Endothelial Progenitor Cells (EPCs) were first identified from human blood samples as a population of circulating mononuclear cells capable of displaying a mature endothelial cell phenotype in culture. Subsequent studies have established that EPCs arise from the bone marrow (BM) and incorporate into the endothelium at sites of blood vessel growth, suggesting a potential role for these cells in neovascularization. Furthermore, a decline in EPC count has been correlated to multiple vascular pathologies, indicating that EPC number could serve as a biomarker of cardiovascular disease. Unfortunately, due to the variability in techniques used for EPC isolation and identification, considerable heterogeneity exists within the population of cells commonly defined as EPCs. In order for the clinical potential of EPCs to be fully realized, thorough characterization of the BM-derived cell populations involved in neovascularization is required. The objective of our study was to determine the functional significance of circulating EPCs in postnatal vascular growth and repair. Two separate strategies were employed to achieve this objective. In the first, we attempted to generate a novel mouse model where the pool of bone marrow-derived endothelial precursors was drastically reduced or eliminated. Our overall approach was to deliver a "suicide" gene, under control of an endothelial cell-specific promoter, to bone marrow cells for use in bone marrow transplantation (BMT) experiments. Mice receiving BMTs would therefore lack the ability to deliver viable BM-derived EPCs to sites of neovascularization. Our central hypothesis for this study was that a reduction in EPC viability would hinder endogenous vascular repair mechanisms, thereby exacerbating cardiovascular disease. In the second strategy, we attempted to identify novel progenitor cell populations based on the transcriptional regulation of pro-angiogenic genes. Our overall approach was to transduce BM with a retrovirus containing a fluorescent reporter gene under control of pro-angiogenic promoters for use in transplantation experiments. Our central hypothesis for this study was that unique populations of BM-derived cells could be identified by expression of the fluorescent reporter gene directed by the Vascular Endothelial Growth Factor (VEGF), endothelial Nitric Oxide Synthase (eNOS) and Vascular Endothelial (VE) Cadherin promoters. The BMT strategy utilized to address our first hypothesis was unsuccessful due to the use of a truncated form of the pro-apoptotic Bax as our suicide gene target. A plasmid encoding GFP fused to the truncated Bax fragment (ΔN-Bax, consisting of amino acids 112-192 of the full length protein) was used in transfection experiments to assess ΔN-Bax function. The GFP:ΔN-Bax fusion protein formed distinct extranuclear aggregates (presumably due to mitochondrial translocation) but did not induce apoptosis in transfected cells. The ΔN-Bax fragment also did not induce cell death when targeted to endothelial cells with retoviral-mediated gene delivery or in a transgenic mouse setting. To address our second hypothesis, we generated retroviral vectors containing the fluorescent tdTomato reporter under control of the VEGF, eNOS and VE Cadherin promoters. Significant fluorescence was detected in cultured endothelial cells and ex vivo-expanded BM cells. Following transplantation of transduced BM cells into lethally irradiated recipient mice, we were able to identify circulating populations of tdTomato-positive cells using flow cytometry. With these results we have identified novel subpopulations of circulating BM-derived cells which may play a significant role in post-natal neovascularization in mice. Therefore, results acquired from these studies could lead to improved cell therapy techniques for treatment of vascular disease.

Endothelial Progenitor Cells (EPCs) are thought to participate in the healing of injured vascular endothelium by incorporating into the defect sites to mediate endothelial recovery. Recently, osteopontin (OPN) was shown to be fundamental in accelerating estrogen-dependent healing of injured blood vessels. Here, we are investigating the effect OPN has on EPC behavior. Late outgrowth human EPCs (LEPCs) were derived from circulating monocytes isolated by leukophoresis, and grown in culture until passage six. L-EPCs were then assayed for adhesion, spreading, chemotaxis, and haptotaxis, as well as resistance to detachment by flow electric cellsubstrate impedance sensing (ECIS). The results of standard and ECIS methods showed both dose and time dependent responses in cell adhesion and spreading. In addition, OPN promoted haptotactic migration of EPCs in Boyden chamber assays. LEPCs seeded onto 10μM OPN substrates and exposed to laminar flow had grater survival and higher resistance to detachment than OPN/static and flow only conditions. CD44 and !1 integrins were only responsible for approximately 50% of LEPCs adhesion to OPN compared to the unblocked condition. Western blots showed that Rho GTPases were activated in L-EPCs seeded on OPN. However, this activation could not be completely blocked by either CD44 or !1 integrin antagonists. These data confirm the direct effects of OPN on EPCs adhesion, and suggest that OPN works by mediating cell adhesion during vascular injury.

