrosis on the different cuts obtained on MRI, and by the need for hip replacement. Total hip replacement was necessary in 94 hips (evolution to collapse) among the 534 hips operated before collapse (Stages I and II). Sixty-nine hips with stage I osteonecrosis of the femoral head at the time of surgery demonstrated total resolution of osteonecrosis based on preoperative and postoperative MRI studies; these hips did not show any changes on plain radiographs. Before treatment, these 69 osteonecrosis had only a marginal band like pattern as abnormal signal and a volume less than 20 cubic centimeters. The intralesional area had kept a normal signal as regards the signal of the femoral head outside the osteonecrosis area. For the 371 other hips without collapse at the most recent follow up (average 12 years), the mean preoperative volume of the osteonecrosis was 26 cm(3) (minimum 12, maximum 30 cm(3)). The mean volume of the abnormal signal measured on MRI at the most recent follow up (mean 12 years) was 12 cm(3). The abnormal signal persisting as a sequelae was seen on T1 images as an intralesional area of low intensity signal with a disappearance of the marginal band like pattern. CONCLUSION: According to our experience, best indication for the procedure is symptomatic hips with osteonecrosis without collapse. In some patients who had Steinberg stage III osteonecrosis (subchondral lucency, no collapse) successful outcomes (no further surgery) has been obtained between 5 to 10 years. Therefore in selected patients, even more advanced disease can be considered for core decompression. Patients who had the greater number of progenitor cells transplanted in their hips had better outcomes.

Hill, J. M., et al. (2005). "Outcomes and risks of granulocyte colony-stimulating factor in patients with coronary artery disease." J Am Coll Cardiol 46(9): 1643-1648.

OBJECTIVES: Cytokine mobilization of progenitor cells from bone marrow may promote myocardial neovascularization with relief of ischemia. BACKGROUND: Patients with coronary artery disease (CAD) have low numbers of endothelial progenitor cells compared with healthy subjects. METHODS: Granulocyte colony-stimulating factor (G-CSF), 10 microg/kg/day for five days, was administered to 16 CAD patients. Progenitor cells were measured by flow cytometry; ischemia was assessed by exercise stress testing and by dobutamine stress cardiac magnetic resonance imaging. RESULTS: Granulocyte colony-stimulating factor increased CD34+/CD133+ cells in the circulation from 1.5 +/- 0.2 microl to 52.4 +/- 10.4 microl (p < 0.001), similar to the response observed in 15 healthy subjects (75.1 +/- 12.6 microl, p = 0.173). Indices of platelet and coagulation activation were not changed by treatment, but C-reactive protein increased from 4.5 +/- 1.3 mg/l to 8.6 +/- 1.3 mg/l (p = 0.017). Two patients experienced serious adverse events: 1) non-ST-segment elevation myocardial infarction (MI) 8 h after the fifth G-CSF dose, and 2) MI and death 17 days after treatment. At 1 month after treatment, there was no improvement from baseline values (i.e., reduction) in wall motion score (from 25.7 +/- 2.1 to 28.3 +/- 1.9, p = 0.196) or segments with abnormal perfusion (7.6 +/- 1.1 to 7.7 +/- 1.1, p = 0.916) and a trend towards a greater number of ischemic segments (from 4.5 +/- 0.6 to 6.1 +/- 1.0, p = 0.068). There was no improvement in exercise duration at 1 month (p = 0.37) or at 3 months (p = 0.98) versus baseline. CONCLUSIONS: Granulocyte colony-stimulating factor administration to CAD patients mobilizes cells with endothelial progenitor potential from bone marrow, but without objective evidence of cardiac benefit and with the potential for adverse outcomes in some patients.

Hisatome, T., et al. (2005). "Neovascularization and bone regeneration by implantation of autologous bone marrow mononuclear cells." Biomaterials 26(22): 4550-4556.

We examined whether transplantation of autologous bone marrow mononuclear cells (BM-MNCs) can augment neovascularization and bone regeneration of bone marrow in femoral bone defects of rabbits. Gelatin microspheres containing basic fibroblast growth factor (bFGF) were prepared for the controlled release of bFGF. To evaluate the in vivo effect of implanted BM-MNCs, we created bone defects in the rabbit medial femoral condyle, and implanted into them 5 x 10(6) fluorescent-labeled autologous BM-MNCs together with gelatin microspheres containing 10 microg bFGF on an atelocollagen gel scaffold. The four experimental groups, which were Atelocollagen gel (Col), Col + 5 x 10(6) BM-MNCs, Col + 10 microg bFGF, and Col + 5 x 10(6) BM-MNCs + 10 microg bFGF, were implanted into the sites of the prepared defects using Atelocollagen gel as a scaffold. The autologous BM-MNCs expressed CD31, an endothelial lineage cell marker, and induced efficient neovascularization at the implanted site 2 weeks after implantation. Capillary density in Col + BM-MNCs + bFGF was significantly large compared with other groups. This combination also enhanced regeneration of the bone defect after 8 weeks to a significantly greater extent than either BM-MNCs or bFGF on their own. In summary, these findings demonstrate that a combination of BM-MNCs and bFGF gelatin hydrogel enhance the neovascularization and the osteoinductive ability, resulting in bone regeneration.

Hofmann, T. J., et al. (2013) Transplanted Murine Long-term Repopulating Hematopoietic Cells Can Differentiate to Osteoblasts in the Marrow Stem Cell Niche. Mol Ther DOI: 10.1038/mt.2013.36

Bone marrow transplantation (BMT) can give rise to donor-derived osteopoiesis in mice and humans; however, the source of this activity, whether a primitive osteoprogenitor or a transplantable marrow cell with dual hematopoietic and osteogenic potential, has eluded detection. To address this issue, we fractionated whole BM from mice according to cell surface immunophenotype and assayed the hematopoietic and osteopoietic potentials of the transplanted cells. Here, we show that a donor marrow cell capable of robust osteopoiesis possesses a surface phenotype of c-Kit+ Lin- Sca-1+ CD34-/lo, identical to that of the long-term repopulating hematopoietic stem cell (LTR-HSC). Secondary BMT studies demonstrated that a single marrow cell able to contribute to hematopoietic reconstitution in primary recipients also drives robust osteopoiesis and LT hematopoiesis in secondary recipients. These findings indicate that LTR-HSC can give rise to progeny that differentiate to osteoblasts after BMT, suggesting a mechanism for prompt restoration of the osteoblastic HSC niche following BM injury, such as that induced by clinical BMT preparative regimens. An understanding of the mechanisms that regulate this differentiation potential may lead to novel treatments for disorders of bone as well as methods for preserving the integrity of endosteal hematopoietic niches.Molecular Therapy (2013); doi:10.1038/mt.2013.36.

Horwitz, E. M. (2003). "Stem cell plasticity: the growing potential of cellular therapy." Arch Med Res 34(6): 600-606.

The fundamental principle of stem cell biology is that cells with the potential for both self-renewal and terminal differentiation into one or more cell types may be found in a given tissue. The corollary of this principle is that the stem cells give rise to tissues in which they reside, the so-called expected tissues. Many exciting discoveries reported over the last several years challenge this paradigm by showing that there are not only tissue-specific stem cells that differentiate to the expected mature cells, but also that tissue stem cells can differentiate into unexpected cell lineages, suggesting an enormous plasticity of differentiation. Hematopoietic stem cells, which have drawn the most attention, mesenchymal stem cells, and neural stem cells have been the focus of many investigations. However, recent studies directed toward hematopoietic stem cells have disputed the concept of stem cell plasticity, suggesting that experimental artifact or somatic cell fusion may account for reported observations of plasticity. Although the data are mounting, stem cell plasticity, strictly defined, has yet to be rigorously proven. Animal models to meticulously define the biology and potential plasticity of stem cells and pilot clinical trials to begin to explore the biology and therapeutic potential of human stem cells will both be vital to advance the field over the coming years.

Horwitz, E. M. and A. Keating (2000). "Nonhematopoietic mesenchymal stem cells: what are they?" Cytotherapy 2(5): 387-388.

Horwitz, E. M., et al. (1999). "Transplantability and therapeutic effects of bone marrow-derived mesenchymal cells in children with osteogenesis imperfecta." Nat Med 5(3): 309-313.

In principle, transplantation of mesenchymal progenitor cells would attenuate or possibly correct genetic disorders of bone, cartilage and muscle, but clinical support for this concept is lacking. Here we describe the initial results of allogeneic bone marrow transplantation in three children with osteogenesis imperfecta, a genetic disorder in which osteoblasts produce defective type I collagen, leading to osteopenia, multiple fractures, severe bony deformities and considerably shortened stature. Three months after osteoblast engraftment (1.5-2.0% donor cells), representative specimens of trabecular bone showed histologic changes indicative of new dense bone formation. All patients had increases in total body bone mineral content ranging from 21 to 29 grams (median, 28), compared with predicted values of 0 to 4 grams (median, 0) for healthy children with similar changes in weight. These improvements were associated with increases in growth velocity and reduced frequencies of bone fracture. Thus, allogeneic bone marrow transplantation can lead to engraftment of functional mesenchymal progenitor cells, indicating the feasibility of this strategy in the treatment of osteogenesis imperfecta and perhaps other mesenchymal stem cell disorders as well.

Hristov, M., et al. (2003). "Endothelial progenitor cells: isolation and characterization." Trends Cardiovasc Med 13(5): 201-206.

Bone marrow of adults contains a subtype of progenitor cells that have the capacity to differentiate into mature endothelial cells and have therefore been termed endothelial progenitor cells (EPCs). Of the three cell markers (CD133, CD34, and the vascular endothelial growth factor receptor 2) that characterize the early functional EPCs, located predominantly in the bone marrow, EPCs obviously lose CD133/CD34 and start to express CD31, vascular endothelial cadherin, and von Willebrand factor when migrating to the circulation. Various isolation procedures of EPCs from different sources by using adherence culture or magnetic microbeads have been described, but published findings with regard to the number of EPCs in the peripheral circulation of healthy adults are scanty and no data regarding the lifetime of EPCs in vivo exist. Clinical studies employing EPCs for neovascularization of ischemic organs have just been started; however, the mechanisms stimulating or inhibiting the differentiation of bone marrow-derived EPCs in vivo and the signals causing their adhesion, migration, and homing to sites of injured tissue are largely unknown at present.

Hristov, M., et al. (2003). "Endothelial progenitor cells: mobilization, differentiation, and homing." Arterioscler Thromb Vasc Biol 23(7): 1185-1189.

Postnatal bone marrow contains a subtype of progenitor cells that have the capacity to migrate to the peripheral circulation and to differentiate into mature endothelial cells. Therefore, these cells have been termed endothelial progenitor cells (EPCs). The isolation of EPCs by adherence culture or magnetic microbeads has been described. In general, EPCs are characterized by the expression of 3 markers, CD133, CD34, and the vascular endothelial growth factor receptor-2. During differentiation, EPCs obviously lose CD133 and start to express CD31, vascular endothelial cadherin, and von Willebrand factor. EPCs seem to participate in endothelial repair and neovascularization of ischemic organs. Clinical studies using EPCs for neovascularization have just been started; however, the mechanisms stimulating or inhibiting the differentiation of EPC in vivo and the signals causing their migration and homing to sites of injured endothelium or extravascular tissue are largely unknown at present. Thus, future studies will help to explore areas of potential basic research and clinical application of EPCs.

Hsu, Y. C. and E. Fuchs (2012). "A family business: stem cell progeny join the niche to regulate homeostasis." Nat Rev Mol Cell Biol 13(2): 103-114.

Stem cell niches, the discrete microenvironments in which the stem cells reside, play a dominant part in regulating stem cell activity and behaviours. Recent studies suggest that committed stem cell progeny become indispensable components of the niche in a wide range of stem cell systems. These unexpected niche inhabitants provide versatile feedback signals to their stem cell parents. Together with other heterologous cell types that constitute the niche, they contribute to the dynamics of the microenvironment. As progeny are often located in close proximity to stem cell niches, similar feedback regulations may be the underlying principles shared by different stem cell systems.

Hu, S. L., et al. (2010). "Functional recovery in acute traumatic spinal cord injury after transplantation of human umbilical cord mesenchymal stem cells." Crit Care Med 38(11): 2181-2189.

OBJECTIVE: Spinal cord injury results in loss of neurons, degeneration of axons, formation of glial scar, and severe functional impairment. Human umbilical cord mesenchymal stem cells can be induced to form neural cells in vitro. Thus, these cells have a potential therapeutic role for treating spinal cord injury. DESIGN AND SETTING: Rats were randomly divided into three groups: sham operation group, control group, and human umbilical cord mesenchymal stem cell group. All groups were subjected to spinal cord injury by weight drop device except for sham group. SUBJECTS: Thirty-six female Sprague-Dawley rats. INTERVENTIONS: The control group received Dulbecco's modified essential media/nutrient mixture F-12 injections, whereas the human umbilical cord mesenchymal stem cell group undertook cells transplantation at the dorsal spinal cord 2 mm rostrally and 2 mm caudally to the injury site at 24 hrs after spinal cord injury. MEASUREMENTS: Rats from each group were examined for neurologic function and contents of brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, and neurotrophin-3. Survival, migration, and differentiation of human umbilical cord mesenchymal stem cells, regeneration of axons, and formation of glial scar were also explored by using immunohistochemistry and immunofluorescence. MAIN RESULTS: Recovery of hindlimb locomotor function was significantly enhanced in the human umbilical cord mesenchymal stem cells grafted animals at 5 wks after transplantation. This recovery was accompanied by increased length of neurofilament-positive fibers and increased numbers of growth cone-like structures around the lesion site. Transplanted human umbilical cord-mesenchymal stem cells survived, migrated over short distances, and produced large amounts of glial cell line-derived neurotrophic factor and neurotrophin-3 in the host spinal cord. There were fewer reactive astrocytes in both the rostral and caudal stumps of the spinal cord in the human umbilical cord-mesenchymal stem cell group than in the control group. CONCLUSIONS: Treatment with human umbilical cord mesenchymal stem cells can facilitate functional recovery after traumatic spinal cord injury and may prove to be a useful therapeutic strategy to repair the injured spinal cord.

Huang, J. I. and V. M. Goldberg (2009). Orthopedic Applications of Stem Cells. Essentials of Stem Cell Biology. R. Lanza, J. Gearhart, B. Hogan et al. San Diego, Academic Press/Elsevier: 561-569.

Ichim, T. E., et al. (2010). "Feasibility of combination allogeneic stem cell therapy for spinal cord injury: a case report." Int Arch Med 3: 30.

Cellular therapy for spinal cord injury (SCI) is overviewed focusing on bone marrow mononuclear cells, olfactory ensheathing cells, and mesenchymal stem cells. A case is made for the possibility of combining cell types, as well as for allogeneic use. We report the case of 29 year old male who suffered a crush fracture of the L1 vertebral body, lacking lower sensorimotor function, being a score A on the ASIA scale. Stem cell therapy comprised of intrathecal administration of allogeneic umbilical cord blood ex-vivo expanded CD34 and umbilical cord matrix MSC was performed 5 months, 8 months, and 14 months after injury. Cell administration was well tolerated with no adverse effects observed. Neuropathic pain subsided from intermittent 10/10 to once a week 3/10 VAS. Recovery of muscle, bowel and sexual function was noted, along with a decrease in ASIA score to "D". This case supports further investigation into allogeneic-based stem cell therapies for SCI.

Im, G. I., et al. (2005). "Do adipose tissue-derived mesenchymal stem cells have the same osteogenic and chondrogenic potential as bone marrow-derived cells?" OsteoArthritis and Cartilage 13: 845-853.

Objective: Adipose tissue-derived mesenchymal stem cells (ATMSCs) have been shown to differentiate into bone, cartilage, fat or muscle.

However, it is not certain that ATMSCs are equal to bone marrow-derived mesenchymal stem cells (BMMSC) for their bone and cartilage

forming potential. The purpose of this study was to answer the question.

Methods: BMMSCs were obtained from the medullary canal of femur and ATMSCs were isolated from the fat harvested during liposuction

procedures. After cell expansion in culture media and two passages, the immunofluorescent studies for STRO-1 and CD34 were performed to

characterize the BMMSCs and ATMSCs. Osteogenesis was induced on a monolayer culture with osteogenic medium containing

dexamethasone, b-glycerophosphate and ascorbate. After 2e3 weeks, alkaline phosphatase (AP) and Von Kossa staining were done. To test

for chondrogenesis, mesenchymal stem cells (MSCs) were cultured in a pellet culture and in a fibrin scaffold with a chondrogenic medium

(CM) containing transforming growth factor-b2 and insulin-like growth factor-I. After 4 weeks, Safranin-O staining and immunohistochemical

staining for type II collagen were done to evaluate the chondrogenic differentiation and the matrix production. A histological scale was used to

semiquantitatively assess the degree of chondrogenesis.

Results: Both BMMSCs and ATMSCs were STRO-1 positive and CD34 negative. On the test of osteogenesis, the osteoblastic differentiation

of ATMSCs as demonstrated by AP staining was much less than that of the BMMSCs (PZ0.002). The amount of matrix mineralization shown

by Von Kossa staining also showed statistical differences between the two MSCs (PZ0.011). On the test for chondrogenesis by the pellet

culture ATMSCs showed much weaker presentation as chondrogenic cells in both cell morphology and the matrix production. The histological

score was 6.5 (SD1.3) for the BMMSCs, and 4.3 (SD1.6) for the ATMSCs cultured in CM, which was statistically significant (PZ0.023). The

results from fibrin gel paralleled those from the pellet culture in general.

Conclusion: The results of our study suggest that the ATMSCs may have an inferior potential for both osteogenesis and chondrogenesis

compared with the BMMSCs, and these cast doubts on the value of adipose tissue as a source of MSCs.

Key words: Mesenchymal stem cell, Osteogenesis, Chondrogenesis, Adipose tissue, Bone marrow.

Imai, H., et al. (2009). "The insight of revascularization mechanism based on angiogenesis and arteriogenesis from the experimental and clinical works in moyamoya disease." Journal of Cerebral Blood Flow & Metabolism(29): S377-S378.

Infante-Cossio, P., et al. (2011). "Myxofibroma of the maxilla. Reconstruction with iliac crest graft and dental implants after tumor resection." Med Oral Patol Oral Cir Bucal 16(4): e532-536.

Odontogenic fibromyxomas are benign odontogenic tumors of mesenchymal origin of rare presentation in the oral cavity, which exhibit locally aggressive behavior and are prone to local recurrence. The controversy has mainly been on therapeutic management with recommendations varying, depending on the clinical cases, from simple curettage of lesion to segmental bone resection. We present a case report describing the reconstruction of an osseous defect in the maxilla and the restoration with dental implants in a 32 year old female patient after radical surgical excision due to an odontogenic fibromyxoma with locally aggressive behavior. The primary reconstruction of maxillary discontinuity defect was carried out by an immediate non-vascularized cortico-cancellous iliac crest graft. Using a computer-guided system for the implant treatment-planning, three dental implants were secondary placed in the bone graft by means of flapless implant surgery. The patient was subsequently restored with an implant-supported fixed prosthesis that has remained in continuous function for a period of three years. The surgical, reconstructive and restorative treatment sequence and techniques are discussed.

Jackson, I. T. (2005). "S. R. Coleman: Structural Fat Grafting." Eur J Plast Surg 27: 354.

Jager, M., et al. (2010). "Cell therapy in bone healing disorders." Orthop Rev (Pavia) 2(2): 79-87.

In addition to osteosynthetic stabilizing techniques and autologous bone transplantations, so-called orthobiologics play an increasing role in the treatment of bone healing disorders. Besides the use of various growth factors, more and more new data suggest that cell-based therapies promote local bone regeneration. For ethical and biological reasons, clinical application of progenitor cells on the musculoskeletal system is limited to autologous, postpartum stem cells. Intraoperative one-step treatment with autologous progenitor cells, in particular, delivered promising results in preliminary clinical studies. This article provides an overview of the rationale for, and characteristics of the clinical application of cell-based therapy to treat osseous defects based on a review of existing literature and our own experience with more than 100 patients. Most clinical trials report successful bone regeneration after the application of mixed cell populations from bone marrow. The autologous application of human bone marrow cells which are not expanded ex vivo has medico-legal advantages. However, there is a lack of prospective randomized studies including controls for cell therapy for bone defects. Autologous bone marrow cell therapy seems to be a promising treatment option which may reduce the amount of bone grafting in future.

Jin, H., et al. (2012). "The effects of autologous bone marrow mesenchymal stem cell arterial perfusion on vascular repair and angiogenesis in osteonecrosis of the femoral head in dogs." Int Orthop 36(12): 2589-2596.

PURPOSE: The purpose of this study was to observe the effects of marrow mesenchymal stem cell (MSCs) arterial perfusion on vascular repair and angiogenesis in osteonecrosis of the femoral head (ONFH). METHODS: Twelve healthy male adult Beagle dogs were randomly divided into two groups: group A (the control group) and group B (the MSCs arterial perfusion group). ONFH animal models were established by hip dislocation and liquid nitrogen. At the same time, MSCs were obtained, cultured and proliferated. After three weeks, arterial perfusion was performed in all animals. Group B was given 1 ml MSCs (5 x 10(6)-1 x 10(7)/ml), while 0.9 % normal saline was used in group A. After four weeks or eight weeks, the dogs were put to death. The changes of main arteries, the expression of vascular endothelial growth factor (VEGF), VEGF mRNA and microvessel density (MVD) of ONFH were observed. All the data were analysed by SPSS13.0. RESULTS: In digital subtraction angiography (DSA), after four or eight weeks of treatment, the quantity and diameter of the main arteries of the femoral head in group B were improved, compared to group A (P < 0.05,P < 0.01). Concerning histology and immunohistochemistry, after four or eight weeks of treatment, the expression of VEGF and MVD were significantly higher than that of group A (P < 0.05, P < 0.01). For real-time quantitative polymerase chain reaction (RT-PCR), after four or eight weeks of treatment, the expression of VEGF mRNA in group B was significantly higher than that of group A (P < 0.05, P < 0.01), and after eight weeks of treatment, the expression of VEGF mRNA were significantly higher than that of four-weeks treatment in group A (P <0.01). CONCLUSIONS: MSCs arterial perfusion can promote vascular repair and angiogenesis and then improve blood supply and repair of femoral head.

Johansson, C. B., et al. (2008). "Extensive fusion of haematopoietic cells with Purkinje neurons in response to chronic inflammation." Nat Cell Biol 10(5): 575-583.

Transplanted bone marrow-derived cells (BMDCs) have been reported to fuse with cells of diverse tissues, but the extremely low frequency of fusion has led to the view that such events are biologically insignificant. Nonetheless, in mice with a lethal recessive liver disease (tyrosinaemia), transplantation of wild-type BMDCs restored liver function by cell fusion and prevented death, indicating that cell fusion can have beneficial effects. Here we report that chronic inflammation resulting from severe dermatitis or autoimmune encephalitis leads to robust fusion of BMDCs with Purkinje neurons and formation of hundreds of binucleate heterokaryons per cerebellum, a 10-100-fold higher frequency than previously reported. Single haematopoietic stem-cell transplants showed that the fusogenic cell is from the haematopoietic lineage and parabiosis experiments revealed that fusion can occur without irradiation. Transplantation of rat bone marrow into mice led to activation of dormant rat Purkinje neuron-specific genes in BMDC nuclei after fusion with mouse Purkinje neurons, consistent with nuclear reprogramming. The precise neurological role of these heterokaryons awaits elucidation, but their frequency in brain after inflammation is clearly much higher than previously appreciated.

Johnson, R. G. (2014). "Bone marrow concentrate with allograft equivalent to autograft in lumbar fusions." Spine (Phila Pa 1976) 39(9): 695-700.

STUDY DESIGN: Prospective randomized study. OBJECTIVE: To compare autologous bone marrow concentrate mixed with allograft cancellous bone to iliac crest autograft in lumbar fusions. SUMMARY OF BACKGROUND DATA: Bone marrow has been shown to be a rich source of osteoprogenitor cells. Osteoprogenitor cells have been shown in animals, and some human studies, to have potential in use as a bone graft substitute. METHODS: Twenty-five patients underwent from 1- to 3-level lumbar fusions. One patient was lost to follow-up. On one half of the spine, allograft plus autologous bone marrow concentrate was used, whereas on the other half, autologous iliac crest bone was used. Cellular analysis, consisting of nucleated cell count, mononuclear cell count, CD34 count, and colony-forming-units-fibroblast count, was done on marrow aspirates and concentrates. At 1 year postoperation, computed tomographic scans of the fusions were evaluated on a blinded basis by 2 neuroradiologists independent of each other. Radiographical fusion was the primary outcome measure. RESULTS: There was no statistical difference in fusion scores between allograft and autograft in the lateral gutters, interbody cages, or facet joints. There was a positive trend between CD34 counts and radiographical fusion. CONCLUSION: The study shows equivalence between cancellous allograft mixed with bone marrow concentrate and autologous iliac crest bone for lumbar fusions.

Jopling, C., et al. (2011). "Dedifferentiation, transdifferentiation and reprogramming: three routes to regeneration." Nat Rev Mol Cell Biol 12(2): 79-89.

The ultimate goal of regenerative medicine is to replace lost or damaged cells. This can potentially be accomplished using the processes of dedifferentiation, transdifferentiation or reprogramming. Recent advances have shown that the addition of a group of genes can not only restore pluripotency in a fully differentiated cell state (reprogramming) but can also induce the cell to proliferate (dedifferentiation) or even switch to another cell type (transdifferentiation). Current research aims to understand how these processes work and to eventually harness them for use in regenerative medicine.

Jung, K. H., et al. (2008). "Circulating endothelial progenitor cells as a pathogenetic marker of moyamoya disease." J Cereb Blood Flow Metab 28(11): 1795-1803.

Moyamoya disease (MMD) is an unusual form of chronic cerebrovascular occlusive disease that involves the formation of characteristically abnormal vessels. Recent studies have reported that colony-forming unit (CFU) and outgrowth cells represent a subpopulation of endothelial progenitor cells (EPCs). Here, we attempted to determine the significance of CFU number and outgrowth cell yield in MMD. Endothelial progenitor cells were isolated from the blood of 24 adult MMD patients and from 48 age- and risk factor-matched control subjects. After 7 days of culture, CFUs were determined, and yields of outgrowth cells were measured during 2 months of culture. The EPC function was also evaluated using matrigel plate assays. It was found that CFU numbers were significantly lower in MMD patients than in controls. Moreover, during long-term culture, outgrowth cells were isolated from only 10% of control subjects but from 33% of MMD patients, and CFU numbers and tube formation were found to be lower in advanced MMD cases than in those with early stage disease, whereas outgrowth cells were more frequently detected in those with early MMD and moyamoya vessels than in those with advanced disease. These characteristics of circulating EPCs reflect mixed conditions of vascular occlusion and abnormal vasculogenesis during the pathogenesis of MMD.

Jung, Y., et al. (2008). "Hematopoietic stem cells regulate mesenchymal stromal cell induction into osteoblasts thereby participating in the formation of the stem cell niche." Stem Cells 26(8): 2042-2051.

Crosstalk between hematopoietic stem cells (HSCs) and the cells comprising the niche is critical for maintaining stem cell activities. Yet little evidence supports the concept that HSCs regulate development of the niche. Here, the ability of HSCs to directly regulate endosteal development was examined. Marrow was isolated 48 hours after "stressing" mice with a single acute bleed or from control nonstressed animals. "Stressed" and "nonstressed" HSCs were cocultured with bone marrow stromal cells to map mesenchymal fate. The data suggest that HSCs are able to guide mesenchymal differentiation toward the osteoblastic lineage under basal conditions. HSCs isolated from animals subjected to an acute stress were significantly better at inducing osteoblastic differentiation in vitro and in vivo than those from control animals. Importantly, HSC-derived bone morphogenic protein 2 (BMP-2) and BMP-6 were responsible for these activities. Furthermore, significant differences in the ability of HSCs to generate a BMP response following stress were noted in aged and in osteoporotic animals. Together these data suggest a coupling between HSC functions and bone turnover as in aging and in osteoporosis. For the first time, these results demonstrate that HSCs do not rest passively in their niche. Instead, they directly participate in bone formation and niche activities. Disclosure of potential conflicts of interest is found at the end of this article.

Jung, Y., et al. (2005). "Cell-to-cell contact is critical for the survival of hematopoietic progenitor cells on osteoblasts." Cytokine 32(3-4): 155-162.

Osteoblasts constitute part of the stromal cell support system in marrow for hematopoiesis, however little is known as to how they interact with hematopoietic stem cells (HSCs). In vitro studies have demonstrated that the survival of HSCs in co-culture with osteoblasts requires intimate cell-to-cell contact. This suggests that the osteoblast-derived factor(s) that supports stem cell activities are produced in very small quantities, are rapidly turned over, may be membrane-anchored and/or require the engagement of cell-cell adhesion molecules that are yet to be determined. In the present report we found that the survival of hematopoietic progenitor cells on osteoblasts is dependent upon the engagement of VLA-4 (alpha4beta1) and VLA-5 (alpha5beta1) receptors using function blocking antibodies. Cell-to-cell contact is required to support progenitor activity, but can be replaced if receptor-ligand engagement of the VLA-4 and LFA-1 complexes is provided through the use of recombinant ligands (fibronectin, ICAM-1, VCAM-1). Moreover, once these receptors were engaged, conditioned medium derived from HSCs grown on osteoblast ligands supported significantly greater hematopoietic progenitors in vitro than did osteoblast-conditioned or HSC-conditioned medium alone. While the molecules present in the co-cultured medium remain to be identified, the data suggest that hematopoietic cells cooperate with osteoblasts to assemble the various marrow microenvironments by directing the synthesis of osteoblast-derived cytokines to improve HSC survival.

