The role of angiopoietins in the development of endothelial cells from cord blood CD34+ progenitors

Transplantation of human umbilical cord blood mononuclear cells promotes functional endometrium reconstruction via downregulating EMT in damaged endometrium

Introduction

Cell transplantation is an emerging and effective therapeutic approach for enhancing uterine adhesions caused by endometrial damage. Currently, human umbilical cord blood mononuclear cells (HUCBMCs) have been extensively for tissue and organ regeneration. However, their application in endometrial repair remains unexplored. Our investigation focuses on the utilization of HUCBMCs for treating endometrial injury.

Methods

The HUCBMCs were isolated from health umbilical cord blood, and co-cultured with the injured endometrial stromal cells and injured endometrial organoids. The cell proliferation and apoptosis were measured by cck8 assays and flow cytometry. Western blotting was used to detect the expression of PTEN, AKT and p-AKT. Immunofluorescence assay revealed expression levels of epithelial-mesenchymal transition (EMT) -related markers such as E-cadherin, N-cadherin, and TGF-β1. The endometrial thickness, fibrosis level, and glandular number were examined after the intravenous injection of HUCBMCs in mouse endometrial models. Immunohistochemistry was employed to assess changes in growth factors vascular endothelial growth factor (VEGF) and insulin-like growth factor 1 (IGF-1) as well as fibrosis markers α-SMA and COL1A1. Additionally, expressions of EMT-related proteins E-cadherin and N-cadherin were evaluated.

Results

HUCBMCs significantly improved the proliferation and reduced the apoptosis of damaged endometrial stromal cells (ESCs), accompanied by up-regulation of phospho-AKT expression. HUCBMCs increased endometrial thickness and glandular count while decreasing fibrosis and EMT-related markers in mouse endometrial models. Furthermore, EMT-related markers of ESCs and endometrial organoids were significantly decreased.

Conclusions

Our findings suggest that HUCBMCs plays a pivotal role in mitigating endometrial injury through the attenuation of fibrosis. HUCBMCs may exert a reverse effect on the EMT process during the endometrium reconstruction.

Fresh Umbilical Cord Blood-A Source of Multipotent Stem Cells, Collection, Banking, Cryopreservation, and Ethical Concerns

Umbilical cord blood (UCB) is a rich source of hematopoietic cells that can be used to replace bone marrow components. Many blood disorders and systemic illnesses are increasingly being treated with stem cells as regenerative medical therapy. Presently, collected blood has been stored in either public or private banks for allogenic or autologous transplantation. Using a specific keyword, we used the English language to search for relevant articles in SCOPUS and PubMed databases over time frame. According to our review, Asian countries are increasingly using UCB preservation for future use as regenerative medicine, and existing studies indicate that this trend will continue. This recent literature review explains the methodology of UCB collection, banking, and cryopreservation for future clinical use. Between 2010 and 2022, 10,054 UCB stem cell samples were effectively cryopreserved. Furthermore, we have discussed using Mesenchymal Stem Cells (MSCs) as transplant medicine, and its clinical applications. It is essential for healthcare personnel, particularly those working in labor rooms, to comprehend the protocols for collecting, transporting, and storing UCB. This review aims to provide a glimpse of the details about the UCB collection and banking processes, its benefits, and the use of UCB-derived stem cells in clinical practice, as well as the ethical concerns associated with UCB, all of which are important for healthcare professionals, particularly those working in maternity wards; namely, the obstetrician, neonatologist, and anyone involved in perinatal care. This article also highlights the practical and ethical concerns associated with private UCB banks, and the existence of public banks. UCB may continue to grow to assist healthcare teams worldwide in treating various metabolic, hematological, and immunodeficiency disorders.

Differential phenotype and behavior in culture of CD34 positive cells from peripheral blood and adipose tissue

The localization and quantification of endothelial progenitor cells (EPCs) are controversial. Circulating CD34 + cells in blood have been identified as EPCs and as biomarkers of cardiovascular disease. We discuss in this paper the current data describing differential phenotype and behavior in vitro of CD34 positive cells from the circulation and adipose tissue (AT). We also describe in brief our own findings from CD34 + cells isolated from leukopheresis cones derived from healthy platelet donors and from patients undergoing bariatric surgery. We conclude that CD34 + cells in blood and in AT are different in antigenic profile and behavior in culture. The findings described assert that CD34 + cells detected in blood previously identified as biomarkers of cardiovascular disease are predominantly HPCs rather than EPCs, and that true CD34 + EPCs can be readily identified and extracted from AT, supportive of the current evidence which suggests EPCs are resident in the tissue vasculature.

Effects of shear stress on differentiation of stem cells into endothelial cells

Stem cell transplantation is an appealing potential therapy for vascular diseases and an indispensable key step in vascular tissue engineering. Substantial effort has been made to differentiate stem cells toward vascular cell phenotypes, including endothelial cells (ECs) and smooth muscle cells. The microenvironment of vascular cells not only contains biochemical factors that influence differentiation but also exerts hemodynamic forces, such as shear stress and cyclic strain. More recently, studies have shown that shear stress can influence the differentiation of stem cells toward ECs. A deep understanding of the responses and underlying mechanisms involved in this process is essential for clinical translation. This review highlights current data supporting the role of shear stress in stem cell differentiation into ECs. Potential mechanisms and signaling cascades for transducing shear stress into a biological signal are proposed. Further study of stem cell responses to shear stress will be necessary to apply stem cells for pharmacological applications and cardiovascular implants in the realm of regenerative medicine.

Aliskiren Improved the Endothelial Repair Capacity of Endothelial Progenitor Cells from Patients with Hypertension via the Tie2/PI3k/Akt/eNOS Signalling Pathway

Background

Studies show that aliskiren exerts favourable effects not only on endothelial progenitor cells (EPCs) but also on endothelial function. However, the mechanism of the favourable effect of aliskiren on EPCs from patients with hypertension is unclear and remains to be further studied.

Methods

The object of this study was to investigate and assess the in vitro function of EPCs pretreated with aliskiren. After treated with aliskiren, the human EPCs were transplanted into a nude mouse model of carotid artery injury, and the in vivo reendothelialization of injured artery was estimated by staining denuded areas with Evans blue dye via tail vein injection.

Results

We found that aliskiren increased the in vitro migration, proliferation, and adhesion of EPCs from patients with hypertension in a dose-dependent manner and improved the reendothelialization capability of these EPCs. Furthermore, aliskiren increased the phosphorylation of Tie2, Akt, and eNOS. After the blockade of the Tie2 signalling pathway, the favourable effects of aliskiren on the in vitro function and in vivo reendothelialization capability of EPCs were suppressed.

Conclusions

This study demonstrates that aliskiren can improve the in vitro function and in vivo reendothelialization capability of EPCs from patients with hypertension via the activation of the Tie2/PI3k/Akt/eNOS signalling pathway. These findings further indicate that aliskiren is an effective pharmacological treatment for cell-based repair in hypertension-related vascular injury.