Fetal growth in utero depends on nutrient and oxygen reaching the fetus through the uterine and placental microcirculations, both undergoing massive expansion during pregnancy. Aberrations of the placental vasculature are associated with Intrauterine Growth Restriction (IUGR), a common pathological outcome of pregnancy; however, the cellular components responsible for vessel formation in the placenta and the uterus remain unknown. Endothelial Progenitor Cells (EPC) are a group of morphologically and functionally varied bone marrow derived vasculogenic cell types, divided into two major subsets: (i) Circulating Angiogenic Cells (CACs), which promote vessel formation by interfering with the extracellular matrix and (ii) Endothelial Colony Forming Cells (ECFCs), which provide the source for new endothelium. This role has been demonstrated in pathophysiological studies, but not in normal physiological events in vivo. Fetal ECFCs are more proficient than their adult counterparts, but it is unclear in what specific fetal or maternal physiological situations fetal ECFCs are involved. Based upon these considerations, it was hypothesised that: (i) fetal-derived ECFCs play a role in placental vasculogenesis, (ii) these cells transmigrate the placenta and home to loci of vessel formation in the pregnant uterus, and that (iii) intrinsic alterations in their capabilities are associated with fetal growth restriction during intrauterine life. To support these hypotheses the following experiments were performed;(i) EPCs in blood from pairs of human umbilical arteries and veins were counted by flow cytometry. Numbers of EPCs in these samples showed an arterio-venous gradient suggesting their placental sequestration. Furthermore, ECFCs were isolated from human umbilical blood using established culture techniques. Labelled human fetal ECFCs were transplanted into the circulation of murine fetuses using an ultrasound-guided intra-cardiac injection. Using a fluorescent imager and microscopy these cells were shown to home to the murine placenta and participate in vasculogenesis.(ii) Male mice ubiquitously expressing eGFP were crossbred with native females, and fetal (eGFP-positive) endothelial-like cells integrated into the uterine microvasculature. Human fetal ECFCs injected into murine fetuses were shown to migrate to the maternal uterus and became functionally involved with the microvasculature. In humans, microvessels were isolated from uterine biopsies of mothers with male offspring. Copies of the male specific SRY gene (quantified by RT-QPCR) indicated that cells of fetal origin constituted 12% of the endothelium in these vessels. In cross-sections, hybridisation of the Y-chromosome demonstrated the presence of fetal cells in the maternal endothelium of the human uterus. (iii) Using flow cytometry, fewer EPCs were defined within the peripheral circulation of growth-restricted babies. Functional assays showed that ECFCs derived from these growth-restricted cases had intrinsically impaired proliferation, migration, matrix-metalloproteinase (MMP-2) production, and generated fewer blood vessels in a murine vasculogenic bioassay. These results demonstrated the vasculogenic capacity of human fetal ECFCs in vivo and established them as key players in human placental vasculogenesis and uterine vessel expansion. Notably, these results also showed a link between impaired function of fetal ECFCs and IUGR, which is associated with increased cardiovascular risk of both the fetus as an adult, and mother in later life. From these findings it could be speculated, that intrinsic changes in ECFC-biology may be the causative link between IUGR and fetal and maternal cardiovascular susceptibility. Insight into these processes may contribute to early diagnosis, prevention and treatment of IUGR and associated conditions.