Kale, S., et al. (2003). "Bone marrow stem cells contribute to repair of the ischemically injured renal tubule." J Clin Invest 112(1): 42-49.

The paradigm for recovery of the renal tubule from acute tubular necrosis is that surviving cells from the areas bordering the injury must migrate into the regions of tubular denudation and proliferate to re-establish the normal tubular epithelium. However, therapies aimed at stimulating these events have failed to alter the course of acute renal failure in human trials. In the present study, we demonstrate that Lin-Sca-1+ cells from the adult mouse bone marrow are mobilized into the circulation by transient renal ischemia and home specifically to injured regions of the renal tubule. There they differentiate into renal tubular epithelial cells and appear to constitute the majority of the cells present in the previously necrotic tubules. Loss of stem cells following bone marrow ablation results in a greater rise in blood urea nitrogen after renal ischemia, while stem cell infusion after bone marrow ablation reverses this effect. Thus, therapies aimed at enhancing the mobilization, propagation, and/or delivery of bone marrow stem cells to the kidney hold potential as entirely new approaches for the treatment of acute tubular necrosis.

Kara, R. J., et al. (2012). "Fetal cells traffic to injured maternal myocardium and undergo cardiac differentiation." Circ Res 110(1): 82-93.

RATIONALE: Fetal cells enter the maternal circulation during pregnancy and may persist in maternal tissue for decades as microchimeras. OBJECTIVE: Based on clinical observations of peripartum cardiomyopathy patients and the high rate of recovery they experience from heart failure, our objective was to determine whether fetal cells can migrate to the maternal heart and differentiate to cardiac cells. METHODS AND RESULTS: We report that fetal cells selectively home to injured maternal hearts and undergo differentiation into diverse cardiac lineages. Using enhanced green fluorescent protein (eGFP)-tagged fetuses, we demonstrate engraftment of multipotent fetal cells in injury zones of maternal hearts. In vivo, eGFP+ fetal cells form endothelial cells, smooth muscle cells, and cardiomyocytes. In vitro, fetal cells isolated from maternal hearts recapitulate these differentiation pathways, additionally forming vascular tubes and beating cardiomyocytes in a fusion-independent manner; approximately 40% of fetal cells in the maternal heart express Caudal-related homeobox2 (Cdx2), previously associated with trophoblast stem cells, thought to solely form placenta. CONCLUSIONS: Fetal maternal stem cell transfer appears to be a critical mechanism in the maternal response to cardiac injury. Furthermore, we have identified Cdx2 cells as a novel cell type for potential use in cardiovascular regenerative therapy.

Karsenty, G. (2009). Cell differentiation in the skeleton. Essentials of Stem Cell Biology. San Diego, CA, Elsevier: 223-226.

Keats, E. C. and Z. A. Khan (2012). "Vascular stem cells in diabetic complications: evidence for a role in the pathogenesis and the therapeutic promise." Cardiovasc Diabetol 11(1): 37.

ABSTRACT: Long standing diabetes leads to structural and functional alterations in both the micro- and the macro-vasculature. Vascular endothelial cells (ECs) are the primary target of the hyperglycemia-induced adverse effects. Vascular stem cells that give rise to endothelial progenitor cells (EPCs) and mesenchymal progenitor cells (MPCs) represent an attractive target for cell therapy for diabetic patients. A number of studies have reported EPC dysfunction as a novel participant in the culmination of the diabetic complications. The controversy behind the identity of EPCs and the similarity between these progenitor cells to hematopoietic cells has led to conflicting results. MPCs, on the other hand, have not been examined for a potential role in the pathogenesis of the complications. These multipotent cells, however, do show a therapeutic role. In this article, we summarize the vascular changes that occur in diabetic complications highlighting some of the common features, the key findings that illustrate an important role of vascular stem cells (VSCs) in the pathogenesis of chronic diabetic complications, and provide mechanisms by which these cells can be used for therapy.

Kellogg, J. X. (2007). Anterior lumbar interbody fusion treated with concentrated autologous adult stem cells (BMAC) and cancellous bone chips. Portland, OR: 1.

Kellogg, J. X. (2008). Anterior lumbar interbody fusion following complete L4-L5 anterior discectomy treated with concentrated autologous adult stem cells (BMAC) and synthetic cancellous bone void filler. Portland, OR: 1.

Kevy, S. V., et al. (2006). Point of Care Concentration of Bone Marrow. Orthopedic Research Society.

Kevy, S. V., et al. (2009). Platelet-Rich Plasma: Questions and Answers, Immune Disease Institute, Department of Orthopedics at Children's Hospital; BioSciences Research, Cambridge, MA.

Khan, S. N., et al. (2005). "Use of osteopromotive growth factors, demineralized bone matrix, and ceramics to enhance spinal fusion." J Am Acad Orthop Surg 13(2): 129-137.

Recently developed materials that can enhance fusion rates for posterolateral lumbar arthrodesis may be used alone or in combination with autogenous bone grafts. Novel osteopromotive growth factor preparations are currently under scrutiny; these include autogenous growth factor concentrate, bovine bone-derived osteoinductive protein, and recombinant human MP52. Demineralized bone matrix products may enhance or extend grafts. However, few studies, especially prospective randomized clinical trials, have assessed their efficacy, so it is difficult to compare formulations. Ceramics have been evaluated in animal studies and human clinical trials for a variety of applications in spinal surgery. These materials function best as bone graft extenders or as bioactive osteoinductive material carriers in posterolateral lumbar fusions. They have the advantage of variable porosity, low cost, and ease of manufacture. Hydroxyapatite/tricalcium phosphate ceramics have been shown to perform as well as autogenous bone grafts but with fewer complications.

Kollet, O., et al. (2002). "Human CD34(+)CXCR4(-) sorted cells harbor intracellular CXCR4, which can be functionally expressed and provide NOD/SCID repopulation." Blood 100(8): 2778-2786.

Homing and repopulation of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice by enriched human CD34(+) stem cells from cord blood, bone marrow, or mobilized peripheral blood are dependent on stromal cell-derived factor 1 (SDF-1)/CXCR4 interactions. Recently, human cord and fetal blood CD34(+)CD38(-)CXCR4(-) and CXCR4(+) cells, sorted with neutralizing anti-CXCR4 monoclonal antibody (mAb), were shown to have similar NOD/SCID repopulation potential. Herein we report that human cord blood CD34(+)CXCR4(+) (R4(+)) and CD34(+)CXCR4(-) (R4(-)) subsets, sorted with neutralizing anti-CXCR4 mAb, engrafted NOD/SCID mice with significantly lower levels of human cells compared with nonsorted and SDF-1-migrated CD34(+) cells. Coinjection of purified cells with 10 microg anti-CXCR4 mAb significantly reduced engraftment of all CD34(+) subsets, and 50 microg completely abrogated engraftment by R4(-) and CD34(+) cells. Importantly, R4(-) cells harbor intracellular CXCR4, which can be rapidly induced to cell surface expression within a few hours. Moreover, 48 hours of cytokine stimulation resulted in up-regulation of both cell surface and intracellular CXCR4, restoring migration capacities toward a gradient of SDF-1 and high-level NOD/SCID repopulation potential. In addition, homing of sorted R4(-) cells into the murine bone marrow and spleen was significantly slower and reduced compared to CD34(+) cells but yet CXCR4 dependent. In conclusion, R4(-) cells express intracellular CXCR4, which can be functionally expressed on the cell membrane to mediate SDF-1-dependent homing and repopulation. Our results suggest dynamic CXCR4 expression on CD34(+) stem and progenitor cells, regulating their motility and repopulation capacities.

Kollet, O., et al. (2003). "HGF, SDF-1, and MMP-9 are involved in stress-induced human CD34+ stem cell recruitment to the liver." J Clin Invest 112(2): 160-169.

Hematopoietic stem cells rarely contribute to hepatic regeneration, however, the mechanisms governing their homing to the liver, which is a crucial first step, are poorly understood. The chemokine stromal cell-derived factor-1 (SDF-1), which attracts human and murine progenitors, is expressed by liver bile duct epithelium. Neutralization of the SDF-1 receptor CXCR4 abolished homing and engraftment of the murine liver by human CD34+ hematopoietic progenitors, while local injection of human SDF-1 increased their homing. Engrafted human cells were localized in clusters surrounding the bile ducts, in close proximity to SDF-1-expressing epithelial cells, and differentiated into albumin-producing cells. Irradiation or inflammation increased SDF-1 levels and hepatic injury induced MMP-9 activity, leading to both increased CXCR4 expression and SDF-1-mediated recruitment of hematopoietic progenitors to the liver. Unexpectedly, HGF, which is increased following liver injury, promoted protrusion formation, CXCR4 upregulation, and SDF-1-mediated directional migration by human CD34+ progenitors, and synergized with stem cell factor. Thus, stress-induced signals, such as increased expression of SDF-1, MMP-9, and HGF, recruit human CD34+ progenitors with hematopoietic and/or hepatic-like potential to the liver of NOD/SCID mice. Our results suggest the potential of hematopoietic CD34+/CXCR4+cells to respond to stress signals from nonhematopoietic injured organs as an important mechanism for tissue targeting and repair.

Kon, E., et al. (2011). "Platelet-rich plasma intra-articular injection versus hyaluronic acid viscosupplementation as treatments for cartilage pathology: from early degeneration to osteoarthritis." Arthroscopy 27(11): 1490-1501.

PURPOSE: The aim of our study is to compare the efficacy of platelet-rich plasma (PRP) and viscosupplementation (hyaluronic acid [HA]) intra-articular injections for the treatment of knee cartilage degenerative lesions and osteoarthritis (OA). METHODS: The study involved 150 patients affected by cartilage degenerative lesions and early and severe OA. Fifty symptomatic patients were treated with 3 autologous PRP intra-articular injections and were evaluated prospectively at enrollment and at 2- and 6-month follow-up. The results obtained were compared with 2 homogeneous groups of patients treated with HA injections. One group was treated with injections of high-molecular weight HA; the other group was treated with low-molecular weight (LW) HA. International Knee Documentation Committee and EQ VAS scores were used for clinical evaluation; adverse events and patient satisfaction were also recorded. RESULTS: At 2 months' follow-up, the PRP and LW HA groups showed a similar improvement, with higher results compared with the high-molecular weight HA group (P < .005). At 6 months' follow-up, better results were observed in the PRP group (P < .005). PRP and LW HA treatments offered similar results in patients aged over 50 years and in the treatment of advanced OA. PRP showed a better performance compared with HA in younger patients affected by cartilage lesions or early OA. CONCLUSIONS: Autologous PRP injections showed more and longer efficacy than HA injections in reducing pain and symptoms and recovering articular function. Better results were achieved in younger and more active patients with a low degree of cartilage degeneration, whereas a worse outcome was obtained in more degenerated joints and in older patients, in whom results similar to those of viscosupplementation have been observed. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Kon, E., et al. (2012). "How to treat osteochondritis dissecans of the knee: Surgical techniques and new trends." J Bone Joint Surg Am 94(e1): 1-8.

Background: Osteochondritis dissecans is a relatively common cause of knee pain. The aim of this study was to

describe the outcomes of five different surgical techniques in a series of sixty patients with osteochondritis dissecans.

Methods: Sixty patients (age 22.4 ± 7.4 years, sixty-two knees) with osteochondritis dissecans of a femoral condyle

(forty-five medial and seventeen lateral) were treated with osteochondral autologous transplantation, autologous chondrocyte

implantation with bone graft, biomimetic nanostructured osteochondral scaffold (MaioRegen) implantation, bonecartilage

paste graft, or a ‘‘one-step’’ bone-marrow-derived cell transplantation technique. Preoperative and follow-up

evaluation included the International Knee Documentation Committee (IKDC) score, the EuroQol visual analog scale

(EQ-VAS) score, radiographs, and magnetic resonance imaging.

Results: The global mean IKDC score improved from 40.1 ± 14.3 preoperatively to 77.2 ± 21.3 (p < 0.0005) at 5.3 ± 4.7

years of follow-up, and the EQ-VAS improved from 51.7 ± 17.0 to 83.5 ± 18.3 (p < 0.0005). No influence of age, lesion

size, duration of follow-up, or previous surgical procedures on the result was found. The only difference among the results

of the surgical procedures was a trend toward better results following autologous chondrocyte implantation (p = 0.06).

Conclusions: All of the techniques were effective in achieving good clinical and radiographic results in patients with

osteochondritis dissecans, and the effectiveness of autologous chondrocyte implantation was confirmed at a mean

follow-up of five years. Newer techniques such as MaioRegen implantation and the ‘‘one-step’’ transplantation technique

are based on different rationales; the first relies on the characteristics of the scaffold and the second on the regenerative

potential of mesenchymal cells. Both of these newer procedures have the advantage of being minimally invasive and

requiring a single operation.

Koob, T. J., et al. (2013). "Biological properties of dehydrated human amnion/chorion composite graft: implications for chronic wound healing." Int Wound J.

Human amnion/chorion tissue derived from the placenta is rich in cytokines and growth factors known to promote wound healing; however, preservation of the biological activities of therapeutic allografts during processing remains a challenge. In this study, PURION(R) (MiMedx, Marietta, GA) processed dehydrated human amnion/chorion tissue allografts (dHACM, EpiFix(R), MiMedx) were evaluated for the presence of growth factors, interleukins (ILs) and tissue inhibitors of metalloproteinases (TIMPs). Enzyme-linked immunosorbent assays (ELISA) were performed on samples of dHACM and showed quantifiable levels of the following growth factors: platelet-derived growth factor-AA (PDGF-AA), PDGF-BB, transforming growth factor alpha (TGFalpha), TGFbeta1, basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), placental growth factor (PLGF) and granulocyte colony-stimulating factor (GCSF). The ELISA assays also confirmed the presence of IL-4, 6, 8 and 10, and TIMP 1, 2 and 4. Moreover, the relative elution of growth factors into saline from the allograft ranged from 4% to 62%, indicating that there are bound and unbound fractions of these compounds within the allograft. dHACM retained biological activities that cause human dermal fibroblast proliferation and migration of human mesenchymal stem cells (MSCs) in vitro. An in vivo mouse model showed that dHACM when tested in a skin flap model caused mesenchymal progenitor cell recruitment to the site of implantation. The results from both the in vitro and in vivo experiments clearly established that dHACM contains one or more soluble factors capable of stimulating MSC migration and recruitment. In summary, PURION(R) processed dHACM retains its biological activities related to wound healing, including the potential to positively affect four distinct and pivotal physiological processes intimately involved in wound healing: cell proliferation, inflammation, metalloproteinase activity and recruitment of progenitor cells. This suggests a paracrine mechanism of action for dHACM when used for wound healing applications.

Koury, M. J. and M. A. Lichtman (2010). Structure of the marrow and the hematopoietic microenvironment. Williams Hematology. J. T. Prchal, K. Kaushansky, M. A. Lichtman, T. J. Kipps and U. Seligsoh. New York, Mc-Graw Hill.

Kovacic, J. C., et al. (2008). "Safety and efficacy of consecutive cycles of granulocyte-colony stimulating factor, and an intracoronary CD133+ cell infusion in patients with chronic refractory ischemic heart disease: the G-CSF in angina patients with IHD to stimulate neovascularization (GAIN I) trial." Am Heart J 156(5): 954-963.

BACKGROUND: Preclinical studies suggest granulocyte-colony stimulating factor (G-CSF) holds promise for treating ischemic heart disease; however; its clinical safety and efficacy in this setting remain unclear. We elected to evaluate the safety and efficacy of G-CSF administration in patients with refractory "no-option" ischemic heart disease. METHODS: Twenty patients (18 males, 2 females, mean age 62.4 years) were enrolled and underwent baseline cardiac ischemia assessment (CA) (angina questionnaire, exercise stress test [EST], technetium Tc 99m sestamibi and dobutamine-stress echocardiographic imaging). Patients then received open-label G-CSF commencing at 10 microg/kg SC for 5 days, with an EST on days 4 and 6 (to facilitate myocardial cytokine generation and stem cell trafficking). After 3 months, CA and the same regimen of G-CSF+ESTs were repeated but, in addition, leukapheresis and a randomized double-blinded intracoronary infusion of CD133+ or unselected cells were performed. Final CA occurred 3 months thereafter. RESULTS: There were no deaths, but only 16 patients were permitted to complete the study. Eight events fulfilled prespecified "adverse event" criteria, including 4 troponin I-positive events and 2 episodes of thrombocytopenia. Also, frequent minor troponin I-positive events (troponin I<0.9 microg/L) were observed, which did not meet adverse event criteria. The administration of consecutive cycles of G-CSF resulted in stepwise improvements in anginal frequency, EST performance, and Duke treadmill scores (all P<.005). However, from baseline to final follow-up, technetium Tc 99m sestamibi and dobutamine-stress echocardiographic results were unchanged. CONCLUSIONS: Granulocyte-colony stimulating factor administration was associated with improvement in a range of subjective outcomes. However, adverse events were common, and objective measures of cardiac perfusion/ischemia were unchanged.

Krause, D. S., et al. (2001). "Multi-organ, multi-lineage engraftment by a single bone marrow-derived stem cell." Cell 105(3): 369-377.

Purification of rare hematopoietic stem cell(s) (HSC) to homogeneity is required to study their self-renewal, differentiation, phenotype, and homing. Long-term repopulation (LTR) of irradiated hosts and serial transplantation to secondary hosts represent the gold standard for demonstrating self-renewal and differentiation, the defining properties of HSC. We show that rare cells that home to bone marrow can LTR primary and secondary recipients. During the homing, CD34 and SCA-1 expression increases uniquely on cells that home to marrow. These adult bone marrow cells have tremendous differentiative capacity as they can also differentiate into epithelial cells of the liver, lung, GI tract, and skin. This finding may contribute to clinical treatment of genetic disease or tissue repair.

Kucia, M., et al. (2004). "Cells expressing early cardiac markers reside in the bone marrow and are mobilized into the peripheral blood after myocardial infarction." Circ Res 95(12): 1191-1199.

The concept that bone marrow (BM)-derived cells participate in cardiac regeneration remains highly controversial and the identity of the specific cell type(s) involved remains unknown. In this study, we report that the postnatal BM contains a mobile pool of cells that express early cardiac lineage markers (Nkx2.5/Csx, GATA-4, and MEF2C). These cells are present in significant amounts in BM harvested from young mice but their abundance decreases with age; in addition, the responsiveness of these cells to gradients of motomorphogens SDF-1, HGF, and LIF changes with age. FACS analysis, combined with analysis of early cardiac markers at the mRNA and protein levels, revealed that cells expressing these markers reside in the nonadherent, nonhematopoietic CXCR4+/Sca-1+/lin-/CD45- mononuclear cell (MNC) fraction in mice and in the CXCR4+/CD34+/AC133+/CD45- BMMNC fraction in humans. These cells are mobilized into the peripheral blood after myocardial infarction and chemoattracted to the infarcted myocardium in an SDF-1-CXCR4-, HGF-c-Met-, and LIF-LIF-R-dependent manner. To our knowledge, this is the first demonstration that the postnatal BM harbors a nonhematopoietic population of cells that express markers for cardiac differentiation. We propose that these potential cardiac progenitors may account for the myocardial regenerative effects of BM. The present findings provide a novel paradigm that could reconcile current controversies and a rationale for investigating the use of BM-derived cardiac progenitors for myocardial regeneration.

Kucia, M., et al. (2009). Nonhematopoietic stem cells originating within the bone marrow. Hematology: Basic Principles and Practice. R. Hoffman, E. J. J. Benz, S. J. Shattil et al. Philadelphia, PA, Churchill Livingston Elsevier: 231-243.

Kucia, M., et al. (2006). "Cells enriched in markers of neural tissue-committed stem cells reside in the bone marrow and are mobilized into the peripheral blood following stroke." Leukemia 20(1): 18-28.

The concept that bone marrow (BM)-derived cells participate in neural regeneration remains highly controversial and the identity of the specific cell type(s) involved remains unknown. We recently reported that the BM contains a highly mobile population of CXCR4+ cells that express mRNA for various markers of early tissue-committed stem cells (TCSCs), including neural TCSCs. Here, we report that these cells not only express neural lineage markers (beta-III-tubulin, Nestin, NeuN, and GFAP), but more importantly form neurospheres in vitro. These neural TCSCs are present in significant amounts in BM harvested from young mice but their abundance and responsiveness to gradients of motomorphogens, such as SDF-1, HGF, and LIF, decreases with age. FACS analysis, combined with analysis of neural markers at the mRNA and protein levels, revealed that these cells reside in the nonhematopoietic CXCR4+/Sca-1+/lin-/CD45 BM mononuclear cell fraction. Neural TCSCs are mobilized into the peripheral-blood following stroke and chemoattracted to the damaged neural tissue in an SDF-1-CXCR4-, HGF-c-Met-, and LIF-LIF-R-dependent manner. Based on these data, we hypothesize that the postnatal BM harbors a nonhematopoietic population of cells that express markers of neural TCSCs that may account for the beneficial effects of BM-derived cells in neural regeneration.

Kusumanto, Y. H., et al. (2003). "Platelets and granulocytes, in particular the neutrophils, form important compartments for circulating vascular endothelial growth factor." Angiogenesis 6(4): 283-287.

The measurement of circulating vascular endothelial growth factor (VEGF) levels as a prognostic factor will gain increasing relevance in the diagnosis and evaluation of treatment in cancer patients. Angiogenesis is an absolute requirement in tumour growth and metastatic disease. In the present study data are presented which indicate that circulating VEGF mainly resides in peripheral blood cells. In 15 healthy volunteers we demonstrated that approximately 34% of the circulating VEGF resides in platelets and approximately 11% in patients with cancer ( n = 4). An important part namely 58% in healthy volunteers and 69% in patients with cancer of the total circulating VEGF is contained in granulocytes, particular in the neutrophils, as confirmed by fluorescence-activated cell sorting (FACS). Also an increased VEGF level per granulocyte is found in patients with cancer (77 microg VEGF/l) compared with the healthy volunteers (164 microg VEGF/l). In contrast only 2% was present in plasma. The biological significance of platelet- or granulocyte-derived VEGF is not yet known. Liberation of VEGF from these compartments could well be of importance for tumour angiogenesis. Therefore, future studies on the clinical value of circulating VEGF as a prognostic factor in cancer patients should include measurements of VEGF in peripheral blood cells.

LaBarge, M. A. and H. M. Blau (2002). "Biological progression from adult bone marrow to mononucleate muscle stem cell to multinucleate muscle fiber in response to injury." Cell 111(4): 589-601.

Adult bone marrow-derived cells (BMDC) are shown to contribute to muscle tissue in a step-wise biological progression. Following irradiation-induced damage, transplanted GFP-labeled BMDC become satellite cells: membrane-ensheathed mononucleate muscle stem cells. Following a subsequent exercise-induced damage, GFP-labeled multinucleate myofibers are detected. Isolated GFP-labeled satellite cells are heritably myogenic. They express three characteristic muscle markers, are karyotypically diploid, and form clones that can fuse into multinucleate cells in culture or into myofibers after injection into mouse muscles. These results suggest that two temporally distinct injury-related signals first induce BMDC to occupy the muscle stem cell niche and then to help regenerate mature muscle fibers. The stress-induced progression of BMDC to muscle satellite cell to muscle fiber results in a contribution to as many as 3.5% of muscle fibers and is due to developmental plasticity in response to environmental cues.

Lafforgue, P. (2006). "Pathophysiology and natural history of avascular necrosis of bone." Joint Bone Spine 73(5): 500-507.

Avascular necrosis of bone (AVN) occurs as two main variants, local and systemic. Local AVN is usually caused by trauma or microtrauma; examples include primary osteonecrosis of the medial condyle, vertebral osteonecrosis, necrosis after meniscectomy, and osteonecrosis of the mandible or small bones. Systemic AVN manifests as epiphyseal necrosis or bone infarction, which is often multifocal. Little is known about the factors that trigger AVN. One possible mechanism is intraluminal obliteration of blood vessels by microscopic fat emboli, sickle cells, nitrogen bubbles (caisson disease), or focal clotting due to procoagulant abnormalities. Extraluminal obliteration may result from elevated marrow pressure or increased marrow fat. Cytotoxicity and genetic factors may be involved also. Many factors are probably capable of inducing AVN, and combinations of factors may be required, although the final mechanism is always critical ischemia. The natural history of AVN is better understood than the early triggering factors. AVN becomes detectable 1-6 months after exposure to an easily identifiable risk factor such as high-dose glucocorticoid therapy or femoral neck fracture. Later on, AVN is uncommon even when the patient remains exposed to the risk factor. The turning point in the natural history of AVN is subchondral plate fracture, which leads to collapse of the necrotic segment of the epiphysis, usually within the first 2 years. The risk of collapse depends chiefly on the initial size and location of the necrotic segment, which can be determined accurately by magnetic resonance imaging (MRI). This natural history has obvious clinical implications.

Lakshmipathy, U. and C. Verfaillie (2005). "Stem cell plasticity." Blood Rev 19(1): 29-38.

The central dogma in stem cell biology has been that cells isolated from a particular tissue can renew and differentiate into lineages of the tissue it resides in. Several studies have challenged this idea by demonstrating that tissue specific cell have considerable plasticity and can cross-lineage restriction boundary and give rise to cell types of other lineages. However, the lack of a clear definition for plasticity has led to confusion with several reports failing to demonstrate that a single cell can indeed differentiate into multiple lineages at significant levels. Further, differences between results obtained in different labs has cast doubt on some results and several studies still await independent confirmation. In this review, we critically evaluate studies that report stem cell plasticity using three rigid criteria to define stem cell plasticity; differentiation of a single cell into multiple cell lineages, functionality of differentiated cells in vitro and in vivo, robust and persistent engraft of transplanted cells.

LaRue, A. C., et al. (2006). "Hematopoietic origins of fibroblasts: I. In vivo studies of fibroblasts associated with solid tumors." Exp Hematol 34(2): 208-218.

OBJECTIVE: Recent studies have reported that bone marrow cells can give rise to tissue fibroblasts. However, the bone marrow cell(s) that gives rise to fibroblasts has not yet been identified. In the present study, we tested the hypothesis that tissue fibroblasts are derived from hematopoietic stem cells (HSCs) in vivo. METHODS: These studies were conducted using mice whose hematopoiesis had been reconstituted by transplantation of a clonal population of cells derived from a single enhanced green fluorescent protein (EGFP)-positive HSC in conjunction with murine tumor models. RESULTS: When tumors propagated in the transplanted mice were evaluated for the presence of EGFP(+) HSC-derived cells, two prominent populations of EGFP(+) cells were found. The first were determined to be fibroblasts within the tumor stromal capsule, a subset of which expressed type I collagen mRNA and alpha-smooth muscle actin. The second population was a perivascular cell associated with the CD31(+) tumor blood vessels. CONCLUSION: These in vivo findings establish an HSC origin of fibroblasts.

Leal, L. (2007). Adult stem cell treatment strategy for jones fracture and nonunion of the proximal fifth metatarsal. New York-Presbyterian Healthcare System

North Bergen, NJ: 2.

Lee, K., et al. (2009). "Cell therapy for bone regeneration--bench to bedside." J Biomed Mater Res B Appl Biomater 89(1): 252-263.

The concept of bone tissue engineering, which began in the early 1980s, has seen tremendous growth in the numbers of research studies. One of the key areas of research has been in the field of mesenchymal stem cells, where the challenge is to produce the perfect tissue-engineered bone construct. This practical review summarizes basic and applied state-of-the-art research in the area of mesenchymal stem cells, and highlights the important translational research that has already been initiated. The topics that will be covered include the sources of stem cells in use, scaffolds, gene therapy, clinical applications in nonunions, tumors, osteonecrosis, revision arthroplasties, and spine fusion. Although significant challenges remain, there exists an exceptional opportunity to translate basic research in mesenchymal stem cell technologies into viable clinical treatments for bone regeneration.

Leri, A., et al. (2005). "Cardiac stem cells and mechanisms of myocardial regeneration." Physiol Rev 85(4): 1373-1416.

This review discusses current understanding of the role that endogenous and exogenous progenitor cells may have in the treatment of the diseased heart. In the last several years, a major effort has been made in an attempt to identify immature cells capable of differentiating into cell lineages different from the organ of origin to be employed for the regeneration of the damaged heart. Embryonic stem cells (ESCs) and bone marrow-derived cells (BMCs) have been extensively studied and characterized, and dramatic advances have been made in the clinical application of BMCs in heart failure of ischemic and nonischemic origin. However, a controversy exists concerning the ability of BMCs to acquire cardiac cell lineages and reconstitute the myocardium lost after infarction. The recognition that the adult heart possesses a stem cell compartment that can regenerate myocytes and coronary vessels has raised the unique possibility to rebuild dead myocardium after infarction, to repopulate the hypertrophic decompensated heart with new better functioning myocytes and vascular structures, and, perhaps, to reverse ventricular dilation and wall thinning. Cardiac stem cells may become the most important cell for cardiac repair.

Leri, A., et al. (2004). "Some like it plastic." Circ Res 94(2): 132-134.

Li, L. and H. Clevers (2010). "Coexistence of quiescent and active adult stem cells in mammals." Science 327(5965): 542-545.