Soluble Tei2 fusion protein inhibits retinopathy of prematurity occurrence via regulation of the Ang/Tie2 pathway

The aim of the present study was to investigate the potential mechanism of retinopathy of prematurity (ROP) using an oxygen-induced retinopathy (OIR) mouse model. For experiments, mice were divided into either the OIR group or control group. Fluorescein isothiocyanate-dextran cardiac perfusion and stretched retina preparation were performed. The total retina area, area of instillation, density of microvascular network, area of new blood vessels, vein width and the tortuosity of arteries were measured. Next, mice were randomly assigned into the PBS, soluble TEK receptor tyrosine kinase (sTie2)-fusion protein (Fc), angiopoietin 1 (Ang1), ranibizumab, ranibizumab + sTie2-Fc and ranibizumab + Ang1 treatment groups. Following housing for 5 days, the body weight of each mouse was recorded. Mice in the OIR group presented smaller total retina area and larger area of instillation, larger area of new blood vessels, and higher microvascular network density compared with the control PBS group. Obvious retinal vein dilatation and arterial tortuosity were identified in the OIR group. The amount of endotheliocyte nuclei of new vessels beyond the inner limiting membrane was larger in the OIR group compared with the control group. Furthermore in the next set of experiments, a larger area of instillation, smaller area of new blood vessels and decreased amount of endotheliocyte nuclei of new vessels were observed in the sTie2-Fc group, Ang1 group, ranibizumab group, ranibizumab + sTie2-Fc group and ranibizumab + Ang1 group compared with the PBS group. Specifically, the ranibizumab + sTie2-Fc group and ranibizumab + Ang1 group demonstrated markedly reduced retina instillation area and microvascular network density in the instillation area. Total retina area and body weight following 10 days of the experiment for the ranibizumab group were significantly lower compared with other groups. In conclusion, the combined regulation of the Ang/Tie2 and the vascular endothelial growth factor (VEGF)/VEGF receptor pathways markedly increased the efficacy of treatment with retinal neovascularization (RNV). Regulation of these pathways has a potential for treating RNV, in particular ROP.

Angiogenic Factors Correlate with T Cell Immune Reconstitution and Clinical Outcomes after Double-Unit Umbilical Cord Blood Transplantation in Adults

Umbilical cord blood (UCB) is a valuable graft source for allogeneic hematopoietic stem cell transplantation (HSCT) in patients who lack adult donors. UCB transplantation (UCBT) in adults results in delayed immune reconstitution, leading to high infection-related morbidity and mortality. Angiogenic factors and markers of endothelial dysfunction have biologic and prognostic significance in conventional HSCT, but their role in UCBT has not been investigated. Furthermore, the interplay between angiogenesis and immune reconstitution has not been studied. Here we examined whether angiogenic cytokines, angiopoietin-1 (ANG-1) and vascular endothelial growth factor (VEGF), or markers of endothelial injury, thrombomodulin (TM) and angiopoietin-2 (ANG-2), associate with thymic regeneration as determined by T cell receptor excision circle (TREC) values and recovery of T cell subsets, as well as clinical outcomes in adult recipients of UCBT. We found that plasma levels of ANG-1 significantly correlated with the reconstitution of naive CD4+CD45RA+ and CD8+CD45RA+ T cell subsets, whereas plasma levels of VEGF displayed a positive correlation with CD4+CD45RO+ T cells and regulatory T cells and a weak correlation with TRECs. Assessment of TM and ANG-2 revealed a strong inverse correlation of both factors with naive T cells and TRECs. The angiogenic capacity of each patient's plasma, as determined by an in vitro angiogenesis assay, positively correlated with VEGF levels and with reconstitution of CD4+ T cell subsets. Higher VEGF levels were associated with worse progression-free survival and higher risk of relapse, whereas higher levels of TM were associated with chronic graft-versus-host disease and nonrelapse mortality. Thus, angiogenic factors may serve as valuable markers associated with T cell reconstitution and clinical outcomes after UCBT.

Abnormal phosphorylation of Tie2/Akt/eNOS signaling pathway and decreased number or function of circulating endothelial progenitor cells in prehypertensive premenopausal women with diabetes mellitus

BACKGROUNDS

The number and activity of circulating endothelial progenitor cells (EPCs) in prehypertension is preserved in premenopausal women. However, whether this favorable effect still exists in prehypertensive premenopausal women with diabetes is not clear.

METHODS

This study compared the number and functional activity of circulating EPCs in normotensive or prehypertensive premenopausal women without diabetes mellitus and normotensive or prehypertensive premenopausal women with diabetes mellitus, evaluated the vascular endothelial function in each groups, and investigated the possible underlying mechanism.

RESULTS

We found that compared with normotensive premenopausal women, the number and function of circulating EPCs, as well as endothelial function evaluated by flow-mediated dilatation (FMD) in prehypertensive premenopausal women were preserved. In parallel, the Tie2/Akt/eNOS signaling pathway and the plasma NO level or NO secretion of circulating EPCs in prehypertensive premenopausal women was also retained. However, in presence of normotension or prehypertension with diabetes mellitus, the number or function of circulating EPCs and FMD in premenopausal women decreased. Similarly, the phosphorylation of Tie2/Akt/eNOS signaling pathway and the plasma NO level or NO secretion of circulating EPCs was reduced in prehypertension premenopausal with diabetes mellitus.

CONCLUSION

The present findings firstly demonstrate that the unfavorable effects of diabetes mellitus on number and activity of circulating EPCs in prehypertension premenopausal women, which is at least partially related to the abnormal phosphorylation of Tie2/Akt/eNOS signaling pathway and subsequently reduced nitric oxide bioavailability. The Tie2/Akt/eNOS signaling pathway may be a potential target of vascular protection in prehypertensive premenopausal women with diabetes mellitus.

Angiopoietin-1 improves endothelial progenitor cell-dependent neovascularization in diabetic wounds

BACKGROUND

The diabetic phenotype of wound healing is in part characterized by impaired neovascularization and deficient endothelial progenitor cell (EPC) recruitment. Angiopoietin-1 (Ang-1) is a potent mobilizer of EPCs from the bone marrow (BM). A suggested mechanism for EPC mobilization from the BM is mediated by matrix metalloproteinase 9 (MMP-9) and stem cell factor (SCF). Taken together, we hypothesized that overexpression of Ang-1 in diabetic wounds will recruit EPCs and improve neovascularization and wound healing.

METHODS

An endothelial lineage BM-labeled murine model of diabetes was developed to track BM-derived EPCs. FVBN mice were lethally irradiated and then reconstituted with BM from syngeneic Tie2/LacZ donor mice. Diabetes was induced with streptozotocin. Dorsal wounds in BM-transplanted mice were treated with Ad-Ang-1, Ad-GFP, or phosphate-buffered saline. At day 7 after injury, wounds were harvested and analyzed. A similar experiment was conducted in EPC mobilization deficient MMP-9 -/- mice to determine whether the effects of Ang-1 were EPC-dependent.