Ageing poses one of the largest risk factors for the development of cardiovascular disease (CVD). The increased propensity towards vascular pathology with advancing age maybe explained, in part, by a reduction in the ability of circulating endothelial progenitor cells (EPCs) to contribute to vascular repair and regeneration. Among all current putative EPC populations, outgrowth endothelial cells (OECs) display the most features consistent with a human postnatal vasculogenic cell. Cell-surface heparan sulfate (HS) proteoglycans, by virtue of specific sulfated domains within the glycosaminoglycan chain, are able to bind and modulate the activities of a variety of proteins important for EPC mobilisation, homing and function at sites requiring neovascularization. This study aimed to determine if human OEC function is impaired with age, and to ascertain whether this is accompanied by changes in the fine structure of OEC HS.Using in vitro cell culture methods, OECs were isolated from healthy subjects across an age range and cell phenotype was verified by the demonstration of numerous endothelial, but not hematopoietic, cell characteristics. The functional capacity of peripheral blood derived OECs from young and old subjects, and comparative cord blood derived OECs, was assessed in terms of their susceptibility to apoptosis, proliferative, migratory and tube-forming capabilities. In vitro scratch and transwell migration assays revealed that the migratory capacity of peripheral blood derived OECs isolated from old subjects was impaired in comparison to those from young subjects and cord blood derived OECs. Structural analysis of HS by high performance liquid chromatography (HPLC) demonstrated a significant reduction in the relative percentage of the trisulfated disaccharide, 2-O-sulfated-uronic acid, N, 6-O-sulfated-glucosamine (UA[2S]-GlcNS[6S]), within OEC HS with age (r = -0.847, p=<0.01). Moreover, a decline in the migratory response of OECs towards a gradient of VEGF significantly correlated with the percentage expression of this disaccharide (r = 0.840, p<0.01). Disruption of cell surface HS by pre-treatment with heparinase I and III was found to significantly reduce the VEGF-induced migratory response of peripheral blood derived OECs isolated from young subjects to levels similar to that observed for OECs from older individuals. Understanding the role of HS in regulating the directional migration of EPCs to sites requiring neovascularization and developing approaches to facilitate EPC migration may aid in the design of more successful strategies to optimise the regenerative capacity of these cells in the ageing vasculature.

Endothelial Progenitor Cells (EPCs) are thought to participate in the healing of injured vascular endothelium by incorporating into the defect sites to mediate endothelial recovery. Recently, osteopontin (OPN) was shown to be fundamental in accelerating estrogen-dependent healing of injured blood vessels. Here, we are investigating the effect OPN has on EPC behavior. Late outgrowth human EPCs (LEPCs) were derived from circulating monocytes isolated by leukophoresis, and grown in culture until passage six. L-EPCs were then assayed for adhesion, spreading, chemotaxis, and haptotaxis, as well as resistance to detachment by flow electric cellsubstrate impedance sensing (ECIS). The results of standard and ECIS methods showed both dose and time dependent responses in cell adhesion and spreading. In addition, OPN promoted haptotactic migration of EPCs in Boyden chamber assays. LEPCs seeded onto 10μM OPN substrates and exposed to laminar flow had grater survival and higher resistance to detachment than OPN/static and flow only conditions. CD44 and !1 integrins were only responsible for approximately 50% of LEPCs adhesion to OPN compared to the unblocked condition. Western blots showed that Rho GTPases were activated in L-EPCs seeded on OPN. However, this activation could not be completely blocked by either CD44 or !1 integrin antagonists. These data confirm the direct effects of OPN on EPCs adhesion, and suggest that OPN works by mediating cell adhesion during vascular injury.