Adult stem cells are crucial for physiological tissue renewal and regeneration after injury. Prevailing models assume the existence of a single quiescent population of stem cells residing in a specialized niche of a given tissue. Emerging evidence indicates that both quiescent (out of cell cycle and in a lower metabolic state) and active (in cell cycle and not able to retain DNA labels) stem cell subpopulations may coexist in several tissues, in separate yet adjoining locations. Here, we summarize these findings and propose that quiescent and active stem cell populations have separate but cooperative functional roles.

Li, Z. Q., et al. (2007). "The clinical study of autologous peripheral blood stem cell transplantation by intracoronary infusion in patients with acute myocardial infarction (AMI)." Int J Cardiol 115(1): 52-56.

PURPOSE: To investigate the effects and safety of autologous peripheral blood stem cell (PBSCs) transplantation by intracoronary infusion in patients with acute myocardial infarction (AMI). METHODS: 70 patients with AMI were allocated to two groups, one was PBSCs transplantation group (n=35) that received optimal post-infarction medical treatment (standard drug and coronary artery intervention therapy) and intracoronary transplantation of PBSCs; the other was control group (n=35) that received optimum post-infarction medical treatment (standard drug and coronary artery intervention therapy). The PBSCs transplantation group received granulocyte colony-stimulating factor (G-CSF: Filgrastim, 300 microg) with the dose of 300-600 microg/day to mobilize the stem cell, and the duration of administration G-CSF was 5 days. On the sixth day, PBSCs were separated by Baxter CS 3000 blood cell separator into suspend liquid 57 ml. Then, the suspend liquid was transferred into the infarct-related artery (IRA) by occluding the over-the-wire balloon and infusing artery through balloon center lumen. In the process of the mobilization, separation and intracoronary infusion of PBSCs, the complications have been investigated. Changes in left ventricular function were assessed at 6-month follow-up. RESULTS: 35 cases had finished follow-up in the treated group, while 23 cases in control group. After 6 months, within the treated group, there was a significant improvement in global left ventricular function ejection fraction (EF) from a baseline of 50.0+/-8.2% to 57.1+/-7.8% (P<0.0001), wall motion score index (WMSI) from 1.219+/-0.190 to 1.101+/-0.118 (P<0.0001), left end-systolic volume (ESV) from 63.8+/-23.9 ml to 52.6+/-20.3 ml (P=0.01) and left end-diastolic volume (EDV) from 134.2+/-36.7 ml to 119.2+/-30.3 ml (P=0.07); in the control group, there was no significant improvement in EF, WISM, EDV and ESV (P=0.490, 0.259, 0.117, 0.395). After 6-month follow-up, according to treatment group vs. control group, there was a significant improvement in EF from 57.1+/-7.8 to 52.6+/-5.7 (P=0.041) and WISM from 1.101+/-0.118 to 1.184+/-0.138 (P=0.034). There were a total of 25 cases with complications during the mobilization, separating and infusion of PBSC. The incidence of complications relating to mobilization was 37.1% (13/35), relating to separating was 14.3% (5/35) and relating to intracoronary infusion was 20.0% (7/35). No death was observed. CONCLUSION: Autologous PBSCs transplantation by intracoronary infusion is feasible and safe, and it can improve left ventricular function in the 6-month follow-up.

Lieberman, J. R., et al. (2002). "The role of growth factors in the repair of bone. Biology and clinical applications." J Bone Joint Surg Am 84-A(6): 1032-1044.

Lin, G., et al. (2008). "Defining stem and progenitor cells within adipose tissue." Stem Cells Dev 17(6): 1053-1063.

Adipose tissue-derived stem cells (ADSC) are routinely isolated from the stromal vascular fraction (SVF) of homogenized adipose tissue. Freshly isolated ADSC display surface markers that differ from those of cultured ADSC, but both cell preparations are capable of multipotential differentiation. Recent studies have inferred that these progenitors may reside in a perivascular location where they appeared to coexpress CD34 and smooth muscle actin (alpha-SMA) but not CD31. However, these studies provided only limited histological evidence to support such assertions. In the present study, we employed immunohistochemistry and immunofluorescence to define more precisely the location of ADSC within human adipose tissue. Our results show that alpha-SMA and CD31 localized within smooth muscle and endothelial cells, respectively, in all blood vessels examined. CD34 localized to both the intima (endothelium) and adventitia neither of which expressed alpha-SMA. The niche marker Wnt5a was confined exclusively to the vascular wall within mural smooth muscle cells. Surprisingly, the widely accepted mesenchymal stem cell marker STRO-1 was expressed exclusively in the endothelium of capillaries and arterioles but not in the endothelium of arteries. The embryonic stem cell marker SSEA1 localized to a pericytic location in capillaries and in certain smooth muscle cells of arterioles. Cells expressing the embryonic stem cell markers telomerase and OCT4 were rare and observed only in capillaries. Based on these findings and evidence gathered from the existing literature, we propose that ADSC are vascular precursor (stem) cells at various stages of differentiation. In their native tissue, ADSC at early stages of differentiation can differentiate into tissue-specific cells such as adipocytes. Isolated, ADSC can be induced to differentiate into additional cell types such as osteoblasts and chondrocytes.

Liu, P. K., et al. (2009). "Brain probles for MRI of de novo neural progenitor cells in live brains after global cerebral ischemia." Journal of Cerebral Blood Flow & Metabolism 29: S376.

Lo Celso, C. and D. T. Scadden (2011). "The haematopoietic stem cell niche at a glance." J Cell Sci 124(Pt 21): 3529-3535.

Long, F. (2011). "Building strong bones: molecular regulation of the osteoblast lineage." Nat Rev Mol Cell Biol 13(1): 27-38.

The past 15 years have witnessed tremendous progress in the molecular understanding of osteoblasts, the main bone-forming cells in the vertebrate skeleton. In particular, all of the major developmental signals (including WNT and Notch signalling), along with an increasing number of transcription factors (such as RUNX2 and osterix), have been shown to regulate the differentiation and/or function of osteoblasts. As evidence indicates that osteoblasts may also regulate the behaviour of other cell types, a clear understanding of the molecular identity and regulation of osteoblasts is important beyond the field of bone biology.

Long, M. A., et al. (2005). "Circulating myogenic progenitors and muscle repair." Semin Cell Dev Biol 16(4-5): 632-640.

The capability of bone marrow derived cells to contribute to numerous peripheral tissues may hold tremendous promise for the field of regenerative medicine. In the context of skeletal muscle disease in particular, the ability of these cells to reach sites of damage through the circulation would overcome some key limitations of current cell therapy approaches. In muscle however, this non-classical repair process takes place at an exceedingly low frequency and fails to yield any measurable functional improvement. Recent advances regarding the cell types or mechanisms involved in this phenomenon may now provide direction for strategies aimed at increasing its efficiency to therapeutic levels.

Long, M. W., et al. (1995). "Regulation of human bone marrow-derived osteoprogenitor cells by osteogenic growth factors." J Clin Invest 95(2): 881-887.

Human bone marrow contains a distinct cell population that expresses bone proteins and responds to transforming growth factor beta 1 (TGF-beta), but not to hematopoietic growth factors (Long, M. W., J. L. Williams, and K. G. Mann. 1990. J. Clin. Invest. 86:1387-1395). We now report the isolation, characterization, and growth factor responsiveness of these precursors to human osteoblasts and the identification of a human osteoprogenitor cell. Immunological separation of human bone marrow nonadherent low-density (NALD) cells results in a marked enrichment of cells that express osteocalcin, osteonectin, and bone alkaline phosphatase. Flow cytometric analyses show that distinct cell subpopulations exist among these isolated cells. The majority of the bone antigen-positive cells are approximately the size of a lymphocyte, whereas other, less frequent antibody-separated subpopulations consist of osteoblast-like cells and osteoprogenitor cells. In serum-free cultures, TGF-beta stimulates the small, antigen-positive cells to become osteoblast-like, as these cells both increase in size, and express increased levels of osteocalcin and alkaline phosphatase. Antibody-separated cells also contain a separate population of clonal progenitor cells that form colonies of osteoblast-like cells when cultured in serum-free, semi-solid media. Two types of human osteoprogenitor cells are observed: a colony-forming cell (CFC) that generates several hundred bone antigen-positive cells, and a more mature cluster-forming cell that has a lesser proliferative potential and thus generates clusters of 20-50 antigen-positive cells. Osteopoietic colony-forming cells and cluster-forming cells have an obligate but differential requirement for osteogenic growth factors. The CFCs respond to TGF-beta, basic fibroblast growth factor (bFGF), bone morphogenic protein-2 (BMP-2), and 1, 25-dihydroxy vitamin D3 (1,25-OH D3). In contrast to the colony-forming cells, cluster-forming cells are regulated predominantly by 1,25-OH D3 and TGF-beta, but fail to respond to bFGF. We conclude that human bone marrow contains a nonhematogenous, heterogeneous population of bone precursor cells among which exists a population of proliferating osteoprogenitor cells. Further characterization of these bone precursor cell populations should yield important information on their role in osteogenesis in both health and disease.

Long, M. W., et al. (1990). "Expression of human bone-related proteins in the hematopoietic microenvironment." J Clin Invest 86(5): 1387-1395.

Given the intimate relationship between bone and bone marrow, we hypothesized that the human bone marrow may function as a source (or reservoir) of bone-forming progenitor cells. We observed a population of cells within the bone marrow which produce bone-specific or bone-related proteins. The production of these proteins was developmentally regulated in human long-term bone marrow cell cultures; the bone protein-producing cells (BPPC) are observed under serum-free, short-term culture conditions, respond to bone-related and not hematopoietic growth factors, and are derived from a population of low-density, nonadherent, My10-negative (or low My10 density), marrow cells (My10 is an antigen found on most hematopoietic progenitor cells). Cultivation of marrow-derived BPPC in secondary, serum-containing cultures results in their differentiation into osteoblastlike cells. At this stage of development, BPPC produce an extracellular matrix which incorporates both bone-related proteins and radiolabeled calcium. Human bone marrow BPPC thus represent a newly described cell phenotype important to both bone and hematopoietic cell biology.

Lu, D., et al. (2011). "Comparison of bone marrow mesenchymal stem cells with bone marrow-derived mononuclear cells for treatment of diabetic critical limb ischemia and foot ulcer: a double-blind, randomized, controlled trial." Diabetes Res Clin Pract 92(1): 26-36.

AIMS: To identify better cells for the treatment of diabetic critical limb ischemia (CLI) and foot ulcer in a pilot trial. METHODS: Under ordinary treatment, the limbs of 41 type 2 diabetic patients with bilateral CLI and foot ulcer were injected intramuscularly with bone marrow mesenchymal stem cells (BMMSCs), bone marrow-derived mononuclear cells (BMMNCs), or normal saline (NS). RESULTS: The ulcer healing rate of the BMMSC group was significantly higher than that of BMMNCs at 6 weeks after injection (P=0.022), and reached 100% 4 weeks earlier than BMMNC group. After 24 weeks of follow-up, the improvements in limb perfusion induced by the BMMSCs transplantation were more significant than those by BMMNCs in terms of painless walking time (P=0.040), ankle-brachial index (ABI) (P=0.017), transcutaneous oxygen pressure (TcO(2)) (P=0.001), and magnetic resonance angiography (MRA) analysis (P=0.018). There was no significant difference between the groups in terms of pain relief and amputation and there was no serious adverse events related to both cell injections. CONCLUSIONS: BMMSCs therapy may be better tolerated and more effective than BMMNCs for increasing lower limb perfusion and promoting foot ulcer healing in diabetic patients with CLI.

Ludwig, S. C., et al. (2000). "Osteoinductive bone graft substitutes." Eur Spine J 9 Suppl 1: S119-125.

This review will summarize the major efforts currently underway to develop osteoinductive bone graft substitutes for minimally invasive spine fusions. The primary categories of substitute include purified bone growth factors, recombinant bone growth factors, and growth factors delivered by gene therapy approaches. Clinical trials are underway for the purified and recombinant bone growth factors and pre-clinical studies have yielded promising results for a variety of gene therapy techniques for generating bone.

Luis, T. C., et al. (2011). "Canonical wnt signaling regulates hematopoiesis in a dosage-dependent fashion." Cell Stem Cell 9(4): 345-356.

Canonical Wnt signaling has been implicated in the regulation of hematopoiesis. By employing a Wnt-reporter mouse, we observed that Wnt signaling is differentially activated during hematopoiesis, suggesting an important regulatory role for specific Wnt signaling levels. To investigate whether canonical Wnt signaling regulates hematopoiesis in a dosage-dependent fashion, we analyzed the effect of different mutations in the Adenomatous polyposis coli gene (Apc), a negative modulator of the canonical Wnt pathway. By combining different targeted hypomorphic alleles and a conditional deletion allele of Apc, a gradient of five different Wnt signaling levels was obtained in vivo. We here show that different, lineage-specific Wnt dosages regulate hematopoietic stem cells (HSCs), myeloid precursors, and T lymphoid precursors during hematopoiesis. Differential, lineage-specific optimal Wnt dosages provide a unifying concept that explains the differences reported among inducible gain-of-function approaches, leading to either HSC expansion or depletion of the HSC pool.

Lukowizc, T. v., et al. (2005). "BNP as a marker of diastolic dysfunction in the general population: Importance of left ventricular hypertrophy." The European Journal of Heart Failure 7: 525-531.

BNP is a marker of systolic left ventricular dysfunction (LVSD) and heart failure. To assess BNP for the detection of diastolic dysfunction

in the general population, we examined 1678 subjects within an age- and sex-stratified survey (MONICA Augsburg). BNP was measured

using a commercially available RIA (Shionogi).

BNP increased in subjects with diastolic dysfunction (mean 20.3F4.7 pg/ml vs. control 9.6F0.5 pg/ml, pb0.001), but to a lesser

extent than in subjects with LV hypertrophy (LVH, mean 37.3F49.1 pg/ml, pb0.001 vs. control) or LVSD (mean 76.2F23.2 pg/ml,

pb0.001 vs. control). Individuals with sole diastolic abnormality displayed BNP concentrations at the control level (mean 9.7F1.7 pg/

ml). In univariate analysis, age, BMI, systolic blood pressure, left atrial size, LV mass index, diastolic dysfunction and EF displayed a

significant correlation with BNP ( pb0.001). However, LV mass index displaced diastolic dysfunction as a significant predictor of BNP

in multivariate analysis. Upon ROC analysis, sensitivity and specificity for the detection of diastolic dysfunction by BNP were only

61% and 55%, respectively. Nevertheless, a normal BNP test virtually excluded the presence of diastolic dysfunction and concomitant

LVH (NPV 99.9%).

Increased BNP concentrations in subjects with diastolic dysfunction are strongly related to LVH. Population-wide screening for diastolic

dysfunction with BNP cannot be recommended although a normal BNP test usually excludes diastolic dysfunction and LV hypertrophy.

Lysaght, T. and A. V. Campbell (2011). "Regulating autologous adult stem cells: the FDA steps up." Cell Stem Cell 9(5): 393-396.

The Food and Drug Administration (FDA) has sought an injunction to prevent a US-based company from offering an autologous adult stem cell treatment for musculoskeletal and spinal injuries. Given the alarming number of clinics promoting stem-cell-based interventions, the outcome of this case could have wide-ranging implications.

Maes, C., et al. (2010). "Osteoblast precursors, but not mature osteoblasts, move into developing and fractured bones along with invading blood vessels." Dev Cell 19(2): 329-344.

During endochondral bone development, the first osteoblasts differentiate in the perichondrium surrounding avascular cartilaginous rudiments; the source of trabecular osteoblasts inside the later bone is, however, unknown. Here, we generated tamoxifen-inducible transgenic mice bred to Rosa26R-LacZ reporter mice to follow the fates of stage-selective subsets of osteoblast lineage cells. Pulse-chase studies showed that osterix-expressing osteoblast precursors, labeled in the perichondrium prior to vascular invasion of the cartilage, give rise to trabecular osteoblasts, osteocytes, and stromal cells inside the developing bone. Throughout the translocation, some precursors were found to intimately associate with invading blood vessels, in pericyte-like fashion. A similar coinvasion occurs during endochondral healing of bone fractures. In contrast, perichondrial mature osteoblasts did not exhibit perivascular localization and remained in the outer cortex of developing bones. These findings reveal the specific involvement of immature osteoblast precursors in the coupled vascular and osteogenic transformation essential to endochondral bone development and repair.

Mandelbaum, B. and D. Waddell (2005). "Etiology and pathophysiology of osteoarthritis." Orthopedics 28(2 Suppl): s207-214.

Acute or chronic insult, including normal wear and tear, age, obesity, and joint injury, may initiate an imbalance between matrix synthesis and matrix degradation in healthy cartilage that promotes chondral loss and prevents cartilage self-repair. The structure of healthy cartilage and the pathophysiological mechanisms of its degradation are described, followed by descriptions of endogenous and exogenous factors believed to be involved in the progressive course of osteoarthritis. Studies cited include research from the community of sports medicine.

Mankin, H. J. (1992). "Nontraumatic Necrosis of Bone (Osteonecrosis)." New England Journal of Medicine 326(22): 1473-1479.

Margulies, L. A., et al. (2006). Method and apparatus for monitoring the autonomic nervous system, Google Patents.

Marker, D. R., et al. (2008). "Do modern techniques improve core decompression outcomes for hip osteonecrosis?" Clin Orthop Relat Res 466: 1093-1103.

Martino, G., et al. (2011). "Therapeutic stem cell plasticity orchestrates tissue plasticity." Brain 134(Pt 6): 1585-1587.

Marx, R. E., et al. (1998). "Platelet-rich plasma: Growth factor enhancement for bone grafts." Oral Surg Oral Med Oral Pathol Oral Radiol Endod 85(6): 638-646.

Platelet-rich plasma is an autologous source of platelet-derived growth factor and transforming growth factor beta that is obtained by sequestering and concentrating platelets by gradient density centrifugation. This technique produced a concentration of human platelets of 338% and identified platelet-derived growth factor and transforming growth factor beta within them. Monoclonal antibody assessment of cancellous cellular marrow grafts demonstrated cells that were capable of responding to the growth factors by bearing cell membrane receptors. The additional amounts of these growth factors obtained by adding platelet-rich plasma to grafts evidenced a radiographic maturation rate 1.62 to 2.16 times that of grafts without platelet-rich plasma. As assessed by histomorphometry, there was also a greater bone density in grafts in which platelet-rich plasma was added (74.0% +/- 11%) than in grafts in which platelet-rich plasma was not added (55.1% +/- 8%; p = 0.005).

Marx, R. E. and D. B. Harrell (2012). "Translational research: The CD34+ cell is crucial for large-volume bone regeneration from the milieu of bone marrow progenitor cells in craniomandibular reconstruction." Oral Craniofac Tissue Eng 2(4): 263-271.

Purpose: This study investigated the role of the bone marrow–derived CD34+ cell in a milieu of osteoprogenitor cells, bone marrow plasma cell adhesion molecules, recombinant human bone morphogenetic protein (rhBMP), and a matrix of crushed cancellous allogeneic bone in the clinical regeneration of functionally useful bone in craniomandibular reconstructions. The history and current concepts of bone marrow hematopoietic stem cells and mesenchymal stem cells are reviewed as they relate to bone regeneration in large continuity defects of the mandible. Materials and Methods: Patients with 6- to 8-cm continuity defects of the mandible with retained proximal and distal segments were randomized into two groups. Group A received an in situ tissue-engineered graft containing 54 ± 38 CD34+ cells/mL along with 54 ± 38 CD44+, CD90+, and CD105+ cells/mL together with rhBMP-2 in an absorbable collagen sponge (1 mg/cm of defect) and crushed cancellous allogeneic bone. Group B received the same graft, except the CD34+ cell concentration was 1,012 ± 752 cells/mL. The results were analyzed clinically, radiographic bone density was measured in Hounsfield units (HU), and specimens were analyzed histomorphometrically. Results: Forty patients participated (22 men and 12 women; mean age, 57 years). Eight of 20 group A patients (40%) achieved the primary endpoint of mature bone regeneration, whereas all 20 group B patients (100%) achieved the primary endpoint. CD34+ cell counts above 200/mL were associated with achievement of the primary endpoint. Bone density was lower in group A (424 ± 115 HU) than in group B (731 ± 98 HU). Group A bone showed a mean trabecular bone area of 36% ± 10%, versus 67% ± 13% for group B. Conclusions: The CD34+ cell functions as a central signaling cell to mesenchymal stem cells and osteoprogenitor cells in bone regeneration. The mechanism of bone marrow–supported grafts requires a complete milieu to regenerate large quantities of functionally useful bone. CD34+ cell counts in a concentration of at least 200/mL in composite grafts are directly correlated to clinically successful bone regeneration. Oral Craniofac Tissue Eng 2012;2:263–271. doi: 10.11607/octe.0059

Massberg, S., et al. (2006). "Platelets secrete stromal cell-derived factor 1alpha and recruit bone marrow-derived progenitor cells to arterial thrombi in vivo." J Exp Med 203(5): 1221-1233.

The accumulation of smooth muscle and endothelial cells is essential for remodeling and repair of injured blood vessel walls. Bone marrow-derived progenitor cells have been implicated in vascular repair and remodeling; however, the mechanisms underlying their recruitment to the site of injury remain elusive. Here, using real-time in vivo fluorescence microscopy, we show that platelets provide the critical signal that recruits CD34+ bone marrow cells and c-Kit+ Sca-1+ Lin- bone marrow-derived progenitor cells to sites of vascular injury. Correspondingly, specific inhibition of platelet adhesion virtually abrogated the accumulation of both CD34+ and c-Kit+ Sca-1+ Lin- bone marrow-derived progenitor cells at sites of endothelial disruption. Binding of bone marrow cells to platelets involves both P-selectin and GPIIb integrin on platelets. Unexpectedly, we found that activated platelets secrete the chemokine SDF-1alpha, thereby supporting further primary adhesion and migration of progenitor cells. These findings establish the platelet as a major player in the initiation of vascular remodeling, a process of fundamental importance for vascular repair and pathological remodeling after vascular injury.

Matsumoto, T., et al. (2006). "Therapeutic potential of vasculogenesis and osteogenesis promoted by peripheral blood CD34-positive cells for functional bone healing." Am J Pathol 169(4): 1440-1457.

Failures in fracture healing are mainly caused by a lack of vascularization. Adult human circulating CD34+ cells, an endothelial/hematopoietic progenitor-enriched cell population, have been reported to differentiate into osteoblasts in vitro; however, the therapeutic potential of CD34+ cells for fracture healing is still unclear. Therefore, we performed a series of experiments to test our hypothesis that functional fracture healing is supported by vasculogenesis and osteogenesis via regenerative plasticity of CD34+ cells. Peripheral blood CD34+ cells, isolated from total mononuclear cells of adult human volunteers, showed gene expression of osteocalcin in 4 of 20 freshly isolated cells by single cell reverse transcriptase-polymerase chain reaction analysis. Phosphate-buffered saline, mononuclear cells, or CD34+ cells were intravenously transplanted after producing nonhealing femoral fractures in nude rats. Reverse transcriptase-polymerase chain reaction and immunohistochemical staining at the peri-fracture site demonstrated molecular and histological expression of human-specific markers for endothelial cells and osteoblasts at week 2. Functional bone healing assessed by biomechanical as well as radiological and histological examinations was significantly enhanced by CD34+ cell transplantation compared with the other groups. Our data suggest circulating human CD34+ cells have therapeutic potential to promote an environment conducive to neovascularization and osteogenesis in damaged skeletal tissue, allowing the complete healing of fractures.

Matsumoto, T., et al. (2008). "Circulating endothelial/skeletal progenitor cells for bone regeneration and healing." Bone 43(3): 434-439.

An emerging strategy in the regeneration and repair of bone is to use stem cells, including bone marrow mesenchymal stem cells, which are the most investigated and reliable source for tissue engineering, as well as circulating skeletal stem/progenitor cells, which are receiving abundant attention in regenerative medicine due to their ease of isolation and high osteogenic potential. Because failures in fracture healing are largely due to poor vascularization among many environmental factors, we highlight the first proof-of-principle experiments that elucidated the collaborative multi-lineage differentiation of circulating CD34 positive cells - a cell-enriched population of endothelial/hematopoietic progenitor cells - into not only endothelial cells but also osteoblasts. These cells develop a favorable environment for fracture healing via vasculogenesis/angiogenesis and osteogenesis, ultimately leading to functional recovery from fracture. This review will also highlight current concepts of circulating stem/progenitor cell-based therapy and their potential application for bone repair.

Matsumoto, T., et al. (2008). "Fracture induced mobilization and incorporation of bone marrow-derived endothelial progenitor cells for bone healing." J Cell Physiol 215(1): 234-242.

We recently reported that systemic administration of peripheral blood (PB) CD34+ cells, an endothelial progenitor cell (EPC)-enriched population, contributed to fracture healing via vasculogenesis/angiogenesis. However, pathophysiological role of EPCs in fracture healing process has not been fully clarified. Therefore, we investigated the hypothesis whether mobilization and incorporation of bone marrow (BM)-derived EPCs may play a pivotal role in appropriate fracture healing. Serial examinations of Laser doppler perfusion imaging and histological capillary density revealed that neovascularization activity at the fracture site peaked at day 7 post-fracture, the early phase of endochondral ossifification. Fluorescence-activated cell sorting (FACS) analysis demonstrated that the frequency of BM cKit+Sca1+Lineage- (Lin-) cells and PB Sca1+Lin- cells, which are EPC-enriched fractions, significantly increased post-fracture. The Sca1+ EPC-derived vasuculogenesis at the fracture site was confirmed by double immunohistochemistry for CD31 and Sca1. BM transplantation from transgenic donors expressing LacZ transcriptionally regulated by endothelial cell-specific Tie-2 promoter into wild type also provided direct evidence that EPCs contributing to enhanced neovascularization at the fracture site were specifically derived from BM. Animal model of systemic administration of PB Sca1+Lin- Green Fluorescent Protein (GFP)+ cells further confirmed incorporation of the mobilized EPCs into the fracture site for fracture healing. These findings indicate that fracture may induce mobilization of EPCs from BM to PB and recruitment of the mobilized EPCs into fracture sites, thereby augment neovascularization during the process of bone healing. EPCs may play an essential role in fracture healing by promoting a favorable environment through neovascularization in damaged skeletal tissue.

McCulloch, E. A. and J. E. Till (1960). "The radiation sensitivity of normal mouse bone marrow cells, determined by quantitative marrow transplantation into irradiated mice." Radiat Res 13: 115-125.

McKay, W. F., et al. (2007). "A comprehensive clinical review of recombinant human bone morphogenetic protein-2 (INFUSE Bone Graft)." Int Orthop 31(6): 729-734.

The combination of recombinant human bone morphogenetic protein-2 (rhBMP-2) on an absorbable collagen sponge (ACS) carrier has been shown to induce bone formation in a number of preclinical and clinical investigations. In 2002, rhBMP-2/ACS at a 1.5-mg/cc concentration (INFUSE Bone Graft, Medtronic Spinal and Biologics, Memphis, TN) was FDA-approved as an autograft replacement for certain interbody spinal fusion procedures. In 2004, INFUSE Bone Graft was approved for open tibial fractures with an intermedullary (IM) nail fixation. Most recently, in March 2007, INFUSE Bone Graft was approved as an alternative to autogenous bone grafts for sinus augmentations, and for localised alveolar ridge augmentations for defects associated with extraction sockets. The culmination of extensive preclinical and clinical research and three FDA approvals makes rhBMP-2 one of the most studied, published and significant advances in orthopaedics. This review article summarises a number of clinical findings of rhBMP-2/ACS, including the FDA-approved investigational device exemption (IDE) studies used in gaining the aforementioned approvals.

McLain, R. F., et al. (2005). "Aspiration of osteoprogenitor cells for augmenting spinal fusion: comparison of progenitor cell concentrations from the vertebral body and iliac crest." J Bone Joint Surg Am 87(12): 2655-2661.

BACKGROUND: Successful arthrodesis in challenging clinical scenarios is facilitated when the site is augmented with autograft bone. The iliac crest has long been the preferred source of autograft material, but graft harvest is associated with frequent complications and pain. Connective tissue progenitor cells aspirated from the iliac crest and concentrated with allograft matrix and demineralized bone matrix provide a promising alternative to traditional autograft harvest. The vertebral body, an even larger reservoir of myeloproliferative cells, should provide progenitor cell concentrations similar to those of the iliac crest. METHODS: Twenty-one adults (eleven men and ten women with a mean age of 59 +/- 14 years) undergoing posterior lumbar arthrodesis and pedicle screw instrumentation underwent transpedicular aspiration of connective tissue progenitor cells. Aspirates were obtained from two depths within the vertebral body and were quantified relative to matched, bilateral aspirates from the iliac crest that were obtained from the same patient at the same time. Histochemical analysis was used to determine the prevalence of vertebral progenitor cells relative to the depth of aspiration, the vertebral level, age, and gender, as compared with the iliac crest standard. The cell count, progenitor cell concentration (cells/cc marrow), and progenitor cell prevalence (cells/million cells) were calculated. RESULTS: Aspirates of vertebral marrow demonstrated comparable or greater concentrations of progenitor cells compared with matched controls from the iliac crest. Progenitor cell concentrations were consistently higher than matched controls from the iliac crest (p = 0.05). The concentration of osteogenic progenitor cells was, on the average, 71% higher in the vertebral aspirates than in the paired iliac crest samples (p = 0.05). With the numbers available, there were no significant differences relative to vertebral body level, the side aspirated, the depth of aspiration, or gender. An age-related decline in cellularity was suggested for the iliac crest aspirates. CONCLUSIONS: The vertebral body is a suitable site for aspiration of bone marrow for graft augmentation during spinal arthrodesis.