RESULTS

Overexpression of Ang-1 resulted in greatly improved re-epithelialization, neovascularization, and EPC recruitment in diabetic BM-transplanted wounds at day 7. Ang-1 treatment resulted in increased serum levels of proMMP-9 and SCF but had no effect on vascular endothelial growth factor levels. According to our FACS results, peripheral blood EPC (CD34(+)/Cd133(+)/Flk1(+)) counts at day 3 after wounding showed impaired EPC mobilization in MMP-9 -/- mice compared with those of wild-type controls. EPC mobilization was rescued by SCF administration, validating this model for EPC-mobilization-deficient mechanistic studies. In MMP-9 -/- mice, Ad-Ang-1 accelerated re-epithelialization in a similar manner, but had no effect on neovascularization.

CONCLUSION

Our results show that Ang-1 administration results in improved neovascularization which is dependent on EPC recruitment and has direct effects on wound re-epithelialization. These data may represent a novel strategy to correct the phenotype of impaired diabetic neovascularization and may improve diabetic wound healing.

Human allogeneic AB0/Rh-identical umbilical cord blood cells in the treatment of juvenile patients with cerebral palsy

BACKGROUND AIMS

The term "cerebral palsy" (CP) encompasses many syndromes that emerge from brain damage at early stages of ontogenesis and manifest as the inability to retain a normal body position or perform controlled movements. Existing methods of CP treatment, including various rehabilitation strategies and surgical and pharmacological interventions, are mostly palliative, and there is no specific therapy focused on restoring injured brain function.

METHODS

During a post-registration clinical investigation, the safety and efficacy of intravenous infusion of allogeneic human leukocyte antigen (HLA)-unmatched umbilical cord blood (UCB) cells were studied in 80 pediatric patients with cerebral palsy and associated neurological complications. Patients received up to 6 intravenous infusions of AB0/Rh-identical, red blood cell-depleted UCB cells at an average dose of 250 × 10(6) viable cells per infusion.

RESULTS

Patients were followed for 3-36 months, and multiple cell infusions did not cause any adverse effects. In contrast, in most patients who received four or more UCB cell infusions, positive dynamics related to significant improvements in neurological status and/or cognitive functions were observed.

CONCLUSIONS

The results confirm that multiple intravenous infusions of allogeneic AB0/Rh-identical UCB cells may be a safe and effective procedure and could be included in treatment and rehabilitation programs for juvenile patients with cerebral palsy.

Umbilical cord blood: a trustworthy source of multipotent stem cells for regenerative medicine

It is conservatively estimated that one in three individuals in the US might benefit from regenerative medicine therapy. However, the relation of embryonic stem cells (ESCs) to human blastocysts always stirs ethical, political, moral, and emotional debate over their use in research. Thus, for the reasonably foreseeable future, the march of regenerative medicine to the clinic will depend upon the development of non-ESC therapies. Current sources of non-ESCs easily available in large numbers can be found in the bone marrow, adipose tissue, and umbilical cord blood (UCB). UCB provides an immune-compatible source of stem cells for regenerative medicine. Owing to inconsistent results, it is certainly an important and clinically relevant question whether UCB will prove to be therapeutically effective. This review will show that UCB contains multiple populations of multipotent stem cells, capable of giving rise to hematopoietic, epithelial, endothelial, and neural tissues both in vitro and in vivo. Here we raise the possibility that due to unique immunological properties of both the stem cell and non-stem cell components of cord blood, it may be possible to utilize allogeneic cells for regenerative applications without needing to influence or compromise the recipient immune system.

Biology and flow cytometry of proangiogenic hematopoietic progenitors cells

During development, hematopoiesis and neovascularization are closely linked to each other via a common bipotent stem cell called the hemangioblast that gives rise to both hematopoietic cells and endothelial cells. In postnatal life, this functional connection between the vasculature and hematopoiesis is maintained by a subset of hematopoietic progenitor cells endowed with the capacity to differentiate into potent proangiogenic cells. These proangiogenic hematopoietic progenitors comprise a specific subset of bone marrow (BM)-derived cells that homes to sites of neovascularization and possess potent paracrine angiogenic activity. There is emerging evidence that this subpopulation of hematopoietic progenitors plays a critical role in vascular health and disease. Their angiogenic activity is distinct from putative "endothelial progenitor cells" that become structural cells of the endothelium by differentiation into endothelial cells. Proangiogenic hematopoietic progenitor cell research requires multidisciplinary expertise in flow cytometry, hematology, and vascular biology. This review provides a comprehensive overview of proangiogenic hematopoietic progenitor cell biology and flow cytometric methods to detect these cells in the peripheral blood circulation and BM.

Bone marrow-derived cells are implicated as a source of lymphatic endothelial progenitors in human breast cancer

Bone marrow-derived endothelial progenitor cells (EPCs) infiltrate into sites of neovascularization in adult tissues and mature into functional blood endothelial cells (BECs) during a process called vasculogenesis. Human marrow-derived EPCs have recently been reported to display a mixed myeloid and lymphatic endothelial cell (LEC) phenotype during inflammation-induced angiogenesis; however, their role in cancer remains poorly understood. We report the in vitro differentiation of human cord blood CD133⁺CD34⁺ progenitors into podoplanin⁺ cells expressing both myeloid markers (CD11b, CD14) and the canonical LEC markers vascular endothelium growth factor receptor 3 (VEGFR-3), lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), and prospero homeobox 1 (PROX-1). These podoplanin⁺ cells displayed sprouting behavior comparable to that of LECs in vitro and a dual hemangiogenic and lymphangiogenic activity in vivo in an endothelial cell sprouting assay and corneal vascularization assay, respectively. Furthermore, these cells expressed vascular endothelium growth factor (VEGF) family members A, -C, and -D. Thus, bone-marrow derived EPCs stimulate hemangiogenesis and lymphangiogenesis through their ability to differentiate into LECs and to produce angiogenic factors. Importantly, plasma from patients with breast cancer induced differentiation of CD34⁺ cord blood progenitors into hemangiogenic and lymphangiogenic CD11b⁺ myeloid cells, whereas plasma from healthy women did not have this effect. Consistent with these findings, circulating CD11b⁺ cells from breast cancer patients, but not from healthy women, displayed a similar dual angiogenic activity. Taken together, our results show that marrow-derived EPCs become hemangiogenic and lymphangiogenic upon exposure to cancer plasma. These newly identified functions of bone-marrow derived EPCs are expected to influence the diagnosis and treatment of breast cancer.

Kallikrein gene-modified EPCs induce angiogenesis in rats with ischemic hindlimb and correlate with integrin αvβ3 expression

Background

Human tissue kallikrein (hTK) plays an essential role in the physiological and pathological mechanisms of blood vessels. This study aimed to determine whether angiogenesis induced by endothelial progenitor cells (EPCs) transduced with the adenovirus-mediated hTK gene could improve blood flow in rat hindlimb ischemia in vivo and to establish a promising mechanism in vitro.