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19620号 / 医博第4127号 / 新制||医||1015(附属図書館) / 32656 / 京都大学大学院医学研究科医学専攻 / (主査)教授 武藤 学, 教授 森田 智視, 教授 山下 潤 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Endometriosis affects 5-10% of women and is characterized by the growth of endometrial tissue outside of the uterus. Treatment for endometriosis primarily focuses on symptom relief, is short term with severe side effects and often leads to recurrence of the condition. Establishing new blood supply is a fundamental requirement for endometriosis lesions growth. This has led to the idea that antiangiogenic therapy may be a successful approach for inhibiting endometriosis. Recent evidence indicates that endothelial progenitor cells (EPCs) contribute to neoangiogenesis of endometriotic lesions. These EPCs are recruited to the lesion site by stromal cell-derived factor-1 (SDF-1). We hypothesize that SDF-1 is central to the neoangiogenesis and survival of endometriotic lesions and that administration of SDF-1 blocking antibody will inhibit lesion growth by inhibiting angiogenesis in a murine model of endometriosis. Immunohistochemistry for SDF-1 and CD34 was performed on human endometriosis and normal endometrial samples. Quantification of SDF-1 and EPCs was performed in the blood of endometriosis patients and controls using ELISA and flow cytometry, respectively. A new mouse model of endometriosis was developed using BALB/c-Rag2-/-/IL2rg-/- mice to investigate role of SDF-1 in neoangiogenesis. Either SDF-1 blocking antibody or an isotype control was administered on a weekly basis for four weeks. Weekly samples of peripheral blood from mice were analyzed for SDF-1, other cytokines of interest and EPCs. Mice were euthanized at seven weeks to observe lesion growth and blood vessel development. Our results indicate overabundance of SDF-1 and CD34+ progenitor cells in human endometriotic lesions compared to eutopic endometrium. In the mouse model, SDF-1 and circulating EPC levels decreased from pre-treatment levels after one week, and remained constant over the course of the treatment in both SDF-1 blocking antibody and isotype control groups. In the SDF-1 blocking group, reduced vascularity of lesions, identified by immunofluorescence staining for CD31, was revealed compared to isotype controls. These findings suggest that SDF-1 may be responsible for CD34+ progenitor cell recruitment to the neoangiogenic sites in endometriosis. Blocking of SDF-1 reduces neovascularization of human endometriotic lesions in a mouse model. Further studies on blocking SDF-1 in combination with other antiangiogenic agents are needed. / Thesis (Master, Anatomy & Cell Biology) -- Queen's University, 2011-12-21 19:34:43.054

No description available.

<p>Endothelial dysfunction is the predominant pathophysiological state prior to the onset of atherosclerosis. Currently, treatments for endothelial dysfunction are evaluated in vitro using two-dimensional (2D) cell culture assays or in vivo animal models. Microphysiological systems are small-scale three-dimensional (3D) tissue models that recapitulate the native tissue structure and function. An ideal microphysiological system is comprised of human cells embedded within a 3D matrix introduced to physiological fluid perfusion. Immune challenge in the form of cytokines or immune cells further recapitulates the native microenvironment.</p><p>A vascular microphysiological system was developed from a small-diameter tissue engineered blood vessel (TEBV) in a perfusion culture circuit. TEBVs were created from collagen gels embedded with human neonatal dermal fibroblasts and plastically compressed to yield collagen constructs with high fiber densities. TEBVs are rapidly producible and can be directly introduced into perfusion culture immediately after fabrication. Endothelium-independent vasoconstriction in response to phenylephrine and endothelium-dependent vasodilation in response to acetylcholine were used to analyze the health and function of the endothelium non-destructively over time.</p><p>Endothelial dysfunction was induced through introduction of the pro-inflammatory cytokine tumor necrosis factor – α (TNF-α). Late-outgrowth endothelial progenitor cells derived from the peripheral blood of coronary artery disease patients (CAD EPCs) were evaluated as a potential endothelial source for autologous implantation in both a two-dimensional (2D) direct co-culture model as well as a 3D model as an endothelial source for a tissue engineered blood vessel. CAD EPCs demonstrated similar adhesive properties to a confluent, quiescent layer of smooth muscle compared to human aortic endothelial cells. Within the TEBV system, CAD EPCs demonstrated the capacity to elicit endothelium-dependent vasodilation. CAD EPCs were compared to adult EPCs from young, healthy volunteers. Both CAD EPCs and healthy volunteer EPCs demonstrated similar endothelium-dependent vasoactivity in response to acetylcholine; however, in response to TNF-α, CAD EPCs demonstrated a reduced response to phenylephrine at high doses.