Estrogen increases bone marrow-derived endothelial progenitor cell production and diminishes neointima formation

Genous endothelial progenitor cell-capturing stent system: a novel stent technology

Drug-eluting stents have been demonstrated to significantly reduce clinical and angiographic restenosis in patients with coronary artery disease compared with bare-metal stents. Intuitively, however, a prohealing approach for the prevention of in-stent restenosis by promoting accelerated re-endothelialization is favored over the aggressive pharmacologic cytotoxic and cytostatic approach of the drug-eluting stents. The endothelial progenitor cell-capturing stent attracts circulating CD43(+) progenitor cells that bind to the stent surface and differentiate into a functional endothelial layer. It is theorized that the accelerated establishment of the endothelial layer covering the stent struts will reduce the risk of neointimal hyperplasia and smooth muscle cell proliferation. The safety and efficacy have been demonstrated in the nonrandomized Healthy Endothelial Accelerated Lining Inhibits Neointimal Growth (HEALING) studies, and the device received a CE mark in 2005. This article reviews the realization of the endothelial progenitor cell-capturing stent, its relevance compared with other stent types, current evidence on clinical performance, and future perspectives. At present, the larger randomized Tri-stent Adjudication Study (TRIAS) that is ongoing will directly compare the clinical usefulness of this new endothelial progenitor cell-capturing stent with bare-metal stents and drug-eluting stents.

Effects of insulin resistance on endothelial progenitor cells and vascular repair

Insulin resistance, a key feature of obesity, the metabolic syndrome and Type 2 diabetes mellitus, results in an array of metabolic and vascular phenomena which ultimately promote the development of atherosclerosis. Endothelial dysfunction is intricately related to insulin resistance through the parallel stimulatory effects of insulin on glucose disposal in metabolic tissues and NO production in the endothelium. Perturbations characteristic of insulin resistance, including dyslipidaemia, inflammation and oxidative stress, may jeopardize the structural or functional integrity of the endothelium. Recent evidence suggests that endothelial damage is mitigated by endogenous reparative processes which mediate endothelial regeneration. EPCs (endothelial progenitor cells) are circulating cells which have been identified as mediators of endothelial repair. Several of the abnormalities associated with insulin resistance, including reduced NO bioavailability, increased production of ROS (reactive oxygen species) and down-regulation of intracellular signalling pathways, have the potential to disrupt EPC function. Improvement in the number and function of EPCs may contribute to the protective actions of evidence-based therapies to reduce cardiometabolic risk. In the present article, we review the putative effects of insulin resistance on EPCs, discuss the underlying mechanisms and highlight potential therapeutic manoeuvres which could improve vascular repair in individuals with insulin resistance.

Estrogen receptor alpha expression in both endothelium and hematopoietic cells is required for the accelerative effect of estradiol on reendothelialization

OBJECTIVE

E2 accelerates reendothelialization through estrogen receptor alpha (ER alpha), and we now aimed at defining the precise local and systemic cellular actors of this process.

METHODS AND RESULTS

The respective roles of endothelial and hematopoietic targets of E2 were investigated in a mouse carotid injury model, using confocal microscopy, to follow endothelium repair. Grafting ER alpha(-/-) mice with ER alpha(+/+) bone marrow (BM) was not sufficient to restore the accelerative effect of E2 on reendothelialization, demonstrating the necessary role of extrahematopoietic ER alpha. Using an endothelial-specific inactivation of ER alpha (Cre-Lox system), we showed that endothelial ER alpha plays a pivotal role in this E2 action. Conversely, in ER alpha(+/+) grafted with ER alpha(-/-) BM, the E2 regenerative effect was abolished, demonstrating that ER alpha-expressing hematopoietic cells are also needed. As eNOS expression in BM was required for this action, both endothelial progenitor cells and platelets could be the hematopoietic targets that participate to this beneficial E2 effect.

CONCLUSIONS

We demonstrate that endothelial ER alpha plays a pivotal role in E2-mediated reendothelialization. However, endothelial targeting alone is not sufficient because the concomitant stimulation of a subpopulation of BM ER alpha is necessary. This cooperation should be taken into account in strategies aimed at optimizing in-stent reendothelialization.

Endothelial Progenitor Cells and Their Potential Clinical Applications in Peripheral Arterial Disease

Endothelial progenitor cells (EPCs) were originally thought to be present only during embryonic development. New evidence suggests that they can persist into adult life, circulate in the peripheral blood and may play an important part in endothelial repair and replacement of dysfunctional endothelium. They may also play a role in the formation of new blood vessels (angiogenesis, vasculogenesis, and arteriogenesis) in ischemic tissues. In addition, EPCs have the potential to endothelialize small-diameter prosthetic vascular bypass grafts and generate a nonthrombogenic surface, thereby increasing the patency rate of these grafts. EPCs may also be used in the clinical assessment of risk of vascular disease. In this review, the authors discuss the potential use of EPCs in the management of peripheral arterial disease (PAD).