Methods

EPCs transduced with adenovirus encoding hTK-162 (i.e., Ad/hTK-transduced EPCs or Ad/GFP-transduced EPCs) were administered to Wister rats with hindlimb ischemia through therapeutic neovascularization. Muscular capillary density (MCD), blood flow (BF), and the number of myofibers were measured at days 7, 14, and 21 after treatment. Expressions of integrin αvβ3 and endothelial nitric oxide synthase (eNOS) were detected on the surface of EPCs.

Results

MCD, BF, and the number of myofibers in rats with Ad/hTK-transduced EPCs remarkably increased at day 21 after treatment compared with rats with Ad/GFP-transduced EPCs or the control group (P<0.01). Expressions of integrin αvβ3 and eNOS protein on the surface of EPCs also increased in rats with Ad/hTK-transduced EPCs. The levels of integrin αvβ3 expression were reduced by PI3K and eNOS blockade, and the inhibitor of integrin αvβ3 abrogated the migration and adhesion of hTK-transduced EPCs (P<0.05).

Conclusion

hTK gene delivery in vivo improves the natural angiogenic response to ischemia. The ability of hTK gene-transduced EPCs can be enhanced in vitro, in which integrin αvβ3 plays a role in the process.

Transplantation of human cord blood mononuclear cells and umbilical cord-derived mesenchymal stem cells in autism

BACKGROUND

Autism is a pervasive neurodevelopmental disorder. At present there are no defined mechanisms of pathogenesis and therapy is mostly limited to behavioral interventions. Stem cell transplantation may offer a unique treatment strategy for autism due to immune and neural dysregulation observed in this disease. This non-randomized, open-label, single center phase I/II trial investigated the safety and efficacy of combined transplantation of human cord blood mononuclear cells (CBMNCs) and umbilical cord-derived mesenchymal stem cells (UCMSCs) in treating children with autism.

METHODS

37 subjects diagnosed with autism were enrolled into this study and divided into three groups: CBMNC group (14 subjects, received CBMNC transplantation and rehabilitation therapy), Combination group (9 subjects, received both CBMNC and UCMSC transplantation and rehabilitation therapy), and Control group (14 subjects, received only rehabilitation therapy). Transplantations included four stem cell infusions through intravenous and intrathecal injections once a week. Treatment safety was evaluated with laboratory examinations and clinical assessment of adverse effects. The Childhood Autism Rating Scale (CARS), Clinical Global Impression (CGI) scale and Aberrant Behavior Checklist (ABC) were adopted to assess the therapeutic efficacy at baseline (pre-treatment) and following treatment.

RESULTS

There were no significant safety issues related to the treatment and no observed severe adverse effects. Statistically significant differences were shown on CARS, ABC scores and CGI evaluation in the two treatment groups compared to the control at 24 weeks post-treatment (p < 0.05).

CONCLUSIONS

Transplantation of CBMNCs demonstrated efficacy compared to the control group; however, the combination of CBMNCs and UCMSCs showed larger therapeutic effects than the CBMNC transplantation alone. There were no safety issues noted during infusion and the whole monitoring period.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01343511, Title "Safety and Efficacy of Stem Cell Therapy in Patients with Autism".

Ultrasound stimulation restores impaired neovascularization-related capacities of human circulating angiogenic cells

AIMS

Unsatisfactory effects of therapeutic angiogenesis in critical limb ischaemia may be ascribed to use of circulating angiogenic cells (CACs) derived from atherosclerotic patients with impaired neovascularization-related capacities. We tested whether ultrasound cell stimulation can restore the impaired capacities.

METHODS AND RESULTS

During culture of human peripheral blood-derived mononuclear cells for 4 days to achieve CACs, we stimulated the cells in culture daily with low-intensity pulsed ultrasound stimulation (LIPUS). Application of LIPUS to cells in culture derived from healthy volunteers augmented the generation and migration capacities of CACs, increased concentrations of angiopoietin 2 and nitrogen oxides in the culture medium, and increased the expression of phosphorylated-Akt and endothelial nitric oxide synthase in CACs on western blotting. Application of LIPUS to cells in culture derived from atherosclerotic patients also augmented the generation and migration capacities of CACs. Although neovascularization in the ischaemic hindlimb of athymic nude mice was impaired after intramuscular injection of CACs derived from atherosclerotic patients compared with that using CACs derived from healthy volunteers, LIPUS of the cells in culture derived from atherosclerotic patients restored the neovascularization capacities.

CONCLUSION

Therapeutic angiogenesis with LIPUS-pre-treated CACs may be a new strategy to rescue critical limb ischaemia in atherosclerotic patients.

Stem cells in thoracic aortic aneurysms and dissections: potential contributors to aortic repair

BACKGROUND

The hallmark of thoracic aortic aneurysms and dissections (TAAD) is progressive medial degeneration, which can result from excessive tissue destruction and insufficient repair. Although multipotent stem cells (SCs) are important in tissue repair, their role in TAAD is unknown. We sought to determine whether SCs are more abundant in TAAD tissue than in control tissues, and whether SCs within the diseased aortic wall differentiate into functionally relevant cell types.

METHODS

Using immunohistochemistry, we compared the abundance of STRO-1+ cells, c-kit+ cells, and CD34+ cells in aortic tissue from patients with descending thoracic aortic aneurysms (n=12), patients with chronic descending thoracic aortic dissections (n=18), and age-matched organ donors (n=5). Using double immunofluorescence staining, we evaluated SC differentiation into smooth muscle cells, fibroblasts, and macrophages.

RESULTS

All three cell types were significantly more abundant in the media and adventitia of TAAD tissues than in control tissues. We identified subsets of STRO-1+ cells, c-kit+ cells, and CD34+ cells that also expressed the smooth muscle cell marker SM22-α or fibroblast-specific protein-1, suggesting SC differentiation into smooth muscle cells or fibroblasts. Other STRO-1+ cells expressed the macrophage marker CD68, suggesting differentiation into inflammatory cells.

CONCLUSIONS

Stem cells are more abundant in TAAD tissue than in normal aortic tissue. Differentiation of SCs into smooth muscle cells, fibroblasts, and inflammatory cells within the diseased aortic wall suggests that SCs might be involved in both reparative and destructive remodeling processes in TAAD. Understanding the regulation of SC-mediated aortic remodeling will be a critical step toward designing strategies to promote aortic repair and prevent adverse remodeling.