Miao, D., et al. (2004). "Megakaryocyte-bone marrow stromal cell aggregates demonstrate increased colony formation and alkaline phosphatase expression in vitro." Tissue Eng 10(5-6): 807-817.

Bone marrow stromal cells (BMSCs) possess certain stem celllike properties and can differentiate to adopt a number of mesenchymal phenotypes. BMSCs are usually investigated in vitro as homogeneous single-cell suspensions; however, these preparations lose much of their osteogenic capacity. Using the fibroblastic colony-forming unit assay, we have compared the proliferation and capacity to express alkaline phosphatase of BMSC-containing aggregates of bone marrow cells with single-cell suspensions of bone marrow cells from the same source. Aggregates were separated from single cells by density gradient centrifugation or cell sieving. The aggregate and single-cell preparations gave rise to similar numbers of colonies; however, the colonies produced by the aggregates were larger and expressed higher levels of alkaline phosphatase. When the aggregates were dissociated, colonies still formed; however, they expressed negligible levels of alkaline phosphatase. Immunomagnetic selection and immunofluorescent staining for CD61, N-methyl-D-aspartate (NMDA) receptor subunit 1, and acetylcholinesterase showed that the majority of the aggregates giving rise to osteoblastic colonies contained megakaryocytes. These data demonstrate that removing BMSCs from their normal environment reduces their osteoblastic capacity and that to achieve their maximal differentiation, BMSCs require direct physical contact with accessory cells such as megakaryocytes. These findings may be of direct relevance to the use of BMSCs for tissue-engineering purposes.

Middleton, J., et al. (2002). "Leukocyte extravasation: chemokine transport and presentation by the endothelium." Blood 100(12): 3853-3860.

At sites of inflammation and in normal immune surveillance, chemokines direct leukocyte migration across the endothelium. Many cell types that are extravascular can produce chemokines, and for these mediators to directly elicit leukocyte migration from the blood, they would need to reach the luminal surface of the endothelium. This article reviews the evidence that endothelial cells are active in transcytosing chemokines to their luminal surfaces, where they are presented to leukocytes. The endothelial binding sites that transport and present chemokines include glycosaminoglycans (GAGs) and possibly the Duffy antigen/receptor for chemokines (DARC). The binding residues on chemokines that interact with GAGs are discussed, as are the carbohydrate structures on GAGs that bind these cytokines. The expression of particular GAG structures by endothelial cells may lend selectivity to the type of chemokine presented in a given tissue, thereby contributing to selective leukocyte recruitment. At the luminal surface of the endothelium, chemokines are preferentially presented to blood leukocytes on the tips of microvillous processes. Similarly, certain adhesion molecules and chemokine receptors are also preferentially distributed on leukocyte and endothelial microvilli, and evidence suggests an important role for these structures in creating the necessary surface topography for leukocyte migration. Finally, the mechanisms of chemokine transcytosis and presentation by endothelial cells are incorporated into the current model of chemokine-driven leukocyte extravasation.

Mifune, Y., et al. (2008). "Local delivery of granulocyte colony stimulating factor-mobilized CD34-positive progenitor cells using bioscaffold for modality of unhealing bone fracture." Stem Cells 26(6): 1395-1405.

We recently reported that i.v. transplantation of adult human circulating CD34+ cells, an endothelial/hematopoietic progenitor-enriched cell population, contributes to fracture healing through the enhancement of vasculogenesis and osteogenesis. However, the scarcity of CD34+ cells in the adult human is a critical issue for the future clinical application of this method. To overcome this issue, we assessed in vitro and in vivo capacity of granulocyte colony-stimulating factor-mobilized peripheral blood (GM-PB) human CD34+ cells for vasculogenesis and osteogenesis. First, we confirmed the differentiation capability of GM-PB CD34+ cells into osteoblasts in vitro. Second, local transplantation of GM-PB CD34+ cells on atelocollagen scaffold was performed in nude rats in a model of unhealing fractures. Immunostaining for human leukocyte antigen-ABC of tissue samples 1 week after fracture and cell therapy showed the superior incorporation after local transplantation compared with systemic infusion. Third, the effects of local transplantation of 10(5) (Hi), 10(4) (Mid), or 10(3) (Lo) doses of GM-PB CD34+ cells or phosphate-buffered saline (PBS) on fracture healing were compared. Extrinsic vasculogenic and osteogenic differentiation of GM-PB CD34+ cells, enhancement of the intrinsic angio-osteogenesis by recipient cells, augmentation of blood flow recovery at the fracture sites, and radiological and histological confirmation of fracture healing were observed only in the Hi and Mid groups but not in the Lo and PBS groups. These results strongly suggest that local transplantation of GM-PB CD34+ cells with atelocollagen scaffold is a feasible strategy for therapeutic vasculogenesis and osteogenesis needed for fracture healing. Disclosure of potential conflicts of interest is found at the end of this article.

Mirabet, V., et al. (2011). "Viable hematopoietic progenitor cells in frozen femoral heads from living donors for orthopedic surgery." Transfusion 51(2): 443-444.

Modder, U. I. and S. Khosla (2008). "Skeletal stem/osteoprogenitor cells: current concepts, alternate hypotheses, and relationship to the bone remodeling compartment." J Cell Biochem 103(2): 393-400.

Plastic adherent bone marrow stromal cells have become synonymous with skeletal stem cells, and perhaps rightfully so, as these cells have been extremely well characterized over the past four decades, since their original description by Friedenstein. However, although this cell population is useful as an experimental model of precursors for osteoblasts and other mesenchymal lineages, the precise role of bone marrow stromal cells in bone remodeling, fracture repair, or repair of non-skeletal tissues remains unclear. Moreover, there is a conceptual problem in terms of postulating that these cells are osteoblast precursors at sites of bone remodeling on trabecular surfaces adjacent to red marrow and yet having to posit potentially entirely different mechanisms for the origins of osteoblasts at sites of cortical bone remodeling distant from red marrow. Thus, the identification and characterization in recent years of non-adherent stem and osteoprogenitor cells in the bone marrow, of similar cells in the peripheral circulation, and of stem/osteoprogenitor cells arising either from the perivascular compartment (pericytes) or within the developing vascular wall itself, has suggested alternative candidate cell populations that may help to resolve the problem of postulating different mechanisms of remodeling in trabecular versus cortical bone. When coupled with our evolving understanding of the bone remodeling compartment (BRC), a closed cavity penetrated by capillaries which appears to be the site of remodeling in both trabecular and cortical bone, it is likely that our conceptual understanding of the fundamental mechanisms of bone remodeling will need to be modified.

Moioli, E. K., et al. (2008). "Synergistic actions of hematopoietic and mesenchymal stem/progenitor cells in vascularizing bioengineered tissues." PLoS One 3(12): e3922.

Poor angiogenesis is a major road block for tissue repair. The regeneration of virtually all tissues is limited by angiogenesis, given the diffusion of nutrients, oxygen, and waste products is limited to a few hundred micrometers. We postulated that co-transplantation of hematopoietic and mesenchymal stem/progenitor cells improves angiogenesis of tissue repair and hence the outcome of regeneration. In this study, we tested this hypothesis by using bone as a model whose regeneration is impaired unless it is vascularized. Hematopoietic stem/progenitor cells (HSCs) and mesenchymal stem/progenitor cells (MSCs) were isolated from each of three healthy human bone marrow samples and reconstituted in a porous scaffold. MSCs were seeded in micropores of 3D calcium phosphate (CP) scaffolds, followed by infusion of gel-suspended CD34(+) hematopoietic cells. Co-transplantation of CD34(+) HSCs and CD34(-) MSCs in microporous CP scaffolds subcutaneously in the dorsum of immunocompromised mice yielded vascularized tissue. The average vascular number of co-transplanted CD34(+) and MSC scaffolds was substantially greater than MSC transplantation alone. Human osteocalcin was expressed in the micropores of CP scaffolds and was significantly increased upon co-transplantation of MSCs and CD34(+) cells. Human nuclear staining revealed the engraftment of transplanted human cells in vascular endothelium upon co-transplantation of MSCs and CD34(+) cells. Based on additional in vitro results of endothelial differentiation of CD34(+) cells by vascular endothelial growth factor (VEGF), we adsorbed VEGF with co-transplanted CD34(+) and MSCs in the microporous CP scaffolds in vivo, and discovered that vascular number and diameter further increased, likely owing to the promotion of endothelial differentiation of CD34(+) cells by VEGF. Together, co-transplantation of hematopoietic and mesenchymal stem/progenitor cells may improve the regeneration of vascular dependent tissues such as bone, adipose, muscle and dermal grafts, and may have implications in the regeneration of internal organs.

Moll, G., et al. (2012). "Are therapeutic human mesenchymal stromal cells compatible with human blood?" Stem Cells 30(7): 1565-1574.

Multipotent mesenchymal stromal cells (MSCs) are tested in numerous clinical trials. Questions have been raised concerning fate and function of these therapeutic cells after systemic infusion. We therefore asked whether culture-expanded human MSCs elicit an innate immune attack, termed instant blood-mediated inflammatory reaction (IBMIR), which has previously been shown to compromise the survival and function of systemically infused islet cells and hepatocytes. We found that MSCs expressed hemostatic regulators similar to those produced by endothelial cells but displayed higher amounts of prothrombotic tissue/stromal factors on their surface, which triggered the IBMIR after blood exposure, as characterized by formation of blood activation markers. This process was dependent on the cell dose, the choice of MSC donor, and particularly the cell-passage number. Short-term expanded MSCs triggered only weak blood responses in vitro, whereas extended culture and coculture with activated lymphocytes increased their prothrombotic properties. After systemic infusion to patients, we found increased formation of blood activation markers, but no formation of hyperfibrinolysis marker D-dimer or acute-phase reactants with the currently applied dose of 1.0-3.0 x 10(6) cells per kilogram. Culture-expanded MSCs trigger the IBMIR in vitro and in vivo. Induction of IBMIR is dose-dependent and increases after prolonged ex vivo expansion. Currently applied doses of low-passage clinical-grade MSCs elicit only minor systemic effects, but higher cell doses and particularly higher passage cells should be handled with care. This deleterious reaction can compromise the survival, engraftment, and function of these therapeutic cells. Stem Cells2012;30:1565-1574.

Mummaneni, P. V., et al. (2004). "Contribution of recombinant human bone morphogenetic protein-2 to the rapid creation of interbody fusion when used in transforaminal lumbar interbody fusion: a preliminary report. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004." J Neurosurg Spine 1(1): 19-23.

OBJECT: The authors compared fusion rates in transforaminal lumbar interbody fusion (TLIFs) when using either autograft or bone morphogenetic protein (BMP) placed in the interbody space. METHODS: Between September 2002 and December 2003, the authors performed 44 TLIF operations. Follow-up data were available for 40 patients. Of the 40 procedures, 19 involved cages filled with iliac crest autograft (Group 1) and 21 involved cages filled with a medium kit of recombinant human (rh) BMP-2 (Group 2). In all Group 2 patients, one BMP sponge was placed anterior to the cage and another was placed within the cage. In 12 of the Group 2 patients, iliac crest autograft was placed posterior to the BMP-filled cage (Group 2A). In the remaining nine Group 2 patients, only local autograft was placed posterior to the BMP-filled cage (Group 2B). Assessment of fusion was performed using dynamic radiography at 3-month intervals. Outcomes were assessed using the Prolo Scale, and iliac crest donor site pain was measured using a Visual Analog Scale (VAS). The mean follow-up period was 9 months (range 3-18 months). In Group 1 patients, one pseudarthrosis was detected. In Group 2 patients, dynamic radiography demonstrated solid fusion in all patients except one in Group 2B. Fifty-eight percent of patients in whom iliac crest autograft was used complained of donor site pain 6 months after surgery (5 of 10 points on the VAS). Symptomatic foraminal bone formation was not observed in any Group 2 patient. CONCLUSIONS: The use of rhBMP-2 is safe in TLIFs when the sponges are placed away from the dura mater, and BMP promotes a more rapid fusion than iliac crest autograft alone. The use of rhBMP-2 in combination with local autograft is an excellent option for promoting solid fusion with TLIF, and it eliminates the possibility of iliac donor site pain.

Munoz, J. R., et al. (2005). "Human stem/progenitor cells from bone marrow promote neurogenesis of endogenous neural stem cells in the hippocampus of mice." Proc Natl Acad Sci U S A 102(50): 18171-18176.

Stem/progenitor cells from bone marrow and other sources have been shown to repair injured tissues by differentiating into tissue-specific phenotypes, by secreting chemokines, and, in part, by cell fusion. Here we prepared the stem/progenitor cells from human bone marrow (MSCs) and implanted athem into the dentate gyrus of the hippocampus of immunodeficient mice. The implanted human MSCs markedly increased the proliferation of endogenous neural stem cells that expressed the stem cell marker Sox2. Labeling of the mice with BrdUrd demonstrated that, 7 days after implantation of the human MSCs, BrdUrd-labeled endogenous cells migrated throughout the dorsal hippocampus (positive for doublecortin) and expressed markers for astrocytes and for neural or oligodendrocyte progenitors. Subpopulations of BrdUrd-labeled cells exhibited short cytoplasmic processes immunoreactive for nerve growth factor and VEGF. By 30 days after implantation, the newly generated cells expressed markers for more mature neurons and astrocytes. Also, subpopulations of BrdUrd-labeled cells exhibited elaborate processes immunoreactive for ciliary neurotrophic factor, neurotrophin-4/5, nerve growth factor, or VEGF. Therefore, implantation of human MSCs stimulated proliferation, migration, and differentiation of the endogenous neural stem cells that survived as differentiated neural cells. The results provide a paradigm to explain recent observations in which MSCs or related stem/progenitor cells were found to produce improvements in disease models even though a limited number of the cells engrafted.

Murawski, C. D., et al. (2011). "Bone marrow aspirate concentrate (BMAC) as a biological adjunct to the surgical treatment of osteochondral lesions of the talus." Techniques in Foot & Ankle Surgery 10(1): 18-27.

Murawski, C. D., et al. (2010). "A review of arthroscopic bone marrow stimulation techniques of the talus: The good, the bad, and the causes for concern." Cartilage 1(2): 137-144.

Murayama, T., et al. (2002). "Determination of bone marrow-derived endothelial progenitor cell significance in angiogenic growth factor-induced neovascularization in vivo." Exp Hematol 30(8): 967-972.

OBJECTIVE: Our laboratory and others recently provided evidence indicating that endothelial progenitor cells (EPCs) participate in postnatal neovascularization. However, the extent to which EPCs contribute to adult neovascularization remains unclear. To address this issue, we investigated the quantitative contribution of EPCs to newly formed vascular structures in an in vivo Matrigel plug assay and corneal micropocket assay. MATERIALS AND METHODS: Lethally irradiated FVB mice were transplanted with bone marrow (BM) mononuclear cells from transgenic mice constitutively expressing beta-galactosidase (beta-gal) encoded by the lacZ gene regulated by an endothelial-specific tie-2 promoter. Reconstitution of the transplanted BM leads to the expression of lacZ in mice, which is restricted to BM cells expressing tie-2. RESULTS: Four weeks after BM transplantation (BMT), tie-2/lacZ/BMT mice were implanted with either Matrigel containing fibroblast growth factor-2 subcutaneously or with a vascular endothelial growth factor pellet into the cornea. After 7 days, the Matrigel plug or the cornea was removed and analyzed by X-gal staining or immunostaining for beta-gal. X-gal staining of the Matrigel plug identified 5.7% +/- 1.2% of endothelial cells (ECs) as cells originated from BM-derived EPCs, whereas the more sensitive technique of immunofluorescence identified 26.5% +/- 0.9% of ECs. Similarly, EPC-derived cells comprised 5.0% +/- 2.4% and 17.7% +/- 3.6% of the ECs in corneal neovascularization identified by X-gal staining and immunohistochemistry, respectively. Ki67 staining of the corneal tissue documented that the majority of EPC-derived cells were actively proliferating in situ. CONCLUSION: These findings suggest that BM-derived EPCs make a significant contribution to angiogenic growth factor-induced neovascularization that may account for up to 26% of all ECs.

Murohara, T., et al. (1998). "Vascular endothelial growth factor/vascular permeability factor enhances vascular permeability via nitric oxide and prostacyclin." Circulation 97(1): 99-107.

BACKGROUND: Vascular endothelial growth factor (VEGF), an endothelial cell mitogen that promotes angiogenesis, was initially identified as a vascular permeability factor (VPF). Abundant evidence suggests that angiogenesis is preceded and/or accompanied by enhanced microvascular permeability. The mechanism by which VEGF/VPF increases vascular permeability (VP), however, has remained enigmatic. Accordingly, we used an in vivo assay of VP (Miles assay) to study the putative mediators of VEGF/VPF-induced permeability. METHODS AND RESULTS: VEGF/VPF and positive controls (platelet-activating factor [PAF], histamine, and bradykinin) all increased vascular permeability. Prior administration of the tyrosine kinase inhibitors genistein or herbimycin A prevented VEGF/VPF-induced permeability. Placenta growth factor, which binds to Flt-1/VEGF-R1 but not Flk-1/KDR/VEGF-R2 receptor tyrosine kinase, failed to increase permeability. Other growth factors such as basic fibroblast growth factor (FGF), acidic FGF, platelet-derived growth factor-BB, transforming growth factor-beta, scatter factor, and granulocyte macrophage-colony stimulating factor (8 to 128 ng) failed to increase permeability. VEGF/VPF-induced permeability was significantly attenuated by the nitric oxide (NO) synthase inhibitors N(omega)-nitro-L-arginine (10 mg/kg) or N(omega)-nitro-L-arginine methyl ester (20 mg/kg) and the cyclooxygenase inhibitor indomethacin (5 mg/kg). The inactive enantiomer N(omega)-nitro-D-arginine methyl ester (20 mg/kg) did not inhibit VEGF/VPF-induced permeability. In vitro studies confirmed that VEGF/VPF stimulates synthesis of NO and prostaglandin metabolites in microvascular endothelial cells. Finally, NO donors and the prostacyclin analogue taprostene administered together but not alone reproduced the increase in permeability observed with VEGF/VPF. CONCLUSIONS: These results implicate NO and prostacyclin produced by the interaction of VEGF/VPF with its Flk-1/KDR/VEGF-R2 receptor as mediators of VEGF/VPF-induced vascular permeability. Moreover, this property appears unique to VEGF/VPF among angiogenic cytokines.

Murry, C. E., et al. (2004). "Haematopoietic stem cells do not transdifferentiate into cardiac myocytes in myocardial infarcts." Nature 428(6983): 664-668.

The mammalian heart has a very limited regenerative capacity and, hence, heals by scar formation. Recent reports suggest that haematopoietic stem cells can transdifferentiate into unexpected phenotypes such as skeletal muscle, hepatocytes, epithelial cells, neurons, endothelial cells and cardiomyocytes, in response to tissue injury or placement in a new environment. Furthermore, transplanted human hearts contain myocytes derived from extra-cardiac progenitor cells, which may have originated from bone marrow. Although most studies suggest that transdifferentiation is extremely rare under physiological conditions, extensive regeneration of myocardial infarcts was reported recently after direct stem cell injection, prompting several clinical trials. Here, we used both cardiomyocyte-restricted and ubiquitously expressed reporter transgenes to track the fate of haematopoietic stem cells after 145 transplants into normal and injured adult mouse hearts. No transdifferentiation into cardiomyocytes was detectable when using these genetic techniques to follow cell fate, and stem-cell-engrafted hearts showed no overt increase in cardiomyocytes compared to sham-engrafted hearts. These results indicate that haematopoietic stem cells do not readily acquire a cardiac phenotype, and raise a cautionary note for clinical studies of infarct repair.

Muschler, G. F., et al. (1997). "Aspiration to obtain osteoblast progenitor cells from human bone marrow: the influence of aspiration volume." J Bone Joint Surg Am 79(11): 1699-1709.

Bone marrow contains osteoblast progenitor cells that can be obtained with aspiration and appear to arise from a population of pluripotential connective-tissue stem cells. When cultured in vitro under conditions that promote an osteoblastic phenotype, osteoblast progenitor cells proliferate to form colonies of cells that express alkaline phosphatase and, subsequently, a mature osteoblastic phenotype. We evaluated the number of nucleated cells in bone-marrow samples obtained with aspiration from the anterior iliac crest of thirty-two patients without systemic disease. There were nineteen male patients and thirteen female patients; the mean age was forty-one years (range, fourteen to seventy-seven years). The prevalence and concentration of the osteoblast progenitor cells also were determined, by placing the bone-marrow-derived cells into tissue-culture medium and counting the number of alkaline phosphatase-positive colony-forming units. In order to assess the effect of aspiration volume, two sequential experiments were performed. In the first experiment, aspiration volumes of one and two milliliters were compared. In the second experiment, aspiration volumes of two and four milliliters were compared. The mean prevalence of alkaline phosphatase-positive colony-forming units in the bone-marrow samples was thirty-six per one million nucleated cells (95 per cent confidence interval, 28 to 47); a mean of 2400 alkaline phosphatase-positive colony-forming units was obtained from a two-milliliter aspirate. There was a significant difference among the patients with respect to the number of alkaline phosphatase-positive colony-forming units in these bone-marrow samples (p < 0.001). Seventy per cent of this variation in the prevalence was due to variation among patients, and 20 per cent was due to variation among aspirates. The number of alkaline phosphatase-positive colony-forming units in the aspirate increased as the aspiration volume increased. However, contamination by peripheral blood also increased as the aspiration volume increased. An increase in the aspiration volume from one to four milliliters caused a decrease of approximately 50 per cent in the final concentration of alkaline phosphatase-positive colony-forming units in an average sample. CLINICAL RELEVANCE: On the basis of these data, we recommend that, when bone marrow is obtained with aspiration for use as a bone graft, the volume of aspiration from any one site should not be greater than two milliliters. A larger volume decreases the concentration of osteoblast progenitor cells because of dilution of the bone-marrow sample with peripheral blood. We estimate that four one-milliliter aspirates will provide almost twice the number of alkaline phosphatase-positive colony-forming units as will one four-milliliter aspirate. In addition, these data confirm that humans differ significantly from one another with respect to the cellularity of bone marrow and the prevalence of osteoblast progenitor cells. Additional studies are necessary to determine if the number or prevalence of alkaline phosphatase-positive colony-forming units in bone marrow is a determining factor in the efficacy of an autogenous bone or bone-marrow graft and to ascertain how the number and function of alkaline phosphatase-positive colony-forming units may change as a function of factors such as age, menopausal status, and selected diseases.

Muschler, G. F. and R. J. Midura (2002). "Connective tissue progenitors: practical concepts for clinical applications." Clin Orthop Relat Res(395): 66-80.

Tissue engineering can be defined as any effort to create or induce the formation of a specific tissue in a specific location through the selection and manipulation of cells, matrices, and biologic stimuli. The biologic concepts and the biochemical and biophysical principles on which these efforts are based have become an exciting and rapidly evolving field of biomedical research. More importantly, tissue engineering is becoming a clinical reality in the practice of orthopaedic surgery, providing patients and physicians with an expanding set of practical tools for effective therapy. New and improved matrices and bioactive factors inevitably will play important roles in the evolution of orthopaedic tissue engineering. However, tissue engineering never can stray far from fundamental biologic principles, and one of these is that cells do all the work. No new tissue forms except through the activity of living cells. No bone graft, no matrix, no growth factor, no cytokine can contribute to the generation or integration of new tissue, except through the influence it has on the behavior of cells. The efficacy of all current clinical tools depends entirely on the cells in the grafted site, particularly the small subset of stem cells and progenitor cells that are capable of generating new tissue. The current authors review a series of key biologic concepts related to the rational design and selection of composites of cells and matrices in contemporary bone grafting and tissue engineering efforts. The functional paradigms of stem cell biology are reviewed, including self renewal, asymmetric and symmetric mitosis, and lineage restriction. Several potential sources for autogenous stem cells for connective tissues are discussed. Finally, a simple mathematical model is introduced as a tool for understanding the functional demands placed on stem cells and progenitors in a graft site and to provide a conceptual framework for the rational design of cell matrix composite grafts.

Muschler, G. F., et al. (2004). "Engineering principles of clinical cell-based tissue engineering." J Bone Joint Surg Am 86-A(7): 1541-1558.

Tissue engineering is a rapidly evolving discipline that seeks to repair, replace, or regenerate specific tissues or organs by translating fundamental knowledge in physics, chemistry, and biology into practical and effective materials, devices, systems, and clinical strategies. Stem cells and progenitors that are capable of forming new tissue with one or more connective tissue phenotypes are available from many adult tissues and are defined as connective tissue progenitors. There are four major cell-based tissue-engineering strategies: (1) targeting local connective tissue progenitors where new tissue is desired, (2) transplanting autogenous connective tissue progenitors, (3) transplanting culture-expanded or modified connective tissue progenitors, and (4) transplanting fully formed tissue generated in vitro or in vivo. Stem cell function is controlled by changes in stem cell activation and self-renewal or by changes in the proliferation, migration, differentiation, or survival of the progeny of stem cell activation, the downstream progenitor cells. Three-dimensional porous scaffolds promote new tissue formation by providing a surface and void volume that promotes the attachment, migration, proliferation, and desired differentiation of connective tissue progenitors throughout the region where new tissue is needed. Critical variables in scaffold design and function include the bulk material or materials from which it is made, the three-dimensional architecture, the surface chemistry, the mechanical properties, the initial environment in the area of the scaffold, and the late scaffold environment, which is often determined by degradation characteristics. Local presentation or delivery of bioactive molecules can change the function of connective tissue progenitors (activation, proliferation, migration, differentiation, or survival) in a manner that results in new or enhanced local tissue formation. All cells require access to substrate molecules (oxygen, glucose, and amino acids). A balance between consumption and local delivery of these substrates is needed if cells are to survive. Transplanted cells are particularly vulnerable. Theoretical calculations can be used to explore the relationships among cell density, diffusion distance, and cell viability within a graft and to design improved strategies for transplantation of connective tissue progenitors. Rational strategies for tissue engineering seek to optimize new tissue formation through the logical selection of conditions that modulate the performance of connective tissue progenitors in a graft site to produce a desired tissue. This increasingly involves strategies that combine cells, matrices, inductive stimuli, and techniques that enhance the survival and performance of local or transplanted connective tissue progenitors.

Muschler, G. F., et al. (2004). "Engineering principles of clinical cell-based tissue engineering." J Bone Joint Surg Am 86-A(7): 1541-1558.

Muschler, G. F., et al. (2006). Comparison of bone marrow aspiration and bone core biopsy as methods for harvest and assay of human connective tissue progenitor. The Association of Bone and Joint Surgeons, Buenos Aires, Argentina.

Nakajima, H. (2011). "Role of transcription factors in differentiation and reprogramming of hematopoietic cells." Keio J Med 60(2): 47-55.

Differentiation of hematopoietic cells is a sequential process of cell fate decision originating from hematopoietic stem cells (HSCs), allowing multi- or oligopotent progenitors to commit to certain lineages. HSCs are cells that are able to self-renew and repopulate the marrow for the long term. They first differentiate into multipotent progenitors (MPPs), which give rise to common lymphoid progenitors (CLPs) and common myeloid progenitors (CMPs). CMPs then differentiate into granulocyte monocyte progenitors (GMPs) and megakaryocyte erythroid progenitors (MEPs), which are the precursors of granulocytes/monocytes and erythrocytes/megakaryocytes, respectively. Lineage specification at differentiation branch points is dictated by the activation of lineage-specific transcription factors such as C/EBPalpha, PU.1, and GATA-1. The role of these transcription factors is generally instructive, and the expression of a single factor can often determine cell fate. Differentiation was long regarded as an irreversible process, and it was believed that somatic cells would not change their fate once they were differentiated. This paradigm was first challenged by the finding that ectopic cytokine signals could change the fate of differentiation, probably through modulating internal transcription networks. Subsequently, we and others showed that virtually all progenitors, including CLPs, CMPs, GMPs, and MEPs, still retain differentiation plasticity, and they can be converted into lineages other than their own by ectopic activation of only a single lineage-specific transcription factor. These findings established a novel paradigm for cellular differentiation and opened up an avenue for artificially manipulating cell fate for clinical use.

Neiman, R. (2007). Treatment of tibial nonunion and delayed union by percutaneous injection of concentrated autologous stem cells: An alternative to open surgical repair - a case report. Roseville, CA, Orthopedic Trauma Surgeons of Northern California.

Nielsen, J. S. and K. M. McNagny (2008). "Novel functions of the CD34 family." J Cell Sci 121(Pt 22): 3683-3692.

For almost 30 years, the cell-surface protein CD34 has been widely used as a marker to assist in the identification and Summary isolation of hematopoietic stem cells (HSCs) and progenitors in preparation for bone-marrow transplantation. In addition, it has increasingly been used as a marker to help identify other tissue-specific stem cells, including muscle satellite cells and epidermal precursors. Despite its utility as a stem-cell marker, however, the function of CD34 has remained remarkably elusive. This is probably because: (1) it is subject to a range of tissue-specific post-transcriptional and post-translational modifications that are expected to alter its function dramatically; (2) the simple interpretation of CD34 gain- and loss-of-function experiments has been confounded by the overlapping expression of the two recently discovered CD34-related proteins podocalyxin and endoglycan; and (3) there has been a glaring lack of robust in vitro and in vivo functional assays that permit the structural and functional analysis of CD34 and its relatives. Here, we provide a brief review of the domain structure, genomic organization, and tissue distribution of the CD34 family. We also describe recent insights from gain- and loss-of-function experiments and improved assays, which are elucidating a fascinating role for these molecules in cell morphogenesis and migration.