</p><p>The treatment of TEBVs with statins was explored to model the drug response within the system. TEBVs were treated with lovastatin, atorvastatin, and rosuvastatin for three days prior to exposure to TNF-α. In all three cases, statins prevented TNF-α induced vasoconstriction in response to acetylcholine within the TEBVs, compared to TEBVs not treated with statins. Overall, this work characterizes and validates a novel vascular microphysiological system that can be tested in situ in order to determine the effects of various patient populations and drugs on endothelial health and function under healthy and inflammatory conditions.</p> / Dissertation

Les maladies thrombotiques sont la cause majeure de décès dans les pays industrialisés. Les cellules souches dérivées de la moelle osseuse ont été impliqués dans la réparation vasculaire et contribuent à restaurer l'intégrité de l'endothélium. Les cellules progéniteurs CD34 positives ont été rapportées pour jouer un rôle important suite à une blessure de la paroi vasculaire en se liant aux plaquettes ou à la fibrine, modulant la formation du thrombus et participant à la ré-endothélialisation de la paroi vasculaire lésée. Parmi les cellules progéniteurs CD34 positives, les cellules endothéliales formant colonie (ECFC) ont été caractérisés comme présentant des propriétés endothéliale. La première partie de ce travail met en évidence un nouveau partenariat entre les neutrophiles et les ECFC. Par l'utilisation de la microscopie intravitale chez les souris, nous montrons que les neutrophiles recrutent les ECFC au site de lésion vasculaire induite par rayon laser. Ce recrutement est dépendant du PSGL-1 mais indépendant de l'expression de la P-sélectine. L'interaction avec les neutrophiles accroît le potentiel pro-angiogénique des ECFC in vitro. L'identification de ce nouveau partenariat entre les neutrophiles et les ECFC dans la formation de thrombus possède des implications potentiellement critiques dans le contrôle de l'angiogenèse.&#8232;La seconde partie de ce travail décrit une nouvelle méthode pour imager en temps réel le devenir des ECFCs in vivo. Nos résultats montrent que les ECFC s'accumule au site de lésion vasculaire.&#8232;En conclusion, ce travail démontre que les ECFC peuvent participer favoriser et réguler l'angiogenèse en interagissant avec les neutrophiles. / Thrombotic diseases are major cause of death in industrialized countries. Bone marrow derived progenitor cells have been implicated in vascular repair and contribute to restore the integrity of endothelium, thus constituting important partners for vascular wall restoration. CD34 positive progenitors cells were reported to play an important role following an injury of the vessel wall by binding to platelets or fibrin, modulating thrombus formation and participating in the re-endothelization of the injured vessel wall. Among CD34 positive progenitors cells, Endothelial Colony forming Cells (ECFCs) have been characterized as a unique subset displaying endothelial properties. The first part of this work described a new partnership between neutrophils and ECFCs. Using high- speed digital fluorescent intravital microscopy in living mice we show that neutrophils recruit ECFCs at the site of a laser-induced vessel injury via PSGL-1 axis independently of P-selectin. This interaction enhances the pro-angiogenic potential of ECFCs in vitro. The identification a new central partnership between neutrophils and ECFC in thrombus formation has critical potential implications to control angiogenesis.&#8232;The second part of this work, described a new method to image in real-time the homing and survival ECFCs in vivo. Our results show that ECFCs transducted with a gene coding for luciferase accumulates at site of vascular traumatism.&#8232;In conclusion, this work indicates that ECFCs may participate in the promotion and regulation of angiogenesis by interacting with neutrophils at a site of vascular traumatism.