Endothelial progenitor cells and integrins: adhesive needs

In the last decade there have been multiple studies concerning the contribution of endothelial progenitor cells (EPCs) to new vessel formation in different physiological and pathological settings. The process by which EPCs contribute to new vessel formation in adults is termed postnatal vasculogenesis and occurs via four inter-related steps. They must respond to chemoattractant signals and mobilize from the bone marrow to the peripheral blood; home in on sites of new vessel formation; invade and migrate at the same sites; and differentiate into mature endothelial cells (ECs) and/or regulate pre-existing ECs via paracrine or juxtacrine signals. During these four steps, EPCs interact with different physiological compartments, namely bone marrow, peripheral blood, blood vessels and homing tissues. The success of each step depends on the ability of EPCs to interact, adapt and respond to multiple molecular cues. The present review summarizes the interactions between integrins expressed by EPCs and their ligands: extracellular matrix components and cell surface proteins present at sites of postnatal vasculogenesis. The data summarized here indicate that integrins represent a major molecular determinant of EPC function, with different integrin subunits regulating different steps of EPC biology. Specifically, integrin α4β1 is a key regulator of EPC retention and/or mobilization from the bone marrow, while integrins α5β1, α6β1, αvβ3 and αvβ5 are major determinants of EPC homing, invasion, differentiation and paracrine factor production. β2 integrins are the major regulators of EPC transendothelial migration. The relevance of integrins in EPC biology is also demonstrated by many studies that use extracellular matrix-based scaffolds as a clinical tool to improve the vasculogenic functions of EPCs. We propose that targeted and tissue-specific manipulation of EPC integrin-mediated interactions may be crucial to further improve the usage of this cell population as a relevant clinical agent.

Shear stress-induced activation of Tie2-dependent signaling pathway enhances reendothelialization capacity of early endothelial progenitor cells

Although endothelial progenitor cells (EPCs) play a pivotal role in the endothelial repair following arterial injury and shear stress has a beneficial effect on EPCs, however, the molecular mechanism underlying the influence of EPCs on the endothelial integrity and the regulation of shear stress on the EPC signaling remained to be studied. Here, we investigated the effects of laminar shear stress on the tyrosine kinase with immunoglobulin and epidermal growth factor homology domain-2 (Tie2)-dependent signaling and its relation to in vivo reendothelialization capacity of human early EPCs. The human early EPCs were treated with shear stress. Shear stress in a dose-dependent manner increased angiopoietin-2 (Ang2)-induced migratory, adhesive and proliferatory activities of EPCs. Transplantation of EPCs treated by shear stress facilitated in vivo reendothelialization in nude mouse model of carotid artery injury. In parallel, the phosphorylation of Tie2 and Akt of EPCs in response to shear stress was significantly enhanced. With treatment of Tie2 knockdown or Akt inhibition, shear stress-induced phosphorylation of Akt and endothelial nitric oxide synthase (eNOS) of EPCs was markedly suppressed. After Tie2/PI3K/Akt/eNOS signaling was blocked, the effects of shear stress on in vitro function and in vivo reendothelialization capacity of EPCs were significantly inhibited. The present findings demonstrate for the first time that Tie2/PI3k/Akt/eNOS signaling pathway is, at least in part, involved in the EPCs-mediated reendothelialization after arterial injury. The upregulation of shear stress-induced Tie2-dependent signaling contributes to enhanced in vivo reendothelialization capacity of human EPCs.

Fetal progenitor cells naturally transferred through pregnancy participate in inflammation and angiogenesis during wound healing

The phenotype and fate of fetal microchimeric cells transfered into the maternal circulation during pregnancy are not well described. Since progenitors from distal sites mobilize during wound healing, we analyzed the recruitment and plasticity of fetal progenitors into maternal wounds. Wounds were generated on normal and bleomycin-induced fibrotic skin of parous or pregnant wild-type females with fluorescent GFP(+) fetuses. Analyses were performed on skin and blood specimens through PCR, immunohistochemistry, and flow cytometry. Controls consisted of parous and pregnant females without wounds and virgin females with wounds. Fetal cells were detected in all skin specimens of parous mice as long as healing was not achieved. During early stages of wound healing, fetal cells expressed mainly leukocyte markers, while in later phases endothelial markers prevailed. Fetally derived vessels connected to maternal circulation were also found, demonstrating the transfer of fetal endothelial progenitor cells. Wounding mobilized fetal CD34(+)ckit(-) cells into the blood during pregnancy. Most of this population was CD11b(-)VEGFR2(-). Another part was CD11b(+) with a fraction expressing VEGFR2. VEGFa-spiked Matrigel plugs partially mimicked this fetal progenitor recruitment and mobilization into the blood. In summary, fetal cells that mobilize in response to wounding are mainly progenitor cells and participate in angiogenesis and inflammation.

Endothelial progenitor cells: a novel tool for the therapy of ischemic diseases

Circulating endothelial progenitor cells (EPCs) are believed to home to sites of neovascularization, contributing to vascular regeneration either directly via incorporation into newly forming vascular structures or indirectly via the secretion of pro-angiogenic growth factors, thereby enhancing the overall vascular and hemodynamic recovery of ischemic tissues. The therapeutic application of EPCs has been shown to be effective in animal models of ischemia, and we as well as other groups involved in clinical trials have demonstrated that the use of EPCs was safe and feasible for the treatment of critical limb ischemia and cardiovascular diseases. However, many issues in the field of EPC biology, especially in regard to the proper and unambiguous molecular characterization of these cells, still remain unresolved, hampering not only basic research but also the effective therapeutic use and widespread application of these cells. Further, recent evidence suggests that several diseases and pathological conditions are correlated with a reduction in the number and biological activity of EPCs, making the development of novel strategies to overcome the current limitations and shortcomings of this promising but still limited therapeutic tool by refinement and improvement of EPC purification, expansion, and administration techniques, a rather pressing issue.

Guided sprouting from endothelial spheroids in fibrin gels aligned by magnetic fields and cell-induced gel compaction

An aligned engineered microvascular network is critical to the culture of thick or highly metabolic tissue in vitro due to the need for inlet and outlet sides for perfusion of the network. Contact guidance may be a way to achieve aligned networks, but the relationship between the alignment of endothelial sprouts and the alignment of extracellular matrix fibers has yet to be fully elucidated. The data presented here show that sprouts from human blood outgrowth endothelial cell spheroids align with fibrin fibrils, and that the extent to which the sprouts align depends upon the strength of the fibril alignment. This was true for both magnetically-aligned fibrin and fibrin aligned via cell-induced gel compaction, although magnetically-aligned fibrin was more effective over the same culture period. The data also demonstrate that longer sprouts are grown when the fibrils, and thus the sprouts, are more strongly aligned. The formation of aligned endothelial sprouts using these methods can be an essential step in the generation of aligned microvascular networks.

Hyperbaric oxygen: its mechanisms and efficacy

BACKGROUND

This article outlines therapeutic mechanisms of hyperbaric oxygen therapy and reviews data on its efficacy for clinical problems seen by plastic and reconstructive surgeons.

METHODS

The information in this review was obtained from the peer-reviewed medical literature.