Oest, M. E. (2007). Dual osteogenic and angiogenic growth factor delivery as a treatment for segmental bone defects. Biomedical Engineering. Georgia Institute of Technology, Georgia Institute of Technology. PhD: 250.

A new model of a critically-sized segmental femoral bone defect in rats was developed to enable in vivo imaging and facilitate post-mortem mechanical testing of samples. The critically-sized nature of the model was assessed and confirmed. The efficacy of sustained co-delivery of osteogenic (BMP-2 and TGF- Ò3) and angiogenic (VEGF) growth factors in promoting functional bone repair was assessed. Effects of scaffold modification in terms of geometry and composition were evaluated. The results indicated that co-delivery of BMP-2 and TGF- Ò3 resulted in a dose-dependent improvement in functional bone repair. Modification of the polylactide scaffold to include an absorbable ceramic component and a cored out geometry enhanced rate of union. Addition of VEGF to the scaffold treatment did not significantly impact revascularization of the defect site or functional repair of the bone defect. These data demonstrate that the complex environment of an acute bone defect requires different treatment strategies than simple ectopic models would suggest. A positive predictive correlation between bone repair parameters measured in vivo and mechanical functionality was established. The novel defect model demonstrated robustness and reproducibility. Implications for further research are discussed.

Ohtaki, H., et al. (2008). "Stem/progenitor cells from bone marrow decrease neuronal death in global ischemia by modulation of inflammatory/immune responses." Proc Natl Acad Sci U S A 105(38): 14638-14643.

Human mesenchymal stromal cells (hMSCs) were injected into the hippocampus of adult mice 1 day after transient global ischemia. The hMSCs both improved neurologic function and markedly decreased neuronal cell death of the hippocampus. Microarray assays indicated that ischemia up-regulated 586 mouse genes. The hMSCs persisted for <7 days, but they down-regulated >10% of the ischemia-induced genes, most of which were involved in inflammatory and immune responses. The hMSCs also up-regulated three mouse genes, including the neuroprotective gene Ym1 that is expressed by activated microglia/macrophages. In addition, the transcriptomes of the hMSC changed with up-regulation of 170 human genes and down-regulation of 54 human genes. Protein assays of the hippocampus demonstrated increased expression in microglia/macrophages of Ym1, the cell survival factor insulin-like growth factor 1, galectin-3, cytokines reflective of a type 2 T cell immune bias, and the major histocompatibility complex II. The observed beneficial effects of hMSCs were largely explained by their modulation of inflammatory and immune responses, apparently by alternative activation of microglia and/or macrophages.

Ohzono, K., et al. (1991). "Natural history of nontraumatic avascular necrosis of the femoral head." J Bone Joint Surg Br 73(1): 68-72.

We studied the natural history of nontraumatic avascular necrosis of the femoral head (ANFH) in 115 hips in 87 patients, 69 steroid-induced, 21 related to misuse of alcohol and 25 idiopathic. The average length of follow-up was over five years. Collapse occurred most often when the focus of bone necrosis occupied the weight-bearing surface of the femoral head. Flatness of the head due to subchondral fracture was an early manifestation of collapse. Classification into six types based upon the radiographic findings provided an accurate prognosis for individual cases of ANFH which is useful in planning treatment and in assessing its outcome.

Olmsted-Davis, E. A., et al. (2003). "Primitive adult hematopoietic stem cells can function as osteoblast precursors." Proc Natl Acad Sci U S A 100(26): 15877-15882.

Osteoblasts are continually recruited from stem cell pools to maintain bone. Although their immediate precursor is a plastic-adherent mesenchymal stem cell able to generate tissues other than bone, increasing evidence suggests the existence of a more primitive cell that can differentiate to both hematopoietic and mesenchymal cells. We show here that the "side population" (SP) of marrow stem cells, defined by their ability to rapidly expel a DNA-binding dye and to regenerate the hematopoietic compartment, can differentiate to osteoblasts through a mesenchymal intermediate. When transplanted into lethally irradiated mice, single gene-marked murine SP cells reconstituted depleted osteoprogenitor pools, such that a large proportion of the osteogenic cells in the epiphysis of long bone carried the donor SP cell marker. These findings suggest that the developmental capacity of SP cells is not restricted to the hematopoietic lineages but extends to osteogenic differentiation. This property not only elucidates a previously unrecognized step in osteoblast development, but also has intriguing implications for the use of SP cells in clinical orthopedics and stem cell-based disorders of bone.

Owen, M. (1980). "The origin of bone cells in the postnatal organism." Arthritis Rheum 23(10): 1073-1080.

Patel, A. N., et al. (2005). "Surgical treatment for congestive heart failure with autologous adult stem cell transplantation: a prospective randomized study." J Thorac Cardiovasc Surg 130(6): 1631-1638.

BACKGROUND: Autologous adult stem cell transplantation has been touted as the latest tool in regenerative medical therapy. Its potential for use in cardiovascular disease has only recently been recognized. A randomized study was conducted with a novel epicardial technique to deploy stem cells as an adjuvant to conventional revascularization therapy in patients with congestive heart failure. METHODS: After institutional review board and government approval, adult autologous stem cell transplantation (CD34+) was performed in patients with ischemic cardiomyopathy and an ejection fraction of less than 35% who were scheduled for primary off-pump coronary artery bypass grafting. Preoperatively, the patients underwent echocardiography, stress thallium imaging single photon emission computed tomography, and cardiac catheterization to identify ischemic regions of the heart and to guide in the selection of stem cell injection sites. The patients were prospectively randomized before the operative therapy was performed. Patient follow-up was 1, 3, and 6 months with echocardiography, single photon emission computed tomography, and angiography. RESULTS: There were 20 patients enrolled in the study. Ten patients had successful subepicardial transplantation of autologous stem cells into ischemic myocardium. The other 10 patients, the control group, only had off-pump coronary artery bypass grafting. There were 8 male and 2 female subjects in each group. The median number of grafts performed was 1 in both groups. On angiographic follow-up, all grafts were patent at 6 months. The ejection fractions of the off-pump coronary artery bypass grafting group versus the off-pump coronary artery bypass grafting plus stem cell transplantation group were as follows: preoperative, 30.7% +/- 2.5% versus 29.4% +/- 3.6%; 1 month, 36.4% +/- 2.6% versus 42.1% +/- 3.5%; 3 months, 36.5% +/- 3.0% versus 45.5% +/- 2.2%; and 6 months, 37.2% +/- 3.4% versus 46.1% +/- 1.9% (P < .001). There were no perioperative arrhythmias or neurologic or ischemic myocardial events in either group. CONCLUSIONS: Autologous stem cell transplantation led to significant improvement in cardiac function in patients undergoing off-pump coronary artery bypass grafting for ischemic cardiomyopathy. Further investigation is required to quantify the optimal timing and specific cellular effects of the therapy.

Perin, E. C., et al. (2003). "Transendocardial, autologous bone marrow cell transplantation for severe, chronic ischemic heart failure." Circulation 107(18): 2294-2302.

BACKGROUND: This study evaluated the hypothesis that transendocardial injections of autologous mononuclear bone marrow cells in patients with end-stage ischemic heart disease could safely promote neovascularization and improve perfusion and myocardial contractility. METHODS AND RESULTS: Twenty-one patients were enrolled in this prospective, nonrandomized, open-label study (first 14 patients, treatment; last 7 patients, control). Baseline evaluations included complete clinical and laboratory evaluations, exercise stress (ramp treadmill), 2D Doppler echocardiogram, single-photon emission computed tomography perfusion scan, and 24-hour Holter monitoring. Bone marrow mononuclear cells were harvested, isolated, washed, and resuspended in saline for injection by NOGA catheter (15 injections of 0.2 cc). Electromechanical mapping was used to identify viable myocardium (unipolar voltage > or =6.9 mV) for treatment. Treated and control patients underwent 2-month noninvasive follow-up, and treated patients alone underwent a 4-month invasive follow-up according to standard protocols and with the same procedures used as at baseline. Patient population demographics and exercise test variables did not differ significantly between the treatment and control groups; only serum creatinine and brain natriuretic peptide levels varied in laboratory evaluations at follow-up, being relatively higher in control patients. At 2 months, there was a significant reduction in total reversible defect and improvement in global left ventricular function within the treatment group and between the treatment and control groups (P=0.02) on quantitative single-photon emission computed tomography analysis. At 4 months, there was improvement in ejection fraction from a baseline of 20% to 29% (P=0.003) and a reduction in end-systolic volume (P=0.03) in the treated patients. Electromechanical mapping revealed significant mechanical improvement of the injected segments (P<0.0005) at 4 months after treatment. CONCLUSIONS: Thus, the present study demonstrates the relative safety of intramyocardial injections of bone marrow-derived stem cells in humans with severe heart failure and the potential for improving myocardial blood flow with associated enhancement of regional and global left ventricular function.

Peroni, D., et al. (2008). "Stem molecular signature of adipose-derived stromal cells." Exp Cell Res 314(3): 603-615.

It has recently been shown that adipose tissue is an abundant and easily accessible source of stromal progenitor cells (ADSCs, adipose-derived stromal cells), resembling the mesenchymal stem cells (MSCs) obtained from adult bone marrow. However, the identification of these two lineages is still controversial and even the stem cell nature of ADSCs is doubted. In this study, we examined the "stemness" transcriptional profile of ADSCs and BM-MSCs, with two aims: (1) to compare their "stem cell molecular signature" and (2) to dissect their constitutive expression pattern for molecules involved in tissue development, homeostasis and repair. As well as several molecules involved in matrix remodeling and adult tissue angiogenesis and repair, we detected the expression of genes UTF-1, Nodal, and Snail2, which are known to be expressed by embryonic stem cells but have been never described in other stem lineages. In addition, for the first time we described the transcriptional profile of human BM-MSCs and ADSCs for the CD44 splice variants, which are determinant in cell trafficking during embryonic development, in adult tissue homeostasis and also in tumor dissemination. Thus, our findings strongly support a close relationship between ADSCs and BM-MSCs, suggest an unexpected similarity between MSCs and embryonic stem cells, and possibly support the potential therapeutic application of ADSCs.

Phemister, D. B. (1930). "Repair of bone in the presence of aseptic necrosis resulting from fractures, transplantations, and vascular obstruction." J Bone Joint Surg 12(4): 769-787.

Piao, C. S., et al. (2009). "The role of stem cell factor and granulocyte-colony stimulating factor in brain repair during chronic stroke." J Cereb Blood Flow Metab 29(4): 759-770.

Chronic stroke is a highly important but under-investigated scientific problem in neurologic research. We have reported earlier that stem cell factor (SCF) in combination with granulocyte-colony stimulating factor (G-CSF) treatment during chronic stroke improves functional outcomes. Here we have determined the contribution of bone marrow-derived cells in angiogenesis and neurogenesis, which are enhanced by SCF+G-CSF treatment during chronic stroke. Using bone marrow tracking, flow cytometry, 2-photon live brain imaging, and immunohistochemistry, we observed that the levels of circulating bone marrow stem cells (BMSCs) (CD34+/c-kit+) were significantly increased by SCF+G-CSF treatment. In addition, live brain imaging revealed that numerous bone marrow-derived cells migrate into the brain parenchyma in the treated mice. We also found that bone marrow-derived cells, bone marrow-derived endothelial cells, vascular density, and bone marrow-derived neurons were significantly augmented by SCF+G-CSF. It is interesting that, in addition to the increase in bone marrow-derived endothelial cells, the number of bone marrow-derived pericytes was reduced after SCF+G-CSF treatment during chronic stroke. These data suggest that SCF+G-CSF treatment can enhance repair of brain damage during chronic stroke by mobilizing BMSCs, and promoting the contribution of bone marrow-derived cells to angiogenesis and neurogenesis.

Pitchford, S. C., et al. (2009). "Differential Mobilization of Subsets of Progenitor Cells from the Bone Marrow." Cell Stem Cell 4(1): 62-72.

Platzbecker, U., et al. (2001). "Spleen enlargement in healthy donors during G-CSF mobilization of PBPCs." Transfusion 41(2): 184-189.

BACKGROUND: Recombinant human G-CSF is widely used to mobilize PBPCs in healthy donors for allogeneic transplantation. There have been concerns about donor safety because of splenic ruptures during G-CSF application. To address this problem, changes in splenic size in 91 healthy donors during G-CSF mobilization of allogeneic PBPCs were investigated. STUDY DESIGN AND METHODS: For mobilization, G-CSF in a dosage of 7.5 microg per kg per day was administered for 5 days and PBPC collection started Day 5. Splenic size was determined by ultrasound before G-CSF application was started and on the day of the first apheresis. RESULTS: The mean increase in splenic length was 11 mm (range, 0-28 mm; p<0.0001), whereas a mean increase of 5 mm in width (range, 0-14 mm; p<0.0001) was measured. No major side effects could be observed. There was no significant correlation between the increase in splenic size and the hematologic values, or the age and body-mass index. In a multivariant analysis, no independent risk factor for the development of a spleen enlargement over 19 mm in length and 9 mm in thickness was found in 20 percent of investigated donors. CONCLUSION: In this prospective trial, a significant spleen enlargement was observed in healthy donors during G-CSF mobilization of allogeneic PBPCs. Further investigations are needed to define the degree of spleen enlargement with higher G-CSF dosages to improve donor safety.

Pomerantz, J. and H. M. Blau (2004). "Nuclear reprogramming: a key to stem cell function in regenerative medicine." Nat Cell Biol 6(9): 810-816.

The goal of regenerative medicine is to restore form and function to damaged tissues. One potential therapeutic approach involves the use of autologous cells derived from the bone marrow (bone marrow-derived cells, BMDCs). Advances in nuclear transplantation, experimental heterokaryon formation and the observed plasticity of gene expression and phenotype reported in multiple phyla provide evidence for nuclear plasticity. Recent observations have extended these findings to show that endogenous cells within the bone marrow have the capacity to incorporate into defective tissues and be reprogrammed. Irrespective of the mechanism, the potential for new gene expression patterns by BMDCs in recipient tissues holds promise for developing cellular therapies for both proliferative and post-mitotic tissues.

Purton, L. E. and D. T. Scadden (2008). The hematopoietic stem cell niche. StemBook. Cambridge (MA).

The hematopoietic stem cell (HSC) niche is the anatomical location in which HSCs reside and self-renew. The HSCs outside the niche do not self-renew and commence the process of differentiation to ultimately produce mature blood cells. In recent years there have been a large number of studies performed to identify the cell types that comprise the hematopoietic stem cell niche, and to determine what factors are important contributions to HSC niche function. These studies are important not only for our understanding of how hematopoietic stem cells are regulated in vivo, but are also likely to be critical for designing stem cell targeted therapies. Here we summarize the history, recent studies, concepts and controversies in these analyses of the hematopoietic stem cell niche, and their implications for the future.

Qiu, J., et al. (2004). "Regenerative response in ischemic brain restricted by p21cip1/waf1." J Exp Med 199(7): 937-945.

Neural precursor cells from adults have exceptional proliferative and differentiative capability in vitro yet respond minimally to in vivo brain injury due to constraining mechanisms that are poorly defined. We assessed whether cell cycle inhibitors that restrict stem cell populations in other tissues may participate in limiting neural stem cell reactivity in vivo. The cyclin-dependent kinase inhibitor, p21cip1/waf1 (p21), maintains hematopoietic stem cell quiescence, and we evaluated its role in the regenerative response of neural tissue after ischemic injury using the mice deficient in p21. Although steady-state conditions revealed no increase in primitive cell proliferation in p21-null mice, a significantly larger fraction of quiescent neural precursors was activated in the hippocampus and subventricular zone after brain ischemia. The hippocampal precursors migrated and differentiated into a higher number of neurons after injury. Therefore, p21 is an intrinsic suppressor to neural regeneration after brain injury and may serve as a common molecular regulator restricting proliferation among stem cell pools from distinct tissue types.

Quesenberry, P. J., et al. (2004). "Stem cell plasticity: an overview." Blood Cells Mol Dis 32(1): 1-4.

The capacity of adult bone marrow cells to convert to cells of other tissues, referred to by many as stem cell plasticity, was the focus of the meeting in Providence entitled "Challenges in the Era of Stem Cell Plasticity". The meeting provided a showcase for the many impressive positive results on tissue restoration including the capacity of purified marrow stem cells to restore heart, skin, and liver function in impaired mice or humans. This area of research has become a center of controversy, although it is not clear why. Calls for clonality, robustness, and function have been shown to be erroneous or premature. A call for clonality (which has been shown nicely in one study) is meaningless on a predefined stem cell population which is intrinsically heterogeneous, as they all are. Robustness means nothing; it all depends on the details of the situation. Function on an organ level is, of course, the goal of many investigators and should not be raised as a limiting consideration. Lastly, fusion has been highlighted as undermining studies with adult stem cells. It, of course, does not. Fusion is simply a means to a final goal, which occurs in certain settings of marrow conversions (transdifferentiation) and not in others. We hypothesize that the conversion phenomena may, in fact, be due to one or several marrow stem cells with broad differentiation potential which can be expressed when the cell is placed in an environment with the appropriate inductive signals. Furthermore, initial events may be relatively rare and significant conversion numbers may be obtained with massive or ongoing selection. Fusion appears in an initial mechanism in some cases and not in others. Overall, the therapeutic potential of adult marrow stem cells is very intriguing, and successful use therapeutically will probably depend on definition of the most appropriate transplant model and tissue injury.

Quesenberry, P. J. and J. M. Aliotta (2010). "Cellular phenotype switching and microvesicles." Adv Drug Deliv Rev 62(12): 1141-1148.

Cell phenotype alteration by cell-derived vesicles presents a new aspect for consideration of cell fate. Accumulating data indicates that vesicles from many cells interact with or enter different target cells from other tissues, altering their phenotype toward that of the cell releasing the vesicles. Cells may be changed by direct interactions, transfer of cell surface receptors or epigenetic reprogramming via transcriptional regulators. Induced epigenetic changes appear to be stable and result in significant functional effects. These data force a reconsideration of the cellular context in which transcription regulates the proliferative and differentiative fate of tissues and suggests a highly plastic cellular system, which might underlay a relatively stable tissue system. The capacity of marrow to convert to non-hematopoietic cells related to vesicle cross-communication may underlie the phenomena of stem cell plasticity. Additionally, vesicles have promise in the clinical arenas of disease biomarkers, tissue restoration and control of neoplastic cell growth.

Quesenberry, P. J., et al. (2010). "Stem cell plasticity revisited: the continuum marrow model and phenotypic changes mediated by microvesicles." Exp Hematol 38(7): 581-592.

The phenotype of marrow hematopoietic stem cells is determined by cell-cycle state and microvesicle entry into the stem cells. The stem cell population is continually changing based on cell-cycle transit and can only be defined on a population basis. Purification of marrow stem cells only addresses the heterogeneity of these populations. When whole marrow is studied, the long-term repopulating stem cells are in active cell cycle. However, with some variability, when highly purified stem cells are studied, the cells appear to be dormant. Thus, the study of purified stem cells is intrinsically misleading. Tissue-derived microvesicles enhanced by injury effect the phenotype of different cell classes. We propose that previously described stem cell plasticity is due to microvesicle modulation. We further propose a stem cell population model in which the individual cell phenotypes continually change, but the population phenotype is relatively stable. This, in turn, is modulated by microvesicle and microenvironmental influences.

Rabbany, S. Y., et al. (2003). "Molecular pathways regulating mobilization of marrow-derived stem cells for tissue revascularization." Trends Mol Med 9(3): 109-117.

Adult bone marrow is a rich reservoir of hematopoietic and vascular stem and progenitor cells. Mobilization and recruitment of these cells are essential for tissue revascularization. Physiological stress, secondary to tissue injury or tumor growth, results in the release of angiogenic factors, including vascular endothelial growth factor (VEGF), which promotes mobilization of stem cells to the circulation, contributing to the formation of functional vasculature. VEGF interacts with its receptors, VEGFR2 and VEGFR1, expressed on endothelial and hematopoietic stem cells, and thereby promotes recruitment of these cells to neo-angiogenic sites, accelerating the revascularization process. The mobilization of stem cells from marrow is a dynamic process, regulated by shear stress imparted by blood flow, and the activation of metalloproteinases that induce the release of 'Kit ligand', facilitating egress from the marrow to the circulation. Identification of the molecular pathways that support the proliferation and differentiation of vascular stem and progenitor cells will open up new avenues for the design of clinical trials to accelerate tissue vascularization and organogenesis.

Ramos-Mejia, V., et al. (2012). "Residual Expression of the Reprogramming Factors Prevents Differentiation of iPSC Generated from Human Fibroblasts and Cord Blood CD34+ Progenitors." PLoS One 7(4): e35824.

Human induced pluripotent stem cells (hiPSC) have been generated from different tissues, with the age of the donor, tissue source and specific cell type influencing the reprogramming process. Reprogramming hematopoietic progenitors to hiPSC may provide a very useful cellular system for modelling blood diseases. We report the generation and complete characterization of hiPSCs from human neonatal fibroblasts and cord blood (CB)-derived CD34+ hematopoietic progenitors using a single polycistronic lentiviral vector containing an excisable cassette encoding the four reprogramming factors Oct4, Klf4, Sox2 and c-myc (OKSM). The ectopic expression of OKSM was fully silenced upon reprogramming in some hiPSC clones and was not reactivated upon differentiation, whereas other hiPSC clones failed to silence the transgene expression, independently of the cell type/tissue origin. When hiPSC were induced to differentiate towards hematopoietic and neural lineages those hiPSC which had silenced OKSM ectopic expression displayed good hematopoietic and early neuroectoderm differentiation potential. In contrast, those hiPSC which failed to switch off OKSM expression were unable to differentiate towards either lineage, suggesting that the residual expression of the reprogramming factors functions as a developmental brake impairing hiPSC differentiation. Successful adenovirus-based Cre-mediated excision of the provirus OKSM cassette in CB-derived CD34+ hiPSC with residual transgene expression resulted in transgene-free hiPSC clones with significantly improved differentiation capacity. Overall, our findings confirm that residual expression of reprogramming factors impairs hiPSC differentiation.

Rampon, C., et al. (2008). "Molecular mechanism of systemic delivery of neural precursor cells to the brain: assembly of brain endothelial apical cups and control of transmigration by CD44." Stem Cells 26(7): 1673-1682.

Systemically injected neural precursor cells (NPCs) were unexpectedly shown to reach the cerebral parenchyma and induce recovery in various diffuse brain pathologies, including animal models of multiple sclerosis. However, the molecular mechanisms supporting NPC migration across brain endothelium remain elusive. Brain endothelium constitutes the blood-brain barrier, which uniquely controls the access of drugs and trafficking of cells, including leukocytes, from the blood to the brain. Taking advantage of the availability of in vitro models of human and rat blood-brain barrier developed in our laboratory and validated by us and others, we show here that soluble hyaluronic acid, the major ligand of the adhesion molecule CD44, as well as anti-CD44 blocking antibodies, largely prevents NPC adhesion to and migration across brain endothelium in inflammatory conditions. We present further evidence that NPCs, surprisingly, induce the formation of apical cups at the surface of brain endothelial cells, enriched in CD44 and other adhesion molecules, thus hijacking the endothelial signaling recently shown to be involved in leukocyte extravasation. These results demonstrate the pivotal role of CD44 in the trans-endothelial migration of NPCs across brain endothelial cells: we propose that they may help design new strategies for the delivery of therapeutic NPCs to the brain by systemic administration.

Ratajczak, M. Z., et al. (2011). "Identification of very small embryonic/epiblast-like stem cells (VSELs) circulating in peripheral blood during organ/tissue injuries." Methods Cell Biol 103: 31-54.

We have identified in adult tissues a population of pluripotent very small embryonic/epiblast-like stem cells (VSELs) that we hypothesize are deposited at onset of gastrulation in developing tissues and play an important role as backup population of tissue-specific/committed stem cells. We envision that during steady-state conditions these cells may be involved in tissue rejuvenation and in processes of regeneration/repair after organ injuries. VSELs similarly as epiblast-derived migrating primordial germ cells change the epigenetic signature of some of the imprinted genes and therefore remain quiescent in adult tissues. These epigenetic changes in methylation status of imprinted genes prevent them also from teratoma formation. Mounting evidence indicates that VSELs are mobilized into peripheral blood during tissue/organ injuries and enumeration of these cells may be of prognostic value (e.g., in stroke or heart infarct). In this chapter, we will present FACS-based strategies to detect and enumerate these cells in human peripheral blood and umbilical cord blood.

Rigotti, G., et al. (2007). "Clinical treatment of radiotherapy tissue damage by lipoaspirate transplant: a healing process mediated by adipose-derived adult stem cells." Plast Reconstr Surg 119(5): 1409-1422; discussion 1423-1404.

BACKGROUND: There is evidence that stem cells contribute to the restoration of tissue vascularization and organ function. The objective of this study was to assess the presence of adipose-derived adult stem cells left in their natural scaffold in the purified lipoaspirate and to assess the clinical effectiveness of lipoaspirate transplantation in the treatment of radiation side effects. METHODS: This study was designed beginning with surgical procedures in 2002 and envisaging a continuous patient follow-up to 31 months. Twenty consecutive patients undergoing therapy for side effects of radiation treatment with severe symptoms or irreversible function damage (LENT-SOMA scale grade 3 and 4) were enrolled. Purified autologous lipoaspirates (60 to 120 cc) taken from a healthy donor site were administered by repeated low-invasive computer-assisted injection. Therapy outcomes were assessed by symptoms classification according to the LENT-SOMA scale, cytofluorimetric characterization, and ultrastructural evaluation of targeted tissue. RESULTS: In the isolated stromal vascular fraction of 2 cc of human lipoaspirate, cells with mesenchymal stem cell physical properties and immunophenotype were in average 1.07 +/- 0.5 percent (n = 4), with a clonogenic fraction of 0.139 percent. At least 1.02 x 10(3) colony-forming units-fibroblast were present in each lipoaspirate. Ultrastructure of target tissue systematically exhibited progressive regeneration, including neovessel formation and improved hydration. Clinical outcomes led to a systematic improvement or remission of symptoms in all evaluated patients, including otherwise untreatable patients exhibiting initial irreversible functional damage. CONCLUSIONS: This surgical procedure is a low-invasive therapeutic approach for resolving the late side effects of radiotherapy. According to the proposed hypothesis of the ischemic nature of radiolesions, treatment with lipoaspirate transplantation is potentially extended to other forms of microangiopathies.

Rivron, N. C., et al. (2012). "Tissue deformation spatially modulates VEGF signaling and angiogenesis." Proc Natl Acad Sci U S A.

Physical forces play a major role in the organization of developing tissues. During vascular development, physical forces originating from a fluid phase or from cells pulling on their environment can alter cellular signaling and the behavior of cells. Here, we observe how tissue deformation spatially modulates angiogenic signals and angiogenesis. Using soft lithographic templates, we assemble three-dimensional, geometric tissues. The tissues contract autonomously, change shape stereotypically and form patterns of vascular structures in regions of high deformations. We show that this emergence correlates with the formation of a long-range gradient of Vascular Endothelial Growth Factor (VEGF) in interstitial cells, the local overexpression of the corresponding receptor VEGF receptor 2 (VEGFR-2) and local differences in endothelial cells proliferation. We suggest that tissue contractility and deformation can induce the formation of gradients of angiogenic microenvironments which could contribute to the long-range patterning of the vascular system.

Roh, J. S., et al. (2013). "Allogeneic morphogenetic protein vs. recombinant human bone morphogenetic protein-2 in lumbar interbody fusion procedures: a radiographic and economic analysis." J Orthop Surg Res 8(1): 49.

BACKGROUND: Since the introduction of rhBMP-2 (Infuse(R)) in 2002, surgeons have had an alternative substitute to autograft and its related donor site morbidity. Recently, the prevalence of reported adverse events and complications related to the use of rhBMP-2 has raised many ethical and legal concerns for surgeons. Additionally, the cost and decreasing reimbursement landscape of rhBMP-2 use have required identification of a viable alternative. Osteo allogeneic morphogenetic protein (OsteoAMP(R)) is a commercially available allograft-derived growth factor rich in osteoinductive, angiogenic, and mitogenic proteins. This study compares the radiographic fusion outcomes between rhBMP-2 and OsteoAMP allogeneic morphogenetic protein in lumbar interbody fusion spine procedures. METHODS: Three hundred twenty-one (321) patients from three centers underwent a transforaminal lumbar interbody fusion (TLIF) or lateral lumbar interbody fusion (LLIF) procedure and were assessed by an independent radiologist for fusion and radiographically evident complications. The independent radiologist was blinded to the intervention, product, and surgeon information. Two hundred and twenty-six (226) patients received OsteoAMP with autologous local bone, while ninety-five (95) patients received Infuse with autologous local bone. Patients underwent radiographs (x-ray and/or CT) at standard postoperative follow-up intervals of approximately 1, 3, 6, 12, and 18 months. Fusion was defined as radiographic evidence of bridging across endplates, or bridging from endplates to interspace disc plugs. Osteobiologic surgical supply costs were also analyzed to ascertain cost differences between OsteoAMP and rhBMP-2. RESULTS: OsteoAMP produced higher rates of fusion at 6, 12, and 18 months (p <= 0.01). The time required for OsteoAMP to achieve fusion was approximately 40 % less than rhBMP-2 with approximately 70 % fewer complications. Osteobiologic supply costs were 80.5 % lower for OsteoAMP patients (73.7 % lower per level) than for rhBMP-2. CONCLUSIONS: Results of this study indicate that OsteoAMP is a viable alternative to rhBMP-2 both clinically and economically when used in TLIF and LLIF spine procedures.