RESULTS

Principal mechanisms of hyperbaric oxygen are based on intracellular generation of reactive species of oxygen and nitrogen. Reactive species are recognized to play a central role in cell signal transduction cascades, and the discussion will focus on these pathways. Systematic reviews and randomized clinical trials support clinical use of hyperbaric oxygen for refractory diabetic wound-healing and radiation injuries; treatment of compromised flaps and grafts and ischemia-reperfusion disorders is supported by animal studies and a small number of clinical trials, but further studies are warranted.

CONCLUSIONS

Clinical and mechanistic data support use of hyperbaric oxygen for a variety of disorders. Further work is needed to clarify clinical utility for some disorders and to hone patient selection criteria to improve cost efficacy.

Effect of enhanced external counterpulsation on circulating CD34+ progenitor cell subsets

BACKGROUND

Enhanced external counterpulsation (EECP) is associated with improvement in endothelial function, angina and quality of life in patients with symptomatic coronary artery disease, although the mechanisms underlying the observed clinical benefits are not completely clear. The purpose of this study was to examine the effects of EECP on circulating haematopoietic progenitor cells (HPCs) and endothelial progenitor cells (EPCs) in patients with refractory angina. We compared HPC and EPC counts between patients scheduled for EECP and patients with normal angiographic coronary arteries, with and without coronary endothelial dysfunction. We hypothesized that an increase in circulating bone marrow derived progenitor cells in response to EECP may be part of the mechanism of action of EECP.

METHODS

Thirteen consecutive patients scheduled to receive EECP treatment were prospectively enrolled. Clinical characteristics were recorded and venous blood (5 ml) was drawn on day 1, day 17, day 35 (final session) and one month post completion of EECP therapy. Buffy coat was extracted and HPCs and EPCs were counted by flow cytometry.

RESULTS

Median Canadian Cardiovascular Society (CCS) angina class decreased and Duke Activity Status Index (DASI) functional score increased significantly (both, p < 0.05) in response to EECP, an effect that was maintained at one month after termination of treatment. Flow cytometric analysis revealed an accompanying significant increase in CD34+, CD133+ and CD34+, CD133+ CPC counts over the course of treatment (p < 0.05). DASI scores correlated significantly with CD34+ (R = 0.38 p = 0.02), CD133+ (R = 0.5, p = 0.006) and CD34+, CD133+ (R = 0.47, p = 0.01) CPC counts.

CONCLUSION

This study shows that HPCs, but not EPCs are significantly increased in response to EECP treatment and correlate with reproducible measures of clinical improvement. These findings are the first to link the functional improvement observed with EECP treatment with increased circulating progenitor cells.

Stemming vision loss with stem cells

Dramatic advances in the field of stem cell research have raised the possibility of using these cells to treat a variety of diseases. The eye is an excellent target organ for such cell-based therapeutics due to its ready accessibility, the prevalence of vasculo- and neurodegenerative diseases affecting vision, and the availability of animal models to demonstrate proof of concept. In fact, stem cell therapies have already been applied to the treatment of disease affecting the ocular surface, leading to preservation of vision. Diseases in the back of the eye, such as macular degeneration, diabetic retinopathy, and inherited retinal degenerations, present greater challenges, but rapidly emerging stem cell technologies hold the promise of autologous grafts to stabilize vision loss through cellular replacement or paracrine rescue effects.

Angiopoietins, abdominal aortic aneurysm and atherosclerosis

Abdominal aortic aneurysm (AAA) and atherosclerosis are common causes of mortality and morbidity in an aging population. Angiogenesis is believed to contribute to the development and progression of these diseases. Angiopoietins (angpts) are known to be important regulators of angiogenesis. Angpts can also influence inflammation and have been shown to possess both pro-atherosclerotic and atheroprotective effects. This review explores the potential roles that the angpts play in the development and progression of AAA and atherosclerosis.

Is Endothelium the Origin of Endothelial Progenitor Cells?

Endothelial cells provide the dynamic lining of blood vessels throughout the body and provide many tissue-specific functions, in addition to providing a nonthrombogenic surface for blood cells and conduit for oxygen and nutrient delivery. As might be expected, some endothelial cells are injured or become senescent and are sloughed into the bloodstream, and most circulating endothelial cells display evidence of undergoing apoptosis or necrosis. However, there are rare viable circulating endothelial cells that display properties consistent with those of a progenitor cell for the endothelial lineage. This article reviews historical and current literature to present some evidence that the endothelial lining of blood vessels may serve as a source for rare endothelial colony-forming cells that display clonal proliferative potential, self-renewal, and in vivo vessel forming ability. The article also discusses the current gaps in our knowledge to prove whether the colony-forming cells are in fact derived from vascular endothelium.

Endothelial progenitor cells: identity defined?

In the past decade, researchers have gained important insights on the role of bone marrow (BM)-derived cells in adult neovascularization. A subset of BM-derived cells, called endothelial progenitor cells (EPCs), has been of particular interest, as these cells were suggested to home to sites of neovascularization and neoendothelialization and differentiate into endothelial cells (ECs) in situ, a process referred to as postnatal vasculogenesis. Therefore, EPCs were proposed as a potential regenerative tool for treating human vascular disease and a possible target to restrict vessel growth in tumour pathology. However, conflicting results have been reported in the field, and the identification, characterization, and exact role of EPCs in vascular biology is still a subject of much discussion. The focus of this review is on the controversial issues in the field of EPCs which are related to the lack of a unique EPC marker, identification challenges related to the paucity of EPCs in the circulation, and the important phenotypical and functional overlap between EPCs, haematopoietic cells and mature ECs. We also discuss our recent findings on the origin of endothelial outgrowth cells (EOCs), showing that this in vitro defined EC population does not originate from circulating CD133⁺ cells or CD45⁺ haematopoietic cells.

[Characterization of endothelial progenitor cells and putative strategies to improve their expansion]

Injection of endothelial progenitor cells (EPC) expanded ex vivo has been shown to increase neovascularization in preclinical models of ischemia and in adult patients, but the precise origin and identity of the cell population responsible for these clinical benefits are controversial. Given the potential usefulness of EPC as a cell therapy product, their thorough characterization is of major importance. This review describes the two cell populations currently called EPC and the means to find differential phenotypic markers. We have shown that BMP2/4 are specific markers of late EPC and play a key role in EPC commitment and outgrowth during neovascularization. Several authors have attempted to expand EPC ex vivo in order to obtain a homogeneous cell therapy product. One possible mean of expanding EPC ex vivo is to activate the thrombin receptor PAR-1 with the specific peptide SFLLRN. Indeed, PAR-1 activation increases angiogenic properties of EPC through activation of SDF-1, angiopoietin and IL-8 pathways. This review summarizes the characterization of EPC and different methods of ex vivo expansion.

Angiopoietin-2: development of inhibitors for cancer therapy

Angiopoietin-2 (Ang2) is a member of the Ang family, which plays an important role in angiogenesis during the development and growth of human cancers. Ang2's role in angiogenesis generally is considered as an antagonist for Ang1, inhibiting Ang1-promoted Tie2 signaling, which is critical for blood vessel maturation and stabilization. Ang2 modulates angiogenesis in a cooperative manner with another important angiogenic factor, vascular endothelial growth factor A. Genetic studies have revealed that Ang2 also is critical in lymphangiogenesis during development. However, new evidence suggests more complicated roles for Ang2 in angiogenesis in physiologic processes and invasive phenotypes of cancer cells during progression of human cancers. This article discusses recent studies of Ang2 in angiogenesis and the implication of Ang2 as a therapeutic target as well as a potential inhibitor for antiangiogenesis treatment for cancer patients.

Circulating endothelial progenitor cells

Recent studies have found that bone marrow-derived cells give rise to endothelial cells during states of tissue repair and disease. We have found that one key integrin, integrin-alpha4beta1, promotes the homing of circulating endothelial progenitor cells (EPCs) to sites of ongoing tissue repair. This integrin facilitates the adhesion of EPCs to the vascular endothelium in inflamed tissue or within tumors. We demonstrate how to identify, isolate, purify, and characterize EPCs. We also demonstrate in vivo analysis of the roles of bone marrow-derived cells in tumor growth and angiogenesis by demonstrating adoptive transfer, bone marrow transplantation, tumor models, and immunohistochemistry for markers of blood and endothelial vessels. Finally, we show how to characterize cell adhesion mechanisms regulating bone marrow-derived progenitor cell trafficking.

Inhibition of endothelial progenitor cell differentiation by VEGI

Endothelial progenitor cells (EPCs) play a critical role in postnatal and tumor vasculogenesis. Vascular endothelial growth inhibitor (VEGI; TNFSF15) has been shown to inhibit endothelial cell proliferation by inducing apoptosis. We report here that VEGI inhibits the differentiation of EPCs from mouse bone marrow-derived Sca1(+) mononuclear cells. Analysis of EPC markers indicates a significant decline of the expression of endothelial cell markers, but not stem cell markers, on VEGI-treated cells. Consistently, the VEGI-treated cells exhibit a decreased capability to adhere, migrate, and form capillary-like structures on Matrigel. In addition, VEGI induces apoptosis of differentiated EPCs but not early-stage EPCs. When treated with VEGI, an increase of phospho-Erk and a decrease of phospho-Akt are detected in early-stage EPCs, whereas activation of nuclear factor-kappaB, jun N-terminal kinase, and caspase-3 is seen in differentiated EPCs. Furthermore, VEGI-induced apoptosis of differentiated EPC is, at least partly, mediated by death receptor-3 (DR3), which is detected on differentiated EPC only. VEGI-induced apoptosis signals can be inhibited by neutralizing antibodies against DR3 or recombinant extracellular domain of DR3. These findings indicate that VEGI may participate in the modulation of postnatal vasculogenesis by inhibiting EPC differentiation.

Oxidative stress is fundamental to hyperbaric oxygen therapy

The goal of this review is to outline advances addressing the role that reactive species of oxygen and nitrogen play in therapeutic mechanisms of hyperbaric oxygen. The review will be organized around major categories of problems or processes where controlled clinical trials have demonstrated clinical efficacy for hyperbaric oxygen therapy. Reactive species are now recognized to play a major role in cell signal transduction cascades, and the discussion will focus on how hyperbaric oxygen acts through these pathways to mediate wound healing and ameliorate postischemic and inflammatory injuries.

Circulating CD34+ cell subsets in patients with coronary endothelial dysfunction

BACKGROUND

Endothelial dysfunction is an early manifestation of atherosclerotic disease. Circulating cells that express CD34, including endothelial and hematopoietic progenitor cells, might play a part in the development and progression of atherosclerosis. The aim of this study was to evaluate the association between coronary endothelial dysfunction and concentrations of circulating CD34+ cell subsets.

METHODS

Intracoronary acetylcholine challenge was used to test for coronary endothelial dysfunction in 57 consecutive patients scheduled to undergo diagnostic coronary angiography and with no signs of substantial obstructive lesions. Mononuclear cells were extracted from whole blood samples taken from all patients, analyzed by flow cytometry for CD14, CD34, CD133, CD45, and vascular endothelial growth factor receptor 2 (VEGFR2), and cultured for functional analysis.

RESULTS

Compared with patients with normal coronary endothelial function, in those with coronary endothelial dysfunction, the number of circulating CD34+/CD45(dim)/VEGFR2- cells, CD34+/CD45(dim)/CD133+/VEGFR2- cells and colony-forming units were reduced. Concentrations of CD34+/CD45-/VEGFR2+ cells did not differ between groups.

CONCLUSIONS

Regulation of CD34+ cell subsets seems to differ between patients with coronary endothelial dysfunction and those with normal coronary endothelial function. Changes in specific circulating progenitor cell subsets might, therefore, be an early manifestation of atherosclerosis.

Detailed molecular characterization of cord blood-derived endothelial progenitors

OBJECTIVE

Given their involvement in pathological and physiological angiogenesis, there has been growing interest in understanding and manipulating endothelial progenitor cells (EPC) for therapeutic purposes. However, detailed molecular analysis of EPC before and during endothelial differentiation is lacking and is the subject of the present study.

MATERIALS AND METHODS

We report a detailed microarray gene-expression profile of freshly isolated (day 0) human cord blood (CB)-derived EPC (CD133+KDR+ or CD34+KDR+), and at different time points during in vitro differentiation (early: day 13; late: day 27).

RESULTS

Data obtained reflect an EPC transcriptome enriched in genes related to stem/progenitor cells properties (chromatin remodeling, self-renewal, signaling, cytoskeleton organization and biogenesis, recruitment, and adhesion). Using a complementary DNA microarray enriched in intronic transcribed sequences, we observed, as well, that naturally transcribed intronic noncoding RNAs were specifically expressed at the EPC stage.

CONCLUSION

Taken together, we have defined the global gene-expression profile of CB-derived EPC during the process of endothelial differentiation, which can be used to identify genes involved in different vascular pathologies.

Cord blood stem and progenitor cells

Cord blood has served as a source of hematopoietic stem and progenitor cells for successful repopulation of the blood cell system in patients with malignant and nonmalignant disorders. It was information on these rare immature cells in cord blood that led to the first use of cord blood for transplantation. Further information on these cells and how they can be manipulated both in vitro and in vivo will likely enhance the utility and broadness of applicability of cord blood for treatment of human disease. This chapter reviews information on the clinical and biological properties of hematopoietic stem and progenitor cells, as well as the biology of endothelial progenitor cells, and serves as a source for the methods used to detect and quantitate these important functional cells. Specifically, methods are presented for enumerating human cord blood myeloid progenitor cells, including granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and multipotential (CFU-GEMM or CFU-Mix) progenitors, and their replating potential; hematopoietic stem cells, as assessed in vitro for long-term culture-initiating cells (LTC-ICs), cobblestone area-forming cells (CAFCs), and myeloid-lymphoid-initiating cells (ML-ICs), and as assessed in vivo for nonobese diabetic (NOD)/severe combined immunodeficient (SCID) mouse repopulating cells (SRCs); and high and low proliferative potential endothelial progenitor cells (EPCs).