Romih, M., et al. (2005). "The vertebral interbody grafting site's low concentration in osteogenic progenitors can greatly benefit from addition of iliac crest bone marrow." Eur Spine J 14(7): 645-648.

The ability of bone substitutes to promote bone fusion is contingent upon the presence of osteoinductive factors in the bone environment at the fusion site. Osteoblast progenitor cells are among these environmental osteoinductive factors, and one of the most abundant and available sources of osteoblastic cells is the bone marrow. As far as biological conditions are concerned, the vertebral interbody space appears as a favorable site for fusion, as it is surrounded by spongy bone, theoretically rich in osteogenic cells. This site may, however, not be as rich in osteogenic precursor cells especially at the time of grafting, because decortication of the vertebral end plates during the grafting process may modify cell content of the surrounding spongy bone. We tested this hypothesis by comparing the abundance of human osteogenic precursor cells in bone marrow derived from the iliac crest, the vertebral body, and the decorticated intervertebral body space. The number of potential osteoblast progenitors in each site was estimated by counting the alkaline phosphatase-expressing colony-forming units (CFU-AP). The results, however, demonstrate that the vertebral interbody space is actually poorer in osteoprogenitor cells than the iliac crest (P<0.001) and vertebral body (P<0.01), especially at the time of graft implantation. In light of our results, we advocate addition of iliac crest bone marrow aspirate to increase the success rate of vertebral interbody fusion.

Rubin, R. and D. S. Strayer (2008). Rubin's pathology : clinicopathologic foundations of medicine. Philadelphia, Wolters Kluwer/Lippincott Williams & Wilkins.

Ryan, D. H. (2010). Examination of the marrow. Williams Hematology. P. J. T., K. K., L. M.A., K. T.J. and S. U. New York, McGraw-Hill.

Saigawa, T., et al. (2004). "Clinical application of bone marrow implantation in patients with arteriosclerosis obliterans, and the association between efficacy and the number of implanted bone marrow cells." Circ J 68(12): 1189-1193.

BACKGROUND: There have been a number of recent reports on the use of autologous bone marrow implantation (BMI) in the treatment of peripheral arterial disease, with a clinical response rate of approximately 70%. However, the factors that influence efficacy have not yet been clarified. We have analyzed the relationship between the number of implanted bone marrow cells and the clinical efficacy of BMI. METHODS AND RESULTS: Eight patients with arteriosclerosis obliterans were treated with BMI. Bone marrow was aspirated from the ilium (500-1,000 ml), the mononuclear cells were separated and then were implanted. The clinical effectiveness of BMI was evaluated by assessing changes in the ankle-brachial pressure index (ABI) and the transcutaneous oxygen pressure (TcO2) between the pre-treatment baseline, with follow-up testing at 4 weeks. These changes were defined as DeltaABI and DeltaTcO2. The mean number of CD34-positive cells was 1.04+/-0.60 x10(6) /kg body weight. There was a strong correlation between the number of CD34-positive cells and DeltaABI (r=0.754, p=0.028). CONCLUSIONS: It is likely that the number of implanted CD34-positive cells is one of the primary factors that influence the clinical efficacy of BMI.

Sandhu, H. S., et al. (2001). "Demineralized bone matrix, bone morphogenetic proteins, and animal models of spine fusion: an overview." Eur Spine J 10 Suppl 2: S122-131.

Preclinical investigations on the use of bone morphogenetic proteins (BMP) in the spine have yielded promising results. This has led to the preliminary introduction of these growth factors in controlled clinical trials. Initial data made available suggest that these differentiating factors will play a major role in the treatment of spinal disorders in the future. This article reviews key preclinical studies and their results that formed the basis for introduction into clinical trials. Non-primate and non-human primate models of spine fusion with BMP are reviewed objectively, and important issues regarding carrier, dose, and site of implantation are discussed. Finally, exciting new gene therapy research is discussed, with comments made on its applicability for the future.

Schaffler, A. and C. Buchler (2007). "Concise review: adipose tissue-derived stromal cells--basic and clinical implications for novel cell-based therapies." Stem Cells 25(4): 818-827.

Compared with bone marrow-derived mesenchymal stem cells, adipose tissue-derived stromal cells (ADSC) do have an equal potential to differentiate into cells and tissues of mesodermal origin, such as adipocytes, cartilage, bone, and skeletal muscle. However, the easy and repeatable access to subcutaneous adipose tissue and the simple isolation procedures provide a clear advantage. Since extensive reviews focusing exclusively on ADSC are rare, it is the aim of this review to describe the preparation and isolation procedures for ADSC, to summarize the molecular characterization of ADSC, to describe the differentiation capacity of ADSC, and to discuss the mechanisms and future role of ADSC in cell therapy and tissue engineering. An initial effort has also been made to differentiate ADSC into hepatocytes, endocrine pancreatic cells, neurons, cardiomyocytes, hepatocytes, and endothelial/vascular cells. Whereas the lineage-specific differentiation into cells of mesodermal origin is well understood on a molecular basis, the molecular key events and transcription factors that initially allocate the ADSC to a lineage-specific differentiation are almost completely unknown. Decoding these molecular mechanisms is a prerequisite for developing novel cell therapies.

Schechner, J. S., et al. (2000). "In vivo formation of complex microvessels lined by human endothelial cells in an immunodeficient mouse." Proc Natl Acad Sci U S A 97(16): 9191-9196.

We have identified conditions for forming cultured human umbilical vein endothelial cells (HUVEC) into tubes within a three-dimensional gel that on implantation into immunoincompetent mice undergo remodeling into complex microvessels lined by human endothelium. HUVEC suspended in mixed collagen/fibronectin gels organize into cords with early lumena by 24 h and then apoptose. Twenty-hour constructs, s.c. implanted in immunodeficient mice, display HUVEC-lined thin-walled microvessels within the gel 31 days after implantation. Retroviral-mediated overexpression of a caspase-resistant Bcl-2 protein delays HUVEC apoptosis in vitro for over 7 days. Bcl-2-transduced HUVEC produce an increased density of HUVEC-lined perfused microvessels in vivo compared with untransduced or control-transduced HUVEC. Remarkably, Bcl-2- but not control-transduced HUVEC recruit an ingrowth of perivascular smooth-muscle alpha-actin-expressing mouse cells at 31 days, which organize by 60 days into HUVEC-lined multilayered structures resembling true microvessels. This system provides an in vivo model for dissecting mechanisms of microvascular remodeling by using genetically modified endothelium. Incorporation of such human endothelial-lined microvessels into engineered synthetic skin may improve graft viability, especially in recipients with impaired angiogenesis.

Scholfield, R. (1978). "The relationship between the spleen colony-forming cell and the haemopoietic stem cell." Blood Cells 4: 7-25.

Several experimental findings that are inconsistent with the view that the spleen colony-forming cell (CFU-S) is the primary haemopoietic stem cell are reviewed. Recovery of CFU-S, both quantitatively and qualitatively, can proceed differently depending upon the cytotoxic agent or regime used to bring about the depletion. The virtual immortality of the stem cell population is at variance with evidence that the CFU-S population has an 'age-structure' which has been invoked by several workers to explain experimental and clinical observations. To account for these inconsistencies, a hypothesis is proposed in which the stem cell is seen in association with other cells which determine its behaviour. It becomes essentially a fixed tissue cell. Its maturation is prevented and, as a result, its continued proliferation as a stem cell is assured. Its progeny, unless they can occupy a similar stem cell 'niche', are first generation colony-forming cells, which proliferate and mature to acquire a high probability of differentiation, i.e., they have an age-structure. Some of the experimental situations reviewed are discussed in relation to the proposed hypothesis.

Schrezenmeier, H. and E. Seifried (2010). "Buffy-coat-derived pooled platelet concentrates and apheresis platelet concentrates: which product type should be preferred?" Vox Sang 99(1): 1-15.

There is an ongoing debate whether platelet concentrates (PCs) prepared from either whole-blood donations or by plateletpheresis are superior. Usage of these two product types varies greatly between countries and individual institutions. Some use mainly apheresis PCs; others prefer pooled PCs which are produced from whole-blood donations. This review summarizes the existing information on these product types. In the first part data on quality, efficacy and safety are reviewed. It is important to note that the issue cannot be answered just by comparing 'the' apheresis platelet concentrate versus 'the' pooled platelet concentrate. Other factors which determine the quality of a product, e.g. residual leukocyte count, plasma content, additive solution or storage period may be even more important. The focus of the debate should be shifted. It is much more needed to further improve the overall quality of PCs and to optimize treatment of thrombocytopenic patients than to concentrate on a single-edged view on just the preparation method. In the second part of this review we compare the product types from the donor's point of view. If PCs which are equally safe and effective can be obtained by various methods, ethics and the safety of the healthy volunteer donor tips the scales. The decision on the use of a particular product type should take into account all aspects of efficacy, side effects and availability of the product as well as the donor's perspective and the commitment to maximize the use of the valuable whole-blood donation.

Schwender, J. D., et al. (2005). "Minimally invasive transforaminal lumbar interbody fusion (TLIF): technical feasibility and initial results." J Spinal Disord Tech 18 Suppl: S1-6.

Forty-nine patients underwent minimally invasive transforaminal lumbar interbody fusion (TLIF) from October 2001 to August 2002 (minimum 18-month follow-up). The diagnosis was degenerative disc disease with herniated nucleus pulposus (HNP) in 26, spondylolisthesis in 22, and a Chance-type seatbelt fracture in 1. The majority of cases (n = 45) were at L4-L5 or L5-S1. A paramedian, muscle-sparing approach was performed through a tubular retractor docked unilaterally on the facet joint. A total facetectomy was then conducted, exposing the disc space. Discectomy and endplate preparation were completed through the tube using customized surgical instruments. Structural support was achieved with allograft bone or interbody cages. Bone grafting was done with local autologous or allograft bone, augmented with recombinant human bone morphogenetic protein-2 in some cases. Bilateral percutaneous pedicle screw-rod placement was accomplished with the Sextant system. There were no conversions to open surgery. Operative time averaged 240 minutes. Estimated blood loss averaged 140 mL. Mean length of hospital stay was 1.9 days. All patients presenting with preoperative radiculopathy (n = 45) had resolution of symptoms postoperatively. Complications included two instances of screw malposition requiring screw repositioning and two cases of new radiculopathy postoperatively (one from graft dislodgement, the other from contralateral neuroforaminal stenosis). Narcotic use was discontinued 2-4 weeks postoperatively. Improvements in average Visual Analogue Pain Scale and Oswestry Disability Index (preoperative to last follow-up) scores were 7.2-2.1 and 46-14, respectively. At last follow-up, all patients had solid fusions by radiographic criteria. Results of this study indicate that minimally invasive TLIF is feasible and offers several potential advantages over traditional open techniques.

Seamon, J., et al. (2012). "The pathogenesis of nontraumatic osteonecrosis." Arthritis 2012: 601763.

Nontraumatic osteonecrosis continues to be a challenging problem causing debilitating major joint diseases. The etiology is multifactorial, but steroid- and alcohol-induced osteonecrosis contribute to more than two thirds of all cases with genetic risk factors playing an important role in many other cases, especially when they contribute to hypercoagulable states. While the exact mechanisms remain elusive, many new insights have emerged from research in the last decade that have given us a clearer picture of the pathogenesis of nontraumatic osteonecrosis of the femoral head. Progression to end stage osteonecrosis of the femoral head appears to be related to four main factors: interactions involving the differentiation pathway of osteoprogenitor cells that promote adipogenesis, decreased angiogenesis, direct suppression of osteogenic gene expression and proliferation of bone marrow stem cells, and genetic anomalies or other diseases that promote hypercoagulable states.

Shaked, Y., et al. (2009). "Contribution of granulocyte colony-stimulating factor to the acute mobilization of endothelial precursor cells by vascular disrupting agents." Cancer Res 69(19): 7524-7528.

Vascular disrupting agents (VDA) cause acute shutdown of abnormal established tumor vasculature, followed by massive intratumoral hypoxia and necrosis. However, a viable rim of tumor tissue invariably remains from which tumor regrowth rapidly resumes. We have recently shown that an acute systemic mobilization and homing of bone marrow-derived circulating endothelial precursor (CEP) cells could promote tumor regrowth following treatment with either a VDA or certain chemotherapy drugs. The molecular mediators of this systemic reactive host process are unknown. Here, we show that following treatment of mice with OXi-4503, a second-generation potent prodrug derivative of combretastatin-A4 phosphate, rapid increases in circulating plasma vascular endothelial growth factor, stromal derived factor-1 (SDF-1), and granulocyte colony-stimulating factor (G-CSF) levels are detected. With the aim of determining whether G-CSF is involved in VDA-induced CEP mobilization, mutant G-CSF-R(-/-) mice were treated with OXi-4503. We found that as opposed to wild-type controls, G-CSF-R(-/-) mice failed to mobilize CEPs or show induction of SDF-1 plasma levels. Furthermore, Lewis lung carcinomas grown in such mice treated with OXi-4503 showed greater levels of necrosis compared with tumors treated in wild-type mice. Evidence for rapid elevations in circulating plasma G-CSF, vascular endothelial growth factor, and SDF-1 were also observed in patients with VDA (combretastatin-A4 phosphate)-treated cancer. These results highlight the possible effect of drug-induced G-CSF on tumor regrowth following certain cytotoxic drug therapies, in this case using a VDA, and hence G-CSF as a possible therapeutic target.

Shintani, S., et al. (2001). "Augmentation of postnatal neovascularization with autologous bone marrow transplantation." Circulation 103(6): 897-903.

BACKGROUND: Endothelial progenitor cells (EPCs) have been identified in adult human peripheral blood. Because circulating EPCs should originate from bone marrow (BM), we examined whether BM mononuclear cells (BM-MNCs) can give rise to functional EPCs and whether transplantation of autologous BM-MNCs might augment angiogenesis and collateral vessel formation in a rabbit model of hindlimb ischemia. METHODS AND RESULTS: Rabbit BM-MNCs were isolated by centrifugation through a Histopaque density gradient and cultured on fibronectin. EPCs developed from BM-MNCs in vitro, as assessed by acetylated LDL incorporation, nitric oxide (NO) release, and expression of von Willebrand factor and lectin binding. Unilateral hindlimb ischemia was surgically induced in rabbits (n=8), and fluorescence-labeled autologous BM-MNCs were transplanted into the ischemic tissues. Two weeks after transplantation, fluorescence microscopy revealed that transplanted cells were incorporated into the capillary network among preserved skeletal myocytes. In contrast, transplanted autologous BM-fibroblasts did not participate in EC capillary network formation (n=5). Then, in an additional 27 rabbits, saline (control; n=8), autologous BM-MNCs (n=13; 6.9+/-2.2x10(6) cells/animal), or BM-fibroblasts (n=6; 6.5+/-1.5x10(6) cells/animal) were injected into the ischemic tissues at postoperative day 7. Four weeks after transplantation, the BM-MNC-transplanted group had more angiographically detectable collateral vessels (angiographic score: 1.5+/-0.34 versus 0.94+/-0.26 and 1.1+/-0.14; P:<0.05), a higher capillary density (23+/-5.8 versus 10+/-1.9 and 11+/-0.8 per field; P:<0.001), and a greater laser Doppler blood perfusion index (505+/-155 versus 361+/-35 and 358+/-22 U; P:<0.05) than the control and BM-fibroblast-transplanted groups. CONCLUSIONS: Direct local transplantation of autologous BM-MNCs seems to be a useful strategy for therapeutic neovascularization in ischemic tissues in adults, consistent with "therapeutic vasculogenesis."

Siemionow, K. B. and G. F. Muschler (2011). Principles of Bone Fusion. Rothman-Simeone The Spine. H. N. Herkowitz, S. R. Garfin, F. J. Eismont, G. R. Bell and R. A. Balderston. Philadelphia, PA, Elsevier Saunders. 2: 1130-1158.

Singh, K., et al. (2006). "Use of recombinant human bone morphogenetic protein-2 as an adjunct in posterolateral lumbar spine fusion: a prospective CT-scan analysis at one and two years." J Spinal Disord Tech 19(6): 416-423.

INTRODUCTION: This study determines whether recombinant human bone morphogenetic protein-2 (rhBMP-2) (12 mg at the rate of 1.5 mg/mL) delivered on an absorbable collagen sponge with an added bulking agent can increase posterolateral lumbar spine fusion success rates and decrease time for fusion with autogenous bone grafts. METHOD: A prospective, single institution, clinical case-matched, radiographic, cohort study was undertaken. A total of 52 patients underwent posterolateral lumbar arthrodesis with pedicle screw instrumentation. The experimental group (n=41) underwent placement of Iliac crest bone graft (ICBG) with InFUSE (12 mg/level at the rate of 1.5 mg/mL). The control group (n=11) consisted of sex-matched patients, consecutively collected over the same time period with an instrumented posterolateral arthrodesis and ICBG placed in the intertransverse space. OUTCOME MEASURES: Thin-cut (2 mm) axial, coronal, and sagittal reconstructions were blindly evaluated for evidence of bridging bone and cortication of the fusion mass by 3 separate reviewers. Fusions were graded and an overall score was given to the quality of the fusion mass. RESULTS: Fifty patients (ICBG alone n=11; ICBG/rhBMP-2 n=39) were available for CT evaluation at 2-year follow-up. An overall 97% (68/70 levels; Definite+Probably Fused) fusion rate in the rhBMP-2 group was achieved as compared to the 77% fusion rate (17/22 levels) in the ICBG alone group (P<0.05). In the rhBMP-2 group, 92% of the patients (36/39 patients) received an overall excellent subjective fusion rating as compared to 27% (3/11) in the control group (P<0.05). There was no computed tomographic evidence of soft-tissue ossification, dural ossification, or laminar bone regrowth in any patient. CONCLUSIONS: The adjunctive use of rhBMP-2 and ICBG seems to be safe and results in significantly larger and more consistent posterolateral fusion masses.

Smith, S. E. (2008). Applications of concentrated autologous adult stem cells for instrumented spinal fusion: A report of 4 cases. Longmont, CO, Front Range Orthopedics.

Soltan, M., et al. (2009). "Bone marrow: orchestrated cells, cytokines, and growth factors for bone regeneration." Implant Dent 18(2): 132-141.

Bone regeneration requires an orchestrated interaction between various cells and other biological components. The synthesis of bone matrix with the release of cellular cytokines and growth factors facilitates and regulates cell growth. This leads to the maturation of bone that can support functional implants. Bone-marrow aspirate is a rich source of cells, cytokines, and growth factors needed for bone formation. Harvesting the marrow from the anterior iliac crest is a simple, safe, and cost-effective procedure. Mixing it with a resorbable scaffold and transplanting it to a site can predictably enhance bone regeneration. This article explores the anatomy of the bone marrow and describes the necessary elements for successful bone grafts, such as cells, bone matrix, and cellular regulators (both soluble and insoluble).

Steinberg, M. (2000). "The advantages of core decompression for treating avascular necrosis." The University of Pennsylvania Orthopaedic Journal 13: 84-88.

Strauer, B. E., et al. (2005). "Regeneration of human infarcted heart muscle by intracoronary autologous bone marrow cell transplantation in chronic coronary artery disease: the IACT Study." J Am Coll Cardiol 46(9): 1651-1658.

OBJECTIVES: Stem cell therapy may be useful in chronic myocardial infarction (MI); this is conceivable, but not yet demonstrated in humans. BACKGROUND: After acute MI, bone marrow-derived cells improve cardiac function. METHODS: We treated 18 consecutive patients with chronic MI (5 months to 8.5 years old) by the intracoronary transplantation of autologous bone marrow mononuclear cells and compared them with a representative control group without cell therapy. RESULTS: After three months, in the transplantation group, infarct size was reduced by 30% and global left ventricular ejection fraction (+15%) and infarction wall movement velocity (+57%) increased significantly, whereas in the control group no significant changes were observed in infarct size, left ventricular ejection fraction, or wall movement velocity of infarcted area. Percutaneous transluminal coronary angioplasty alone had no effect on left ventricular function. After bone marrow cell transplantation, there was an improvement of maximum oxygen uptake (VO2max, +11%) and of regional 18F-fluor-desoxy-glucose uptake into infarct tissue (+15%). CONCLUSIONS: These results demonstrate that functional and metabolic regeneration of infarcted and chronically avital tissue can be realized in humans by bone marrow mononuclear cell transplantation.

Strauss, R., et al. (2012). "Regulation of stem cell plasticity: mechanisms and relevance to tissue biology and cancer." Mol Ther 20(5): 887-897.

Embryonic stem cells (ESCs) are associated with a high degree of plasticity, which allows them to self-renew and differentiate into every somatic cell. During differentiation, ESCs follow a hierarchically organized pattern towards tissue specificity, which ultimately results in permanent cell cycle arrest and a loss of cellular plasticity. In contrast to their normal somatic counterparts, cancer cells retain elevated levels of plasticity that include switches between epithelial and mesenchymal phenotypes. Transitions between these cell stages have lately been linked to the reacquisition of stem cell features during cellular reprogramming and dedifferentiation in normal and neoplastic cells. In this review, we discuss the key factors and their interplay that is needed to regain a stem cell stage with a particular emphasis put on the impact of cell cycle regulation. Apart from mechanistic insights into the emerging fundamental processes of stem cell plasticity and capacity to transdifferentiate, we also highlight implications of these concepts for tissue biology, tumorigenesis, and cancer therapy.

Street, J., et al. (2002). "Vascular endothelial growth factor stimulates bone repair by promoting angiogenesis and bone turnover." Proc Natl Acad Sci U S A 99(15): 9656-9661.

Several growth factors are expressed in distinct temporal and spatial patterns during fracture repair. Of these, vascular endothelial growth factor, VEGF, is of particular interest because of its ability to induce neovascularization (angiogenesis). To determine whether VEGF is required for bone repair, we inhibited VEGF activity during secondary bone healing via a cartilage intermediate (endochondral ossification) and during direct bone repair (intramembranous ossification) in a novel mouse model. Treatment of mice with a soluble, neutralizing VEGF receptor decreased angiogenesis, bone formation, and callus mineralization in femoral fractures. Inhibition of VEGF also dramatically inhibited healing of a tibial cortical bone defect, consistent with our discovery of a direct autocrine role for VEGF in osteoblast differentiation. In separate experiments, exogenous VEGF enhanced blood vessel formation, ossification, and new bone (callus) maturation in mouse femur fractures, and promoted bony bridging of a rabbit radius segmental gap defect. Our results at specific time points during the course of healing underscore the role of VEGF in endochondral vs. intramembranous ossification, as well as skeletal development vs. bone repair. The responses to exogenous VEGF observed in two distinct model systems and species indicate that a slow-release formulation of VEGF, applied locally at the site of bone damage, may prove to be an effective therapy to promote human bone repair.

Sugimura, R., et al. (2012). "Noncanonical Wnt signaling maintains hematopoietic stem cells in the niche." Cell 150(2): 351-365.

Wnt signaling is involved in self-renewal and maintenance of hematopoietic stem cells (HSCs); however, the particular role of noncanonical Wnt signaling in regulating HSCs in vivo is largely unknown. Here, we show Flamingo (Fmi) and Frizzled (Fz) 8, members of noncanonical Wnt signaling, both express in and functionally maintain quiescent long-term HSCs. Fmi regulates Fz8 distribution at the interface between HSCs and N-cadherin(+) osteoblasts (N-cad(+)OBs that enrich osteoprogenitors) in the niche. We further found that N-cad(+)OBs predominantly express noncanonical Wnt ligands and inhibitors of canonical Wnt signaling under homeostasis. Under stress, noncanonical Wnt signaling is attenuated and canonical Wnt signaling is enhanced in activation of HSCs. Mechanistically, noncanonical Wnt signaling mediated by Fz8 suppresses the Ca(2+)-NFAT- IFNgamma pathway, directly or indirectly through the CDC42-CK1alpha complex and also antagonizes canonical Wnt signaling in HSCs. Taken together, our findings demonstrate that noncanonical Wnt signaling maintains quiescent long-term HSCs through Fmi and Fz8 interaction in the niche.

Tabata, Y. (2003). "Tissue regeneration based on growth factor release." Tissue Eng 9 Suppl 1: S5-15.

Tissue engineering is an emerging biomedical field intended to assist the regeneration of body tissue defects too large to self-repair as well as to substitute for the biological functions of damaged and injured organs by using cells with proliferative and differentiative potential. In addition to basic research on such cells, it is undoubtedly indispensable for successful tissue engineering to create an artificial environment enabling cells to induce tissue regeneration. Such an environment can be achieved by making use of a scaffold for cell proliferation and differentiation and for growth factors, as well as their combination. Growth factors are often required to promote tissue regeneration, as they can induce angiogenesis, which supplies oxygen and nutrients to cells transplanted for organ substitution to maintain their biological functions. However, the biological effects of growth factors cannot always be expected because of their poor in vivo stability, unless a drug delivery system is contrived. In this article, tissue regeneration based on the release of growth factors is reviewed to emphasize the significance of drug delivery systems in tissue engineering.

Tabbara, I. A., et al. (2002). "Allogeneic hematopoietic stem cell transplantation: complications and results." Arch Intern Med 162(14): 1558-1566.

Acute complications such as veno-occlusive disease of the liver, acute and chronic graft-vs-host disease (GVHD), and infectious conditions remain major obstacles for the success of allogeneic hematopoietic stem cell transplantation (HSCT). Progress in allogeneic HSCT depends on several factors, including the adequate prevention and management of associated complications, advances in the conventional management of diseases currently treated with allogeneic HSCT, expansion of the donor pool, selective control of GVHD, development of more effective preparative regimens to eradicate the neoplastic cell population, characterization of a new generation of hematopoietic growth factors and cytokines, and development of newer techniques for ex vivo manipulation of stem cells. Hematopoietic growth factor-mobilized donor progenitor cells collected from peripheral blood have been shown to be associated with rapid hematopoietic engraftment without an increase in the incidence of acute GVHD compared with allogeneic bone marrow transplantation. Implementation of this approach will enhance donor acceptance, eliminate the risk of general anesthesia, decrease cost, and reduce the risk of infectious complications by reducing the duration of neutropenia. Nonmyeloablative allogeneic stem cell transplantation represents a novel treatment approach that may lead to reduced toxic effects and extended use of this treatment in older patients and in those with malignant and nonmalignant disorders. However, GVHD and disease recurrence remain a challenge. Promising results have been reported in patients with refractory hematologic malignancies and in metastatic renal cell cancer. Because late complications are commonly encountered in patients receiving allogeneic HSCT, lifelong observation is needed.

Taguchi, A., et al. (2004). "Circulating CD34-positive cells provide an index of cerebrovascular function." Circulation 109(24): 2972-2975.

BACKGROUND: Increasing evidence points to a role for circulating endothelial progenitor cells, including populations of CD34- and CD133-positive cells present in peripheral blood, in maintenance of the vasculature and neovascularization. Immature populations, including CD34-positive cells, have been shown to contribute to vascular homeostasis, not only as a pool of endothelial progenitor cells but also as a source of growth/angiogenesis factors at ischemic loci. We hypothesized that diminished numbers of circulating immature cells might impair such physiological and reparative processes, potentially contributing to cerebrovascular dysfunction. METHODS AND RESULTS: The level of circulating immature cells, CD34-, CD133-, CD117-, and CD135-positive cells, in patients with a history of atherothrombotic cerebral ischemic events was analyzed to assess possible correlations with the degree of carotid atherosclerosis and number of cerebral infarctions. There was a strong inverse correlation between numbers of circulating CD34- and CD133-positive cells and cerebral infarction. In contrast, there was no correlation between the degree of atherosclerosis and populations of circulating immature cells. Analysis of patients with cerebral artery occlusion revealed a significant positive correlation between circulating CD34- and CD133-positive cells and regional blood flow in areas of chronic hypoperfusion. CONCLUSIONS: These results suggest a possible contribution of circulating CD34- and CD133-positive cells in maintenance of the cerebral circulation in settings of ischemic stress. Our data demonstrate the utility of a simple and precise method to quantify circulating CD34-positive cells, the latter providing a marker of cerebrovascular function.

Taguchi, A., et al. (2008). "Circulating CD34-positive cells provide a marker of vascular risk associated with cognitive impairment." J Cereb Blood Flow Metab 28(3): 445-449.

Maintenance of uninterrupted cerebral circulation is critical for neural homeostasis. The level of circulating CD34-positive (CD34(+)) cells has been suggested as an index of cerebrovascular health, although its relationship with cognitive function has not yet been defined. In a group of individuals with cognitive impairment, the level of circulating CD34(+) cells was quantified and correlated with clinical diagnoses. Compared with normal subjects, a significant decrease in circulating CD34(+) cells was observed in patients with vascular-type cognitive impairment, although no significant change was observed in patients with Alzheimer's-type cognitive impairment who had no evidence of cerebral ischemia. The level of cognitive impairment was inversely correlated with numbers of circulating CD34(+) cells in patients with vascular-type cognitive impairment, but not Alzheimer's type. We propose that the level of circulating CD34(+) cells provides a marker of vascular risk associated with cognitive impairment, and that differences in the pathobiology of Alzheimer's- and vascular-type cognitive impairment may be mirrored in levels of circulating CD34(+) cells in these patient populations.

Taguchi, A., et al. (2009). "Circulating CD34-positive cells have prognostic value for neurologic function in patients with past cerebral infarction." J Cereb Blood Flow Metab 29(1): 34-38.

Increasing evidence points to a role for circulating endothelial progenitors, including populations of CD34-positive (CD34(+)) cells present in peripheral blood, in vascular homeostasis and neovascularization. In this report, circulating CD34(+) cells in individuals with a history of cerebral infarction were correlated with changes in neurologic function over a period of 1 year. Patients with decreased levels of CD34(+) cells displayed significant worsening in neurologic function, evaluated by the Barthel Index and Clinical Dementia Rating. These results support the hypothesis that levels of circulating CD34(+) cells have prognostic value for neural function, consistent with their potential role in maintaining cerebral circulation.

Taguchi, A., et al. (2004). "Administration of CD34+ cells after stroke enhances neurogenesis via angiogenesis in a mouse model." J Clin Invest 114(3): 330-338.

Thrombo-occlusive cerebrovascular disease resulting in stroke and permanent neuronal loss is an important cause of morbidity and mortality. Because of the unique properties of cerebral vasculature and the limited reparative capability of neuronal tissue, it has been difficult to devise effective neuroprotective therapies in cerebral ischemia. Our results demonstrate that systemic administration of human cord blood-derived CD34(+) cells to immunocompromised mice subjected to stroke 48 hours earlier induces neovascularization in the ischemic zone and provides a favorable environment for neuronal regeneration. Endogenous neurogenesis, suppressed by an antiangiogenic agent, is accelerated as a result of enhanced migration of neuronal progenitor cells to the damaged area, followed by their maturation and functional recovery. Our data suggest an essential role for CD34(+) cells in promoting directly or indirectly an environment conducive to neovascularization of ischemic brain so that neuronal regeneration can proceed.

Taguchi, A., et al. (2011). "Reduced ischemic brain injury by partial rejuvenation of bone marrow cells in aged rats." J Cereb Blood Flow Metab 31(3): 855-867.

Circulating bone marrow-derived immature cells, including endothelial progenitor cells, have been implicated in homeostasis of the microvasculature. Decreased levels of circulating endothelial progenitor cells, associated with aging and/or cardiovascular risk factors, correlate with poor clinical outcomes in a range of cardiovascular diseases. Herein, we transplanted bone marrow cells from young stroke-prone spontaneously hypertensive rats (SHR-SP) into aged SHR-SP, the latter not exposed to radiation or chemotherapy. Analysis of recipient peripheral blood 28 days after transplantation revealed that 5% of circulating blood cells were of donor origin. Cerebral infarction was induced on day 30 posttransplantation. Animals transplanted with bone marrow from young SHR-SP displayed an increase in density of the microvasculature in the periinfarction zone, reduced ischemic brain damage and improved neurologic function. In vitro analysis revealed enhanced activation of endothelial nitric oxide synthase and reduced activation p38 microtubule-associated protein (MAP) kinase, the latter associated with endothelial apoptosis, in cultures exposed to bone marrow-derived mononuclear cells from young animals versus cells from aged counterparts. Our findings indicate that partial rejuvenation of bone marrow from aged rats with cells from young animals enhances the response to ischemic injury, potentially at the level of endothelial/vascular activation, providing insight into a novel approach ameliorate chronic vascular diseases.

Taichman, R. S. (2005). "Blood and bone: two tissues whose fates are intertwined to create the hematopoietic stem-cell niche." Blood 105(7): 2631-2639.

The mechanisms of bone and blood formation have traditionally been viewed as distinct, unrelated processes, but compelling evidence suggests that they are intertwined. Based on observations that hematopoietic precursors reside close to endosteal surfaces, it was hypothesized that osteoblasts play a central role in hematopoiesis, and it has been shown that osteoblasts produce many factors essential for the survival, renewal, and maturation of hematopoietic stem cells (HSCs). Preceding these observations are studies demonstrating that the disruption or perturbation of normal osteoblastic function has a profound and central role in defining the operational structure of the HSC niche. These observations provide a glimpse of the dimensions and ramifications of HSC-osteoblast interactions. Although more research is required to secure a broader grasp of the molecular mechanisms that govern blood and bone biology, the central role for osteoblasts in hematopoietic stem cell regulation is reviewed herein from the perspectives of (1) historical context; (2) the role of the osteoblast in supporting stem cell survival, proliferation, and maintenance; (3) the participation, if any, of osteoblasts in the creation of a stem cell niche; (4) the molecules that mediate HSC-osteoblast interactions; (5) the role of osteoblasts in stem cell transplantation; and (6) possible future directions for investigation.

Taichman, R. S., et al. (1996). "Human osteoblasts support human hematopoietic progenitor cells in vitro bone marrow cultures." Blood 87(2): 518-524.

Hematopoietic stem cell differentiation occurs in direct proximity to osteoblasts within the bone marrow cavity. Despite this striking affiliation, surprisingly little is known about the precise cellular and molecular impact of osteoblasts on the bone marrow microenvironment. Recently, we showed that human osteoblasts produce a variety of cytokine mRNAs including granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and interleukin-6. We examined here the ability of osteoblasts to support the development of hematopoietic colonies from progenitors as well the ability to maintain long-term culture-initiating cells (LTC-IC) in vitro. Examination of the hematopoietic cells recovered after 2 weeks of culture showed that osteoblasts support the maintenance of immature hematopoietic phenotypes. In methylcellulose assays, osteoblasts stimulate the development of hematopoietic colonies to a level at least 10-fold over controls from progenitor cells. Using limiting dilutional bone marrow cultures, we observed an activity produced by osteoblasts resulting in an threefold to fourfold expansion of human LTC-IC and progenitor cells in vitro. Thus, the presence of hematopoietic stem cells in close proximity to endosteal surfaces in vivo may be due in part to a requirement for osteoblast-derived products.

Taichman, R. S., et al. (2010). "Prospective identification and skeletal localization of cells capable of multilineage differentiation in vivo." Stem Cells Dev 19(10): 1557-1570.

A prospective in vivo assay was used to identify cells with potential for multiple lineage differentiation. With this assay, it was first determined that the 5-fluorouracil resistant cells capable of osseous tissue formation in vivo also migrated toward stromal derived factor-1 (SDF-1) in vitro. In parallel, an isolation method based on fluorescence-activated cell sorting was employed to identify a very small cell embryonic-like Lin-/Sca-1+CD45- cell that with as few as 500 cells was capable of forming bone-like structures in vivo. Differential marrow fractionation studies determined that the majority of the Lin-Sca-1+CD45- cells reside in the subendosteal regions of marrow. To determine whether these cells were capable of differentiating into multiple lineages, stromal cells harvested from Col2.3 Delta TK mice were implanted with a gelatin sponge into SCID mice to generate thymidine kinase sensitive ossicles. At 1.5 months, 2,000 green fluorescent protein (GFP)+ Lin-Sca-1+CD45- cells were injected into the ossicles. At harvest, colocalization of GFP-expressing cells with antibodies to the osteoblast-specific marker Runx-2 and the adipocyte marker PPAP gamma were observed. Based on the ability of the noncultured cells to differentiate into multiple mesenchymal lineages in vivo and the ability to generate osseous tissues at low density, we propose that this population fulfills many of the characteristics of mesenchymal stem cells.

Tateishi-Yuyama, E., et al. (2002). "Therapeutic angiogenesis for patients with limb ischaemia by autologous transplantation of bone-marrow cells: a pilot study and a randomised controlled trial." Lancet 360(9331): 427-435.

BACKGROUND: Preclinical studies have established that implantation of bone marrow-mononuclear cells, including endothelial progenitor cells, into ischaemic limbs increases collateral vessel formation. We investigated efficacy and safety of autologous implantation of bone marrow-mononuclear cells in patients with ischaemic limbs because of peripheral arterial disease. METHODS: We first did a pilot study, in which 25 patients (group A) with unilateral ischaemia of the leg were injected with bone marrow-mononuclear cells into the gastrocnemius of the ischaemic limb and with saline into the less ischaemic limb. We then recruited 22 patients (group B) with bilateral leg ischaemia, who were randomly injected with bone marrow-mononuclear cells in one leg and peripheral blood-mononuclear cells in the other as a control. Primary outcomes were safety and feasibility of treatment, based on ankle-brachial index (ABI) and rest pain, and analysis was per protocol. FINDINGS: Two patients were excluded from group B after randomisation. At 4 weeks in group B patients, ABI was significantly improved in legs injected with bone marrow-mononuclear cells compared with those injected with peripheral blood-mononuclear cells (difference 0.09 [95% CI 0.06-0.11]; p<0.0001). Similar improvements were seen for transcutaneous oxygen pressure (13 [9-17]; p<0.0001), rest pain (-0.85 [-1.6 to -0.12]; p=0.025), and pain-free walking time (1.2 [0.7-1.7]; p=0.0001). These improvements were sustained at 24 weeks. Similar improvements were seen in group A patients. Two patients in group A died after myocardial infarction unrelated to treatment. INTERPRETATION: Autologous implantation of bone marrow-mononuclear cells could be safe and effective for achievement of therapeutic angiogenesis, because of the natural ability of marrow cells to supply endothelial progenitor cells and to secrete various angiogenic factors or cytokines.

Team, T. E. (2013). EndNote for iPad Getting Started Guide, Thomson Reuters.

Tepper, O. M., et al. (2005). "Adult vasculogenesis occurs through in situ recruitment, proliferation, and tubulization of circulating bone marrow-derived cells." Blood 105(3): 1068-1077.

Ischemia is a known stimulus for vascular growth. Bone marrow (BM)-derived endothelial progenitor cells (EPCs) are believed to contribute to new blood vessel growth, but the mechanism for this contribution is unknown. To elucidate how BM cells are able to form new blood vessels, a novel murine model of soft tissue ischemia was developed in lethally irradiated mice with BM reconstituted from either tie2/lacZ or ROSA/green fluorescent protein (GFP) mice (n = 24). BM-derived EPCs were recruited to ischemic tissue within 72 hours, and the extent of recruitment was directly proportional to the degree of tissue ischemia. At 7 days, there were persistently elevated levels of vascular endothelial growth factor (VEGF) (2.5-fold) and circulating VEGF receptor-2/CD11(-) (flk-1(+)/CD11(-)) cells (18-fold) which correlated with increased numbers of BM-derived EPCs within ischemic tissue. The cells were initially located extravascularly as proliferative clusters. By day 14, these clusters coalesced into vascular cords, which became functional vessels by day 21. In vitro examination of human EPCs from healthy volunteers (n = 10) confirmed that EPC proliferation, adhesion, and chemotaxis were all significantly stimulated in hypoxic conditions. We conclude that BM-derived cells produce new blood vessels via localized recruitment, proliferation, and differentiation of circulating cells in a sequence of events markedly different from existing paradigms of angiogenesis.

Theise, N. D. (2010). "Stem cell plasticity: recapping the decade, mapping the future." Exp Hematol 38(7): 529-539.

In slightly more than a decade of stem cell plasticity research, 24 peer-reviewed articles have demonstrated plasticity across organ and/or embryonic lineage boundaries at the single-cell level, with only 1 article showing negative results. These data, taken together with data about reversibility of gene restrictions that have also accumulated during the same period, indicate that postnatal cells, even "terminally differentiated" ones, have a degree of plasticity not appreciated previously. This review looks back at the four known pathways of cell plasticity and at previously described "plasticity principles" of Genomic Completeness, Cellular Uncertainty, Stochasticity of Cell Origin and Fate, relating these to issues of experimental design and discourse that are key to understanding and evaluating plasticity data. Although the physiologic roles played by such plasticity may still be debated, the manipulations of these phenomena for therapeutic or industrial purposes should finally be considered ripe for exploration. For the future, plasticity, indeed all stem cell biology, must be considered as part of a larger web of cell-to-cell and cell-to-matrix interactions that function fully only at the tissue level; thus, the success of stem cell biology necessarily must involve assembling data from cell and molecular biology research into systems of interactions that might be reasonably called "tissue biology." Interdisciplinary collaborations with complexity and chaos theorists, using mathematical/computer modeling of cell behaviors, will be vital to fully exploring stem cell behaviors in the coming decades.

Theise, N. D. and M. d'Inverno (2004). "Understanding cell lineages as complex adaptive systems." Blood Cells Mol Dis 32(1): 17-20.

Stem cells may be considered complex reactive systems because of their vast number in a living system, their reactive nature, and the influence of local environmental factors (such as the state of neighboring cells, tissue matrix, stem cell physiological processes) on their behavior. In such systems, emergent global behavior arises through the multitude of local interactions among the cell agents. Approaching hematopoietic and other stem cell lineages from this perspective have critical ramifications on current thinking relating to the plasticity of these lineage systems, the modeling of stem cell systems, and the interpretation of clinical data regarding many diseases within such models.

Thomas, E. D., et al. (1957). "Intravenous infusion of bone marrow in patients receiving radiation and chemotherapy." N Engl J Med 257(11): 491-496.

Till, J. E. and C. E. Mc (1961). "A direct measurement of the radiation sensitivity of normal mouse bone marrow cells." Radiat Res 14: 213-222.

Timmins, N. E., et al. (2012). "Closed system isolation and scalable expansion of human placental mesenchymal stem cells." Biotechnol Bioeng.

Mesenchymal stem cells (MSC) are emerging as a leading cellular therapy for a number of diseases. However, for such treatments to become available as a routine therapeutic option, efficient and cost-effective means for industrial manufacture of MSC are required. At present, clinical grade MSC are manufactured through a process of manual cell culture in specialized cGMP facilities. This process is open, extremely labor intensive, costly, and impractical for anything more than a small number of patients. While it has been shown that MSC can be cultivated in stirred bioreactor systems using microcarriers, providing a route to process scale-up, the degree of numerical expansion achieved has generally been limited. Furthermore, little attention has been given to the issue of primary cell isolation from complex tissues such as placenta. In this article we describe the initial development of a closed process for bulk isolation of MSC from human placenta, and subsequent cultivation on microcarriers in scalable single-use bioreactor systems. Based on our initial data, we estimate that a single placenta may be sufficient to produce over 7,000 doses of therapeutic MSC using a large-scale process. Biotechnol. Bioeng. (c) 2012 Wiley Periodicals, Inc.

Tondreau, T., et al. (2005). "Mesenchymal stem cells derived from CD133-positive cells in mobilized peripheral blood and cord blood: proliferation, Oct4 expression, and plasticity." Stem Cells 23(8): 1105-1112.

In this study, we used a common procedure to assess the potential of mobilized peripheral blood (MPB) and umbilical cord blood (UCB) as sources of mesenchymal stem cells (MSCs) in comparison with bone marrow (BM). We tested three methods: plastic adhesion supplemented with 5% of BM-MSC conditioned medium, unsupplemented plastic adhesion, and selection of CD133-positive cells. MSCs derived from MPB or UCB are identified by their positive expression of mesenchymal (SH2, SH3) and negative expression of hematopoietic markers (CD14, CD34, CD45, HLA-DR). We observed that the CD133-positive cell fraction contains more MSCs with high proliferative potential. Placed in appropriate conditions, these cells proved their capacity to differentiate into adipocytes, osteocytes, chondrocytes, and neuronal/glial cells. MPB- and UCB-MSCs express Oct4, a transcriptional binding factor present in undifferentiated cells with high proliferative capacity. The selection of CD133-positive cells enabled us to obtain a homogeneous population of MSCs from UCB and MPB. These sources may have a major clinical importance thanks to their easy accessibility.

Tosh, D. and J. M. Slack (2002). "How cells change their phenotype." Nat Rev Mol Cell Biol 3(3): 187-194.

Recent attention has focused on the remarkable ability of adult stem cells to produce differentiated cells from embryologically unrelated tissues. This phenomenon is an example of metaplasia and shows that embryological commitments can be reversed or erased under certain circumstances. In some cases, even fully differentiated cells can change their phenotype (transdifferentiation). This review examines recently discovered cases of metaplasia, and speculates on the potential molecular and cellular mechanisms that underlie the switches, and their significance to developmental biology and medicine.

Tow, B. P., et al. (2007). "Disc regeneration: a glimpse of the future." Clin Neurosurg 54: 122-128.

The normal IVD clinically acts to support and dissipate loads while permitting multiaxial motions of the spine. Its demanding mechanical function is provided by a well-defined microstructural organization and biochemical composition. IVD degeneration is a complex process that disrupts this well-defined organization and biochemical balance. One hallmark of IVD degeneration is the loss of proteoglycan and water in the NP. Because of the central role of proteoglycans in the function of the IVD, restoration of normal proteoglycan production may be critical. Many different biological strategies have been developed, including the use of cells, scaffolds, and molecules. The molecules used to treat disc degeneration include anticatabolics and growth factors, which may influence the cell proliferation rate and phenotypic expression of the cells. Delivery of the molecules may include direct injection into the disc and also in vivo and ex vivo gene therapy using a viral vector. Although many of the in vitro and in vivo studies have exhibited promise in reversing the observed changes of disc degeneration, the unanswered question is whether these efforts will translate to the relief of patients' symptoms, the most common of which is back pain.

Tremoleda, J. L., et al. (2012). "Assessment of a preclinical model for studying the survival and engraftment of human stem cell derived osteogenic cell populations following orthotopic implantation." J Musculoskelet Neuronal Interact 12(4): 241-253.

INTRODUCTION: Preclinical studies with osteoprogenitor cells derived from human embryonic stem cells (hESC) do not lead to substantial bone regeneration in vivo. The degree of survival following implantation might play a role in their long term efficiency. We investigated the initial engraftment of hESCs-derived cells during two weeks post-implantation and compared it to such response for adult bone marrow stromal cells (hBMSC)-derived osteoprogenitor cells. METHODS: hBMSC and H9-hES cells pre-treated with osteogenic factors were implanted into a calvarial defect in both adult WT and nude rats. At days 7 and 14 post-implantation, samples were analysed for persistence of implanted cells, initiation of regeneration of host bone, angiogenesis and apoptosis. RESULTS: At day 7, hESC and hBMSC were detected within defects in both rat strains. By day 14 human cells were only detected in immune-deficient rats whilst still maintaining an osteoblastic phenotype and engendered a significant increase in bone formation. In WT animals, the participation of implanted cells was very limited due to their poor survival. CONCLUSION: This study demonstrates the ability of hESC and hBMSC derived osteoprogenitor cells to survive transplantation, to engraft and to develop an osteogenic phenotype during the early stage following implantation, validating the appropriate preclinical model.

Trueta, J. (1963). "The role of the vessels in osteogenesis." J Bone Joint Surg 45B(2): 402-418.

Turan, R. G., et al. (2011). "Improved functional activity of bone marrow derived circulating progenitor cells after intra coronary freshly isolated bone marrow cells transplantation in patients with ischemic heart disease." Stem Cell Rev 7(3): 646-656.

OBJECTIVES: There is growing evidence that intracoronary autologous bone marrow cells transplantation (BMCs-Tx) in patients with chronic myocardial infarction beneficially affects postinfarction remodelling. In this randomized controlled study we analyzed the influence of intracoronary autologous freshly isolated bone marrow cells transplantation by use of point of care system on cardiac function and on the functional activity of bone marrow derived circulating progenitor cells (BM-CPCs) in patients with ischemic heart disease (IHD). METHODS: 56 patients with IHD were randomized to either received freshly isolated BMC-Tx or a control group that did not receive cell therapy. The functional activity of BM-CPCs in peripheral blood (PB) was measured by migration assay and colony forming unit assay pre- and 3, 6 as well as 12 months after procedure. Global ejection fraction (EF) and infarct size area were determined by left ventriculography. RESULTS: Intracoronary transplantation of autologous freshly isolated BMCs led to a significant reduction of infarct size and an increase of global EF as well as infarct wall movement velocity after 3 and 12 months follow-up compared to control group. The colony-forming capacity of BM-CPCs significantly increased 3, 6 and 12 months after cell therapy compared to pre BMCs-Tx and control group (CFU-E: p < 0.001, CFU-GM: p < 0.001). Likewise, we found significant increase of migratory response to stromal cell-derived factor 1 (SDF-1) and vascular endothelial growth factor (VEGF) after cell therapy compared to pre BMCs-Tx (SDF-1: p < 0.001, VEGF: p < 0.001) and to control (SDF-1: p < 0.001, VEGF: p < 0.001). There was no significant difference of migratory- and colony forming capacity between pre- and 3, 6, 12 months after coronary angiography in control group without cell therapy. CONCLUSIONS: Intracoronary transplantation of autologous freshly isolated BMCs by use of point of care system may lead to improvement of BM-CPCs functional activity in peripheral blood, which might increase the regenerative potency in patients with IHD.

Turan, R. G., et al. (2011). "Enhanced mobilisation of the bone marrow derived circulating progenitor cells by intracoronary freshly isolated bone marrow cells transplantation in patients with acute myocardial infarction." J Cell Mol Med.

Autologous bone marrow cell transplantation (BMCs-Tx) is a promising novel option for treatment of cardiovascular disease. We analyzed in a randomized controlled study the influence of the intracoronary autologous freshly isolated BMCs-Tx on the mobilisation of BM-CPCs in patients with acute myocardial infarction (AMI). 62 patients with AMI were randomized to either freshly isolated BMCs-Tx or to a control group without cell therapy. Peripheral blood (PB) concentrations of CD34/45(+) and CD133/45(+) circulating progenitor cells were measured by flow cytometry in 42 AMI patients with cell therapy as well as in 20 AMI patients without cell therapy as a control group on days 1, 3, 5, 7, 8 and 3, 6 as well as 12 months after AMI. Global ejection fraction (EF) and the size of infarct area were determined by left ventriculography. We observed in patients with freshly isolated BMCs-Tx at 3 and 12 months follow up a significant reduction of infarct size and increase of global EF as well as infarct wall movement velocity. The mobilisation of CD34/45(+) and CD133/45(+) BM-CPCs significantly increased with a peak on day 7 as compared to baseline after AMI in both groups (CD34/45(+) : p<0.001, CD133/45(+) : p<0.001). Moreover, this significant mobilisation of BM-CPCs existed 3, 6 and 12 months after cell therapy compared to day 1 after AMI. In control group there were no significant differences of CD34/45(+) and CD133/45(+) BM-CPCs mobilisation between day 1 and 3, 6, 12 months after AMI. Intracoronary transplantation of autologous freshly isolated BMCs by use of point of care system in patients with AMI may enhance and prolong the mobilisation of CD34/45(+) and CD133/45(+) BM-CPCs in PB and this might increase the regenerative potency after AMI.

Turan, R. G., et al. (2011). "Improvement of cardiac function by intracoronary freshly isolated bone marrow cells transplantation in patients with acute myocardial infarction." Circ J 75(3): 683-691.

BACKGROUND: We analyzed in the present study the influence of intracoronary autologous freshly isolated bone marrow cells transplantation (BMCs-Tx) on cardiac function in patients with acute myocardial infarction (AMI). METHODS AND RESULTS: The 32 patients with AMI were enrolled in this prospective nonrandomized study to either freshly isolated BMC-Tx or to a control group without cell therapy. Global left ventricular ejection fraction (LVEF) and the size of infarct area were determined by left ventriculography. We observed in patients with autologous freshly isolated BMCs-Tx at 6 months follow up a significant reduction of infarct size as compared to control group. Moreover, we found a significant increase of LVEF as well as infarct wall movement velocity at 6 months follow up in cell therapy group as compared to control group. In the control group there was no significant difference of LVEF, infarct size and infarct wall movement velocity between baseline and 6 months after AMI. CONCLUSIONS: These results demonstrate for the first time that intracoronary transplantation of autologous freshly isolated BMCs by use of a point of care system is safe, and may lead to improvement of cardiac function in patients with AMI.

Turan, R. G., et al. (2011). "Improved mobilization of the CD34(+) and CD133(+) bone marrow-derived circulating progenitor cells by freshly isolated intracoronary bone marrow cell transplantation in patients with ischemic heart disease." Stem Cells Dev 20(9): 1491-1501.

Cell therapy is a promising novel option for treatment of cardiovascular disease. Because the role of bone marrow-derived circulating progenitor cells (BM-CPCs) after cell therapy is less clear, we analyzed in this randomized, controlled study the influence of intracoronary autologous freshly isolated bone marrow cell transplantation (BMC-Tx) by using a point-of-care system on cardiac function and on the mobilization of BM-CPCs in patients with ischemic heart disease (IHD). Fifty-six patients with IHD were randomized to either receive freshly isolated BMC-Tx or a control group that did not receive cell therapy. Peripheral blood concentrations of CD34/45(+) and CD133/45(+) CPCs were measured by flow cytometry pre-, immediately post-, and at 3, 6, and 12 months postprocedure in both groups. Global ejection fraction and the size of infarct area were determined by left ventriculography. We observed in patients with IHD after intracoronary transplantation of autologous freshly isolated BMCs-Tx at 3 and 12 months follow-up a significant reduction of the size of infarct area and increase of global ejection fraction as well as infarct wall movement velocity. The mobilization of CD34/45(+) and CD133/45(+) BM-CPCs significantly increased at 3, 6, and 12 months after cell therapy when compared with baseline in patients with IHD, although no significant changes were observed between pre- and immediately postintracoronary cell therapy administration. In the control group without cell therapy, there was no significant difference of CD34/45(+) and CD133/45(+) BM-CPCs mobilization between pre- and at 3, 6, and 12 months postcoronary angiography. Intracoronary transplantation of autologous freshly isolated BMCs by using a point-of-care system in patients with IHD may enhance and prolong the mobilization of CD34/45(+) and CD133/45(+) BM-CPCs in peripheral blood and this might increase the regenerative potency in IHD.

Turan, R. G., et al. (2011). "Impaired mobilization of CD133(+) bone marrow-derived circulating progenitor cells with an increased number of diseased coronary arteries in ischemic heart disease patients with diabetes." Circ J 75(11): 2635-2641.

BACKGROUND: The influence of the number of diseased coronary arteries on the mobilization of CD133/45(+) bone marrow-derived circulating progenitor cells (BM-CPCs) in peripheral blood (PB) in patients with ischemic heart disease (IHD) was analyzed. METHODS AND RESULTS: Mobilization of CD133/45(+) BM-CPCs by flow cytometry was measured in 120 patients with coronary 1 vessel (IHD1, n=40), coronary 2 vessel (IHD2, n=40), and coronary 3 vessel disease (IHD3, n=40), and in a control group (n=40). The mobilization of CD133/45(+) BM-CPCs was significantly reduced in patients with IHD compared to the control group (P<0.001). The mobilization of CD133/45(+) BM-CPCs was impaired in patients with IHD3 compared to IHD1 (P<0.001) and to IHD2 (P<0.001). But there was no significant difference in mobilization of CD133/45(+) BM-CPCs between the patients with IHD2 and IHD1 (P=0.35). Moreover, we found significantly reduced CD133/45(+) cell mobilization in patients with a high SYNTAX-Score (SS) compared to a low SS (P<0.001) and an intermediate SS (P<0.001). In subgroup analyzes, we observed a significantly negative correlation between levels of hemoglobin A(1c) and the mobilization of CD133/45(+) BM-CPCs (P=0.001, r=-0.6). CONCLUSIONS: The mobilization of CD133/45(+) BM-CPCs in PB is impaired in patients with IHD. This impairment might augment with increased number of diseased coronary arteries. Moreover, mobilization of CD133/45(+) BM-CPCs in ischemic tissue is further impaired by diabetes in patients with IHD.

Uchida, N., et al. (1994). "Rapid and sustained hematopoietic recovery in lethally irradiated mice transplanted with purified Thy-1.1lo Lin-Sca-1+ hematopoietic stem cells." Blood 83(12): 3758-3779.

Hematopoietic stem cells (HSCs) are believed to play a critical role in the sustained repopulation of all blood cells after bone marrow transplantation (BMT). However, understanding the role of HSCs versus other hematopoietic cells in the quantitative reconstitution of various blood cell types has awaited methods to isolate HSCs. A candidate population of mouse HSCs, Thy-1.1lo Lin-Sca-1+ cells, was isolated several years ago and, recently, this population has been shown to be the only population of BM cells that contains HSCs in C57BL/Ka-Thy-1.1 mice. As few as 100 of these cells can radioprotect 95% to 100% of irradiated mice, resulting long-term multilineage reconstitution. In this study, we examined the reconstitution potential of irradiated mice transplanted with purified Thy-1.1lo Lin-Sca-1+ BM cells. Donor-derived peripheral blood (PB) white blood cells were detected as early as day 9 or 10 when 100 to 1,000 Thy-1.1lo Lin-Sca-1+ cells were used, with minor dose-dependent differences. The reappearance of platelets by day 14 and thereafter was also seen at all HSC doses (100 to 1,000 cells), with a slight dose-dependence. All studied HSC doses also allowed RBC levels to recover, although at the 100 cell dose a delay in hematocrit recovery was observed at day 14. When irradiated mice were transplanted with 500 Thy-1.1lo Lin-Sca-1+ cells compared with 1 x 10(6) BM cells (the equivalent amount of cells that contain 500 Thy-1.1lo Lin-Sca-1+ cells as well as progenitor and mature cells), very little difference in the kinetics of recovery of PB, white blood cells, platelets, and hematocrit was observed. Surprisingly, even when 200 Thy1.1lo Lin-Sca-1+ cells were mixed with 4 x 10(5) Sca-1- BM cells in a competitive repopulation assay, most of the early (days 11 and 14) PB myeloid cells were derived from the HSC genotype, indicating the superiority of the Thy-1.1lo Lin-Sca-1+ cells over Sca-1- cells even in the early phases of myeloid reconstitution. Within the Thy-1.1lo Lin-Sca-1+ population, the Rhodamine 123 (Rh123)hi subset dominates in PB myeloid reconstitution at 10 to 14 days, only to be overtaken by the Rh123lo subset at 3 weeks and thereafter. These findings indicate that HSCs can account for the early phase of hematopoietic recovery, as well as sustained hematopoiesis, and raise questions about the role of non-HSC BM populations in the setting of BMT.