Identification of two distinct populations of endothelial progenitor cells differing in size and antigen expression from human umbilical cord blood

Endothelial progenitor cells (EPCs) have been isolated from peripheral blood, bone marrow, and umbilical cord blood (CB) and determined to be in heterogeneous populations; however, specific variations in their characteristics remain to be clarified. In this study, we observed that mononuclear cells (MNCs) of CB change in morphology to differentiate into mature endothelial cells (EC) after 6 weeks of culture. In early days of culture along with the differentiation, two distinct populations of EPCs were detected, defined by two-dimensional dot plots (forward scatter vs side scatter) with flow cytometry, namely, relatively small cells (S-EPCs) and relatively large cells (L-EPCs). S-EPCs were found to express CD34 but not CD14, while the converse was the case for L-EPCs. When CD34(+)/CD14(-) cells and CD34(-)/CD14(+) cells were isolated from original MNCs of CB and cultured independently, S-EPCs and L-EPCs were derived from CD34(+)/CD14(-) and from CD34(-)/CD14(+) cells, respectively. Furthermore, when the two EPCs at day 7 were separated by cell sorter and recultured, there was no crossover in terms of CD34 and CD14 expression. While expression of VE-cadherin and vascular endothelial growth factor receptor-2 (VEGFR-2) on L-EPCs was significantly greater than on S-EPCs, levels of CD31 were lower. In addition, L-EPCs exhibited greater proliferative ability on stimulation with VEGF. Although these two EPCs expressed different phenotypes, including growth factor receptors, and had different proliferative ability, they both eventually differentiated into mature ECs after more than 3 weeks of culture.

Changes in circulating human endothelial progenitor cells after brain injury

Endothelial progenitor cells (EPCs) are mobilized from the bone marrow to blood circulation in response to tramatic or inflammatory stimulations. Once released, they actively seek and home to the sites of vascular injury to promote vascular repair. We monitored changes of EPC counts in peripheral blood of 29 patients with traumatic brain injury for up to 21 days. We showed that the levels of circulating EPCs within the first 48 h of injury were lower than control subjects, but increased over time-reaching plateau around 7 days post-injury at a level that was significantly higher than controls. The initial EPC reduction, which was severe in patients with severe injury Glasgow Coma Scale [GCS] < 12), differs from the acute increase in EPC counts found in patients with cardiovascular injury. The subsequent increase in circulating EPCs is primarily through bone marrow mobilization because the cells were stained predominantly for CD133, which labels immature EPCs, but not CD34 (which stains cell of endothelial lineage). The increase appeared earlier in male patients and was greater in those younger than 50 years of age. Changes in circulating EPCs during follow-up periods correlated with platelet, but not leukocyte counts. These results suggest that EPC mobilization following traumatic brain injury may take a different course compared to that associated with body or vascular injuries.

Isolation of progenitor cells from cord blood using adhesion matrices

The aim of this study was to develop optimal conditions for selective adhesion and isolation of mesenchymal progenitor cells (MPCs) from cord blood and to determine their potential for osteogenic differentiation. Mononuclear cells (MNCs) were isolated by Ficoll-Paque gradient and plated onto 48-well culture plates precoated with: human or bovine collagen type I, human collagen type IV, fibronectin or matrigel. Cultures were incubated in alphaMEM containing fetal calf serum. Viability of the adherent cells was determined by alamarBlue(R) assay after 2, 3, and 4 weeks. After 4 weeks in culture, cells were typsinized and replated. Primary cultures were analyzed by histochemistry and third passage cells by FACS. Isolated fibroblast-like cells were cultured in the presence of osteogenic factors and differentiation determined by Alizarin Red S staining, RT-PCR and electron dispersive spectroscopy (EDS). MNCs adhered to all types of matrices with the greatest adhesion rates on fibronectin. These cells were CD45(+), CD105(+), CD14(+), CD49a(+), CD49f(+), CD44(+) and CD34(-). The highest incidence of progenitor cells (PC) was observed on fibronectin and polystyrene. Passages were CD45(-), CD14(-), CD34(-) and weakly CD105(+). Primary cultures expressed endothelial/macrophage RNA markers whether cultured on fibronectin or polystyrene and these markers decreased upon passage. The best osteogenic differentiation was observed in MPCs cultured in osteogenic medium containing vitamin D(3) and FGF9. These cells expressed the bone-related mRNA, collagen type I, core binding factor I (Cbfa I), osteocalcin and osteopontin. EDS of deposits produced by these cells demonstrated a calcium/phosphate ratio parallel to hydroxyapatite. It was concluded that fibronectin increased adhesion rates and isolation potential of cord blood mesenchymal progenitor cells.

Stem cell therapy for autism

Autism spectrum disorders (ASD) are a group of neurodevelopmental conditions whose incidence is reaching epidemic proportions, afflicting approximately 1 in 166 children. Autistic disorder, or autism is the most common form of ASD. Although several neurophysiological alterations have been associated with autism, immune abnormalities and neural hypoperfusion appear to be broadly consistent. These appear to be causative since correlation of altered inflammatory responses, and hypoperfusion with symptology is reported. Mesenchymal stem cells (MSC) are in late phases of clinical development for treatment of graft versus host disease and Crohn's Disease, two conditions of immune dysregulation. Cord blood CD34+ cells are known to be potent angiogenic stimulators, having demonstrated positive effects in not only peripheral ischemia, but also in models of cerebral ischemia. Additionally, anecdotal clinical cases have reported responses in autistic children receiving cord blood CD34+ cells. We propose the combined use of MSC and cord blood CD34+cells may be useful in the treatment of autism.

Endothelial progenitor cells: characterization, in vitro expansion, and prospects for autologous cell therapy

Injection of hematopoietic stem cells or endothelial progenitor cells (EPCs) expanded ex vivo has been shown to augment neovascularization in adult patients, but the precise origin and identity of the cell population responsible for these clinical benefits are controversial. The limited quantity of EPCs in the circulation has been the main obstacle to clinical trials. Several authors have therefore attempted to expand these cells ex vivo in order to obtain a homogeneous cell therapy product. One possible means of expanding EPCs ex vivo is to activate the thrombin receptor PAR-1 with the specific peptide SFLLRN. Indeed, PAR-1 activation promotes cell proliferation and C-X-C chemokine receptor type 4 (CXCR4) dependent migration and differentiation, with an overall angiogenic effect. This review summarizes the results and rationale of clinical trials of angiogenic therapy, the nature of EPCs, the different methods of ex vivo expansion, and current methods of quantification.