Vaughan, J. (1981). "Osteogenesis and haematopoiesis." Lancet 2(8238): 133-136.

Veerappan, R., et al. (2007). "Splenic rupture in a patient with plasma cell myeloma following G-CSF/GM-CSF administration for stem cell transplantation and review of the literature." Bone Marrow Transplant 40(4): 361-364.

Recipients of granulocyte-colony stimulating factor/granulocyte macrophage-colony stimulating factor are not only individuals with underlying disorders, but also healthy donors undergoing peripheral blood progenitor cell (PBPC) mobilization. In addition to the known adverse effects associated with G-CSF, complications such as splenic rupture have also been reported. A review of the English literature, with addition of a patient with plasma cell myeloma, reveals that splenic rupture occurs not only in patients with underlying disease, but also in healthy PBPC donors. Although the cause of splenic rupture does not appear to be associated with any specific condition, physicians should be alerted to the possibility of this potentially fatal complication in individuals receiving G-CSF therapy.

Velazquez, O. C. (2007). "Angiogenesis and vasculogenesis: inducing the growth of new blood vessels and wound healing by stimulation of bone marrow-derived progenitor cell mobilization and homing." J Vasc Surg 45 Suppl A: A39-47.

During embryonic development, the vasculature is among the first organs to form and is in charge of maintaining metabolic homeostasis by supplying oxygen and nutrients and removing waste products. As one would expect, blood vessels are critical not only for organ growth in the embryo but also for repair of wounded tissue in the adult. An imbalance in angiogenesis (a time-honored term that globally refers to the growth of new blood vessels) contributes to the pathogenesis of numerous malignant, inflammatory, ischemic, infectious, immune, and wound-healing disorders. This review focuses on the central role of the growth of new blood vessels in ischemic and diabetic wound healing and defines the most current nomenclature that describes the neovascularization process in wounds. There are now two well-defined, distinct, yet interrelated processes for the formation of postnatal new blood vessels, angiogenesis, and vasculogenesis. Reviewed are recent new data on vasculogenesis that promise to advance the field of wound healing.

von Bahr, L., et al. (2012). "Analysis of tissues following mesenchymal stromal cell therapy in humans indicates limited long-term engraftment and no ectopic tissue formation." Stem Cells 30(7): 1575-1578.

Mesenchymal stromal cells (MSCs) are explored as a novel treatment for a variety of medical conditions. Their fate after infusion is unclear, and long-term safety regarding malignant transformation and ectopic tissue formation has not been addressed in patients. We examined autopsy material from 18 patients who had received human leukocyte antigen (HLA)-mismatched MSCs, and 108 tissue samples from 15 patients were examined by PCR. No signs of ectopic tissue formation or malignant tumors of MSC-donor origin were found on macroscopic or histological examination. MSC donor DNA was detected in one or several tissues including lungs, lymph nodes, and intestine in eight patients at levels from 1/100 to <1/1,000. Detection of MSC donor DNA was negatively correlated with time from infusion to sample collection, as DNA was detected from nine of 13 MSC infusions given within 50 days before sampling but from only two of eight infusions given earlier. There was no correlation between MSC engraftment and treatment response. We conclude that MSCs appear to mediate their function through a "hit and run" mechanism. The lack of sustained engraftment limits the long-term risks of MSC therapy. STEM CELLS2012;30:1575-1578.

Vunjak-Novakovic, G., et al. (2010). "Challenges in cardiac tissue engineering." Tissue Eng Part B Rev 16(2): 169-187.

Cardiac tissue engineering aims to create functional tissue constructs that can reestablish the structure and function of injured myocardium. Engineered constructs can also serve as high-fidelity models for studies of cardiac development and disease. In a general case, the biological potential of the cell-the actual "tissue engineer"-is mobilized by providing highly controllable three-dimensional environments that can mediate cell differentiation and functional assembly. For cardiac regeneration, some of the key requirements that need to be met are the selection of a human cell source, establishment of cardiac tissue matrix, electromechanical cell coupling, robust and stable contractile function, and functional vascularization. We review here the potential and challenges of cardiac tissue engineering for developing therapies that could prevent or reverse heart failure.

Wagers, A. J. (2012). "The stem cell niche in regenerative medicine." Cell Stem Cell 10(4): 362-369.

Stem cells are fundamental units for achieving regenerative therapies, which leads naturally to a theoretical and experimental focus on these cells for therapeutic screening and intervention. A growing body of data in many tissue systems indicates that stem cell function is critically influenced by extrinsic signals derived from the microenvironment, or "niche." In this vein, the stem cell niche represents a significant, and largely untapped, entry point for therapeutic modulation of stem cell behavior. This Perspective will discuss how the niche influences stem cells in homeostasis, in the progression of degenerative and malignant diseases, and in therapeutic strategies for tissue repair.

Wagers, A. J., et al. (2002). "Little evidence for developmental plasticity of adult hematopoietic stem cells." Science 297(5590): 2256-2259.

To rigorously test the in vivo cell fate specificity of bone marrow (BM) hematopoietic stem cells (HSCs), we generated chimeric animals by transplantation of a single green fluorescent protein (GFP)-marked HSC into lethally irradiated nontransgenic recipients. Single HSCs robustly reconstituted peripheral blood leukocytes in these animals, but did not contribute appreciably to nonhematopoietic tissues, including brain, kidney, gut, liver, and muscle. Similarly, in GFP+:GFP- parabiotic mice, we found substantial chimerism of hematopoietic but not nonhematopoietic cells. These data indicate that "transdifferentiation" of circulating HSCs and/or their progeny is an extremely rare event, if it occurs at all.

Wagers, A. J. and I. L. Weissman (2004). "Plasticity of adult stem cells." Cell 116(5): 639-648.

Recent years have seen much excitement over the possibility that adult mammalian stem cells may be capable of differentiating across tissue lineage boundaries, and as such may represent novel, accessible, and very versatile effectors of therapeutic tissue regeneration. Yet studies proposing such "plasticity" of adult somatic stem cells remain controversial, and in general, existing evidence suggests that in vivo such unexpected transformations are exceedingly rare and in some cases can be accounted for by equally unexpected alternative explanations.

Wan, M., et al. (2012). "Injury-Activated Transforming Growth Factor beta Controls Mobilization of Mesenchymal Stem Cells for Tissue Remodeling." Stem Cells 30(11): 2498-2511.

Upon secretion, transforming growth factor beta (TGFbeta) is maintained in a sequestered state in extracellular matrix as a latent form. The latent TGFbeta is considered as a molecular sensor that releases active TGFbeta in response to the perturbations of the extracellular matrix at the situations of mechanical stress, wound repair, tissue injury, and inflammation. The biological implication of the temporal discontinuity of TGFbeta storage in the matrix and its activation is obscure. Here, using several animal models in which latent TGFbeta is activated in vascular matrix in response to injury of arteries, we show that active TGFbeta controls the mobilization and recruitment of mesenchymal stem cells (MSCs) to participate in tissue repair and remodeling. MSCs were mobilized into the peripheral blood in response to vascular injury and recruited to the injured sites where they gave rise to both endothelial cells for re-endothelialization and myofibroblastic cells to form thick neointima. TGFbetas were activated in the vascular matrix in both rat and mouse models of mechanical injury of arteries. Importantly, the active TGFbeta released from the injured vessels is essential to induce the migration of MSCs, and cascade expression of monocyte chemotactic protein-1 stimulated by TGFbeta amplifies the signal for migration. Moreover, sustained high levels of active TGFbeta were observed in peripheral blood, and at the same time points following injury, Sca1(+) CD29(+) CD11b(-) CD45(-) MSCs, in which 91% are nestin(+) cells, were mobilized to peripheral blood and recruited to the remodeling arteries. Intravenously injection of recombinant active TGFbeta1 in uninjured mice rapidly mobilized MSCs into circulation. Furthermore, inhibitor of TGFbeta type I receptor blocked the mobilization and recruitment of MSCs to the injured arteries. Thus, TGFbeta is an injury-activated messenger essential for the mobilization and recruitment of MSCs to participate in tissue repair/remodeling. STEM CELLS2012;30:2498-2511.

Wang, L. D. and A. J. Wagers (2011). "Dynamic niches in the origination and differentiation of haematopoietic stem cells." Nat Rev Mol Cell Biol 12(10): 643-655.

Haematopoietic stem cells (HSCs) are multipotent, self-renewing progenitors that generate all mature blood cells. HSC function is tightly controlled to maintain haematopoietic homeostasis, and this regulation relies on specialized cells and factors that constitute the haematopoietic 'niche', or microenvironment. Recent discoveries, aided in part by technological advances in in vivo imaging, have engendered a new appreciation for the dynamic nature of the niche, identifying novel cellular and acellular niche components and uncovering fluctuations in the relative importance of these components over time. These new insights significantly improve our understanding of haematopoiesis and raise fundamental questions about what truly constitutes a stem cell niche.

Wang, Y. X. and M. A. Rudnicki (2011). "Satellite cells, the engines of muscle repair." Nat Rev Mol Cell Biol.

Satellite cells are a heterogeneous population of stem and progenitor cells that are required for the growth, maintenance and regeneration of skeletal muscle. The transcription factors paired-box 3 (PAX3) and PAX7 have essential and overlapping roles in myogenesis. PAX3 acts to specify embryonic muscle precursors, whereas PAX7 enforces the satellite cell myogenic programme while maintaining the undifferentiated state. Recent experiments have suggested that PAX7 is dispensable in adult satellite cells. However, these findings are controversial, and the issue remains unresolved.

Wang, Y. Z., et al. (2011). "Concise review: Quiescent and active states of endogenous adult neural stem cells: identification and characterization." Stem Cells 29(6): 907-912.

The adult mammalian central nervous system (CNS) lacks the capacity for regeneration, making it a highly sought-after topic for researchers. The identification of neural stem cells (NSCs) in the adult CNS wiped out a long-held dogma that the adult brain contains a set number of neurons and is incapable of replacing them. The discovery of adult NSCs (aNSCs) stoked the fire for researchers who dream of brain self-repair. Unfortunately, the quiescent nature and limited plasticity of aNSCs diminish their regenerative potential. Recent studies evaluating aNSC plasticity under pathological conditions indicate that a switch from quiescent to active aNSCs in neurogenic regions plays an important role in both repairing the damaged tissue and preserving progenitor pools. Here, we summarize the most recent findings and present questions about characterizing the active and quiescent aNSCs in major neurogenic regions, and factors for maintaining their active and quiescent states, hoping to outline an emerging view for promoting the endogenous aNSC-based regeneration.

Wells, W. A. (2002). "Is transdifferentiation in trouble?" J Cell Biol 157(1): 15-18.

Spectacular examples of transdifferentiation--such as brain cells turning to blood and blood to brain--have given way to sneaking suspicions about artifacts in culture, fusion, and clonality. Could cell fates be relatively fixed after all?

Wen, P., et al. (2011). Stem Cell Niche. Regenerative Medicine from Protocol to Patient. G. Steinhoff. Dordrecht, Springer: 81-101.

Wohlrab, F. and U. Henoch (1988). "[The life and work of Carl Weigert (1845-1904) in Leipzig 1878-1885]." Zentralbl Allg Pathol 134(8): 743-751.

Coming from Breslau, together with J. Cohnheim (1839-1884), Carl Weigert arrived at the University of Leipzig in 1878. Here, in 1879, he was appointed extraordinary professor at the Department of Pathology. Apart from his growing commitment to autopsy and teaching, due to progressive illness of Cohnheim and the resulting involvement in management of the Department. Weigert studied topical issues of pathology, such as coagulation necrosis and pathogenesis of tuberculosis. His studies into histological staining techniques (principle of elective staining, mordant staining, staining of myelin sheaths) as well as into microtome techniques proved essential to progress in pathology and bacteriology. Weigert left the Leipzig Department of Pathology at the end of March 1885, after the Medical Faculty had failed to appoint him as the successor to Cohnheim. On the 1st of April, 1885, Weigert accepted the position of Director of Senckenberg's Pathological Institute at Frankfurt/Main.

Wojakowski, W., et al. (2011). "Circulating very small embryonic-like stem cells in cardiovascular disease." J Cardiovasc Transl Res 4(2): 138-144.

Very small embryonic-like cells (VSELs) are a population of stem cells residing in the bone marrow (BM) and several organs, which undergo mobilization into peripheral blood (PB) following acute myocardial infarction and stroke. These cells express markers of pluripotent stem cells (PSCs), such as Oct-4, Nanog, and SSEA-1, as well as early cardiac, endothelial, and neural tissue developmental markers. VSELs can be effectively isolated from the BM, umbilical cord blood, and PB. Peripheral blood and BM-derived VSELs can be expanded in co-culture with C2C12 myoblast feeder layer and undergo differentiation into cells from all three germ layers, including cardiomyocytes and vascular endothelial cells. Isolation of VSLEs using fluorescence-activated cell sorting multiparameter live cell sorting system is dependent on gating strategy based on their small size and expression of PSC and absence of hematopoietic lineage markers. VSELs express early cardiac and endothelial lineages markers (GATA-4, Nkx2.5/Csx, VE-cadherin, and von Willebrand factor), SDF-1 chemokine receptor CXCR4, and undergo rapid mobilization in acute MI and ischemic stroke. Experiments in mice showed differentiation of BM-derived VSELs into cardiac myocytes and effectiveness of expanded and pre-differentiated VSLEs in improvement of left ventricular ejection fraction after myocardial infarction.

Wojakowski, W., et al. (2004). "Mobilization of CD34/CXCR4+, CD34/CD117+, c-met+ stem cells, and mononuclear cells expressing early cardiac, muscle, and endothelial markers into peripheral blood in patients with acute myocardial infarction." Circulation 110(20): 3213-3220.

BACKGROUND: Adult stem cells can contribute to myocardial regeneration after ischemic injury. Bone marrow and skeletal muscles contain a population of CXCR4+ cells expressing genes specific for muscle progenitor cells that can be mobilized into the peripheral blood. The aims of the study were (1) to confirm the presence of early tissue-committed cells expressing cardiac, muscle, and endothelial markers in populations of mononuclear cells in peripheral blood and (2) to assess the dynamics and magnitude of the mobilization of CD34+, CD117+, CXCR4+, c-met+, CD34/CD117+, and CD34/CXCR4+ stem cells into peripheral blood in relation to inflammatory and hematopoietic cytokines in patients with ST-segment-elevation acute myocardial infarction (STEMI). METHODS AND RESULTS: Fifty-six patients with STEMI (<12 hours), 39 with stable angina, and 20 healthy control subjects were enrolled. Real-time reverse transcription-polymerase chain reaction (RT-PCR) was used for detection of tissue-specific markers. The number of the cells was assessed by use of a flow cytometer on admission, after 24 hours, and after 7 days. RT-PCR revealed increased expression of mRNA (up to 3.5-fold increase) for specific cardiac (GATA4, MEF2C, Nkx2.5/Csx), muscle (Myf5, Myogenin, MyoD), and endothelial (VE-cadherin, von Willebrand factor) markers in peripheral blood mononuclear cells. The number of CD34/CXCR4+ and CD34/CD117+ and c-met+ stem cells in peripheral blood was significantly higher in STEMI patients than in stable angina and healthy subjects, peaking on admission, without further significant increase after 24 hours and 7 days. CONCLUSIONS: The study demonstrates in the setting of STEMI a marked mobilization of mononuclear cells expressing specific cardiac, muscle, and endothelial markers as well as CD34/CXCR4+ and CD34/CD117+ and c-met+ stem cells and shows that stromal cell-derived factor-1 is an important factor influencing the mobilization.

Wuchter, P., et al. (2011). Mesenchymal Stem Cells: An Oversimplified Nomenclature for Extremely Heterogeneous Progenitors. Regenerative Medicine: From Protocol to Patient. G. Steinhoff. Dordrecht, Springer: 377-395.

Mesenchymal stem cells (MSC) are plastic-adherent fibroblast-like cells

that can readily be isolated from various tissues and expanded in vitro. Per definitionem,

they are able to differentiate into bone, cartilage and adipose tissue.

Different

preparative protocols have been shown to yield MSC-like cell lines from starting

materials as diverse as bone marrow, fat tissue, umbilical cord blood and peripheral

blood. However, MSC are still ill-defined by physical, phenotypic and functional

properties. Furthermore, the composition of cell preparations and the differentiation

potential changes in the course of long-term culture expansion. There is an

urgent need for the development of molecular markers and universal criteria for

quality control of the starting cell populations as well as for the cell products after

expansion. Nevertheless, MSC have already found their way into a vast number of

clinical studies addressing a broad variety of diseases. Even though there is no convincing

evidence that MSC are involved in the process of tissue repair by transdifferentiation,

they probably contribute to the repair process by immunomodulatory

effects and interaction with other cell types.

Xiang, Y., et al. (2007). "Ex vivo expansion and pluripotential differentiation of cryopreserved human bone marrow mesenchymal stem cells." J Zhejiang Univ Sci B 8(2): 136-146.

This study is aimed at investigating the potentials of ex vivo expansion and pluri-differentiation of cryopreservation of adult human bone marrow mesenchymal stem cells (hMSCs) into chondrocytes, adipocytes and neurocytes. Cryopreserved hMSCs were resuscitated and cultured for 15 passages, and then induced into chondrocytes, adipocytes and neurocytes with corresponding induction medium. The induced cells were observed for morphological properties and detected for expressions of type II collagen, triglyceride or neuron-specific enolase and nestin. The result showed that the resuscitated cells could differentiate into chondrocytes after exposure to transforming growth factor beta(1) (TGF-beta(1)), insulin-like growth factor I (IGF-I) and vitamin C (V(C)), and uniformly changed morphologically from a spindle-like fibroblastic appearance to a polygonal shape in three weeks. The induced cells were heterochromatic to safranin O and expressed cartilage matrix-procollagenal (II) mRNA. The resuscitated cells cultured in induction medium consisting of dexamethasone, 3-isobutyl-1-methylxanthine, indomethacin and IGF-I showed adipogenesis, and lipid vacuoles accumulation was detectable after 21 d. The resuscitated hMSCs were also induced into neurocytes and expressed nestin and neuron specific endolase (NSE) that were special surface markers associated with neural cells at different stage. This study suggested that the resuscitated hMSCs should be still a population of pluripotential cells and that it could be used for establishing an abundant hMSC reservoir for further experiment and treatment of various clinical diseases.

Yamada, S., et al. (2009). "Distribution of transfused bone marrow cells following endothelial damage of a cortical artery." Journal of Cerebral Blood Flow & Metabolism 29: S376-S377.

Yasuhara, S., et al. (2010). "Efficacy of bone marrow mononuclear cells to promote bone regeneration compared with isolated CD34+ cells from the same volume of aspirate." Artif Organs 34(7): 594-599.

Autologous bone marrow mononuclear cell (BMMNC) transplantation is currently an emerging clinical treatment in the orthopedic as well as cardiovascular fields. It is believed that the therapeutic effect of the BMMNCs is due to neovascularization enhanced by the CD34(+) cells contained therein, which include endothelial progenitor cells. However, isolation of the CD34(+) cell fraction for clinical application has many disadvantages such as cost and invasiveness related to cell mobilization with cytokine. To investigate whether a purification step is in fact necessary for bone regeneration, we separated BMMNCs, CD34(+), and CD34(-) cells from the same initial volume of rabbit bone marrow aspirates. We then transplanted them back into a femoral bone defect of the same rabbit together with atelocollagen gel and basic fibroblast growth factor (bFGF) and evaluated neovascularization and bone regeneration up to 8 weeks after transplantation. The greatest potential for neovascularization and bone regeneration medicated by cells from the same volume of bone marrow aspirate was found in the BMMNC group. Although purified CD34(+) cells might be an ideal cell source, BMMNCs could be a practical and feasible cell source for bone regeneration in present clinical settings with limited cost, availability of materials, and technical issues for transplantation.

Yoder, M. C. (2009). Overview of Stem Cell Biology. Hematology: Basic Principles and Practice. R. Hoffman, E. J. J. Benz, S. J. Shattil et al. Philadelphia, PA, Churchill Livingstone Elsevier: 187-199.

Yoshihara, T., et al. (2008). "Increase in circulating CD34-positive cells in patients with angiographic evidence of moyamoya-like vessels." J Cereb Blood Flow Metab 28(6): 1086-1089.

Increasing evidence points to a role for circulating endothelial progenitor cells, including populations of CD34-positive (CD34(+)) cells, in maintenance of cerebral blood flow. In this study, we investigated the link between the level of circulating CD34(+) cells and neovascularization at ischemic brain. Compared with control subjects, a remarkable increase of circulating CD34(+) cells was observed in patients with angiographic moyamoya vessels, although no significant change was observed in patients with major cerebral artery occlusion (or severe stenosis) but without moyamoya vessels. Our results suggest that the increased level of CD34(+) cells associated with ischemic stress is correlated with neovascularization at human ischemic brain.

Yu, L. and C. A. Hales (2011). "Effect of chemokine receptor CXCR4 on hypoxia-induced pulmonary hypertension and vascular remodeling in rats." Respir Res 12: 21.

BACKGROUND: CXCR4 is the receptor for chemokine CXCL12 and reportedly plays an important role in systemic vascular repair and remodeling, but the role of CXCR4 in development of pulmonary hypertension and vascular remodeling has not been fully understood. METHODS: In this study we investigated the role of CXCR4 in the development of pulmonary hypertension and vascular remodeling by using a CXCR4 inhibitor AMD3100 and by electroporation of CXCR4 shRNA into bone marrow cells and then transplantation of the bone marrow cells into rats. RESULTS: We found that the CXCR4 inhibitor significantly decreased chronic hypoxia-induced pulmonary hypertension and vascular remodeling in rats and, most importantly, we found that the rats that were transplanted with the bone marrow cells electroporated with CXCR4 shRNA had significantly lower mean pulmonary pressure (mPAP), ratio of right ventricular weight to left ventricular plus septal weight (RV/(LV+S)) and wall thickness of pulmonary artery induced by chronic hypoxia as compared with control rats. CONCLUSIONS: The hypothesis that CXCR4 is critical in hypoxic pulmonary hypertension in rats has been demonstrated. The present study not only has shown an inhibitory effect caused by systemic inhibition of CXCR4 activity on pulmonary hypertension, but more importantly also has revealed that specific inhibition of the CXCR4 in bone marrow cells can reduce pulmonary hypertension and vascular remodeling via decreasing bone marrow derived cell recruitment to the lung in hypoxia. This study suggests a novel therapeutic approach for pulmonary hypertension by inhibiting bone marrow derived cell recruitment.

Zhang, W., et al. (2009). "Role of soluble epoxide hydrolase in post-ischemic angiogenesis." Journal of Cerebral Blood Flow & Metabolism(29): S378-379.

Zhang, Z. L., et al. (2009). "Therapeutic potential of non-adherent BM-derived mesenchymal stem cells in tissue regeneration." Bone Marrow Transplant 43(1): 69-81.

We demonstrated that non-adherent BM cells (NA-BMCs) can be expanded in suspension and give rise to multiple mesenchymal phenotypes including fibroblastic, osteoblastic, chondrocytic and adipocytic as well as glial cell lineages in vitro using the 'pour-off' BMC culture method. Mesenchymal stem cells (MSCs) derived from NA-BMCs (NA-MSCs) from wild-type mice were transplanted into VDR gene knockout (VDR(-/-)) mice that had received a lethal dose of radiation. Results revealed that NA-MSC can be used to rescue lethally irradiated mice and become incorporated into a diverse range of tissues. After lethal dose irradiation, all untransplanted mice died within 2 weeks, whereas those transplanted with NA-MSCs were viable for at least 3 months. Transplantation rescued these mice by reconstructing a hematopoietic system and repairing other damaged tissues. WBC, RBC and platelet counts recovered to normal after 1 month, and VDR gene expression was found in various tissues of viable VDR(-/-) recipients. Adult BM harbors pluripotent NA-MSCs, which can migrate in vivo into multiple body organs. In an appropriate microenvironment, they can adhere, proliferate and differentiate into specialized cells of target tissues and thus function in damaged tissue regeneration and repair.

Zhong, W., et al. (2012). "In Vivo Comparison of the Bone Regeneration Capability of Human Bone Marrow Concentrates vs. Platelet-Rich Plasma." PLoS One 7(7): e40833.

BACKGROUND: Bone marrow aspirate concentrate (BMAC) including high densities of stem cells and progenitor cells may possess a stronger bone regenerative capability compared with Platelet-rich plasma (PRP), which contains enriched growth factors. The objective of this study was to evaluate the effects of human BMAC and PRP in combination with beta-tricalcium phosphate (beta-TCP) on promoting initial bone augmentation in an immunodeficient mouse model. METHODOLOGY/PRINCIPAL FINDINGS: BMAC and PRP were concentrated with an automated blood separator from the bone marrow and peripheral blood aspirates. beta-TCP particles were employed as a scaffold to carry cells. After cell counting and FACS characterization, three groups of nude mice (BMAC+TCP, PRP+TCP, and a TCP control) were implanted with graft materials for onlay placement on the cranium. Samples were harvested after 4 weeks, and serial sections were prepared. We observed the new bone on light microscopy and performed histomorphometric analysis. After centrifugation, the concentrations of nucleated cells and platelets in BMAC were increased by factors of 2.8+/-0.8 and 5.3+/-2.4, respectively, whereas leucocytes and platelets in PRP were increased by factors of 4.1+/-1.8 and 4.4+/-1.9, respectively. The concentrations of CD34-, CD271-, CD90-, CD105-, and CD146-positive cells were markedly increased in both BMAC and PRP. The percentage of new bone in the BMAC group (7.6+/-3.9%) and the PRP group (7.2+/-3.8%) were significantly higher than that of TCP group (2.7+/-1.4%). Significantly more bone cells in the new bone occurred in sites transplanted with BMAC (552+/-257) and PRP (491+/-211) compared to TCP alone (187+/-94). But the difference between the treatment groups was not significant. CONCLUSIONS/SIGNIFICANCE: Both human BMACs and PRP may provide therapeutic benefits in bone tissue engineering applications. These fractions possess a similar ability to enhance early-phase bone regeneration.

Zhu, B., et al. (2012). "CXCL12 Enhances Human Neural Progenitor Cell Survival Through a CXCR7- and CXCR4-Mediated Endocytotic Signaling Pathway." Stem Cells 30(11): 2571-2583.

Chemokine CXCL12 is widely expressed in the central nervous system and essential for the proper functioning of human neural progenitor cells (hNPCs). Although CXCL12 is known to function through its receptor CXCR4, recent data have suggested that CXCL12 binds to chemokine receptor CXCR7 with higher affinity than to CXCR4. However, little is known about the function of CXCR7 in hNPCs. Using a primary hNPC culture system, we demonstrated that CXCL12 promotes hNPC survival in the events of camptothecin-induced apoptosis or growth factor deprivation, and that this effect requires both CXCR7 and CXCR4. Through fluorescence-activated cell sorting analysis and immunocytochemistry, we determined that CXCR7 is mainly localized in the early endosome, while CXCR4 is more broadly expressed at the cell surface and on both early and recycling endosomes. Furthermore, we found that endocytosis is required for the prosurvival function of CXCL12. Using dual-color total internal reflection fluorescence microscopy and immunoprecipitation, we demonstrated that CXCR7 quickly trafficks to plasma membrane in mediating CXCL12 endocytosis and colocalizes with CXCR4 after CXCL12 treatment. Investigating the molecular mechanisms, we found that ERK1/2 endocytotic signaling pathway is essential for hNPC survival upon apoptotic challenges. Consistent with these findings, a significantly higher number of apoptotic NPCs were found in the developing brain of CXCR7 knockout mice. In conclusion, CXCL12 protects hNPCs from apoptotic challenges through CXCR7- and CXCR4-mediated endocytotic signaling. Since survival of hNPCs is important for neurogenesis, CXCR7 may become a new therapeutic target to properly regulate critical processes of brain development. STEM CELLS2012;30:2571-2583.

Ziv, Y., et al. (2006). "Immune cells contribute to the maintenance of neurogenesis and spatial learning abilities in adulthood." Nat Neurosci 9(2): 268-275.

Neurogenesis is known to take place in the adult brain. This work identifies T lymphocytes and microglia as being important to the maintenance of hippocampal neurogenesis and spatial learning abilities in adulthood. Hippocampal neurogenesis induced by an enriched environment was associated with the recruitment of T cells and the activation of microglia. In immune-deficient mice, hippocampal neurogenesis was markedly impaired and could not be enhanced by environmental enrichment, but was restored and boosted by T cells recognizing a specific CNS antigen. CNS-specific T cells were also found to be required for spatial learning and memory and for the expression of brain-derived neurotrophic factor in the dentate gyrus, implying that a common immune-associated mechanism underlies different aspects of hippocampal plasticity and cell renewal in the adult brain.

Zubair, A. C., et al. (2002). "Adult hematopoietic stem cell plasticity." Transfusion 42(8): 1096-1101.

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