Lovastatin restores the function of endothelial progenitor cells damaged by oxLDL

AIM

The aim of the study was to investigate whether lovastatin restores the survival and function of endothelial progenitor cells (EPCs) damaged by oxLDL.

METHODS

EPCs were preincubated with different concentrations of lovastatin (2, 10, and 50 micromol/L) with or without the Akt inhibitor triciribine for 24 h and were then exposed to 50 microg/mL oxLDL for 48 h. The survival of EPCs, as well as the cellular migration, adhesion, and tube formation of these cells, was examined. To explore the mechanisms of lovastatin's effects on EPCs, the levels of phosphorylated Akt and eNOS and of total eNOS protein and mRNA were assayed.

RESULTS

Incubation of EPCs with oxLDL resulted in significant apoptosis and impaired cellular migration, adhesion and tube structure formation. The detrimental effects of oxLDL on EPC survival and function were attenuated by pretreatment of EPCs with lovastatin. However, when EPCs were pretreated with lovastatin and triciribine at the same time, the beneficial effects of lovastatin were abolished by triciribine. Furthermore, oxLDL caused a significant downregulation of eNOS mRNA and protein expression, as well as a suppression of Akt and eNOS phosphorylation. However, the effects of oxLDL on Akt/eNOS activity and eNOS expression were reversed by lovastatin.

CONCLUSION

Lovastatin reverses the survival and function of EPCs by regulating the Akt/eNOS signaling pathway and the gene transcription of eNOS.

Estradiol-induced, endothelial progenitor cell-mediated neovascularization in male mice with hind-limb ischemia

We investigated whether administration of estradiol to male mice augments mobilization of bone marrow-derived endothelial progenitor cells (EPC) and incorporation into foci of neovascularization after hind-limb ischemia, thereby contributing to blood flow restoration. Mice were randomized and implanted with placebo pellets or pellets containing low-dose estradiol (0.39 mg) or high-dose estradiol (1.7 mg). Hind-limb ischemia was induced by unilateral resection of the left femoral artery 1 week after pellet implantation, then EPC mobilization and functional recovery was evaluated. EPC recruitment was assessed in mice transplanted with bone marrow from transgenic donors expressing beta-galactosidase driven by the Tie-2 promoter. EPC culture assay performed 2 weeks after pellet implantation revealed a significantly greater (p<0.05) number of circulating EPCs in the high-dose estradiol group than in the low-dose estradiol and placebo groups. At 3 and 4 weeks after induction of hind-limb ischemia, perfusion was significantly greater (p<0.05) in high-dose estradiol mice than in mice implanted with the low-dose estradiol or placebo pellets. At 1 and 4 weeks after hind-limb ischemia surgery, more bone marrow-derived EPCs, identified as beta-galactosidase-positive cells, were observed in ischemic regions from high-dose estradiol animals than in low-dose (p<0.05) or placebo groups (p<0.05). These results indicate that estradiol dose-dependently increases the levels of EPCs in peripheral blood in male animals, improves the recovery of blood flow, and decreases limb necrosis after hind-limb ischemia, and that this enhancement occurs, in part, through augmentation of EPC mobilization and greater incorporation of bone marrow-derived EPCs into foci of neovascularization.

Endothelial progenitor cells and their potential clinical implication in cardiovascular disorders

Risk factors associated with cardiovascular diseases reduce the availability of endothelial progenitor cells (EPC) by affecting their mobilization and integration into injured vascular sites. The existence of a bone marrow reservoir of EPC has attracted interest, especially as target for therapeutic intervention in different pathological settings. Among the cardiovascular risk factors, hypertension has been shown to be a strongest predictor of EPC migratory impairment. However, at present, data concerning EPC biology are still limited. In this article we provide an overview of data relevant to their potential clinical implications in cardiovascular disorders. In addition, the recent advances in understanding the role of EPC in the pathophysiology of hypertension are discussed.

Endothelial progenitor cell therapy in atherosclerosis: a double-edged sword?

Atherosclerosis, an inflammatory process that selectively affects arteries, is highly prevalent in human. Thrombo-occlusive complications of atherosclerosis, including stroke and myocardial infarction, are becoming major causes of morbidity and mortality in the industrialized world. Atherosclerosis develops in response to local endothelial injuries. Endothelial dysfunction and cell loss are prominent features in atherosclerosis. Restoring the endothelial lining to normal is critical for slowing or reversing the progression of atherosclerosis. Increasing data suggest that endothelial progenitor cells (EPCs) play a significant role in reendothelialization of the injured blood vessels. This review focuses on the effects of EPC mobilization and transfusion in the condition of atherosclerosis. The aim of the review is to provide an update on the progress in this research field, highlight the role of EPCs in atherosclerosis and discuss the possible mechanisms and potential risks of progenitor cell-based therapy in atherosclerosis.

From bone marrow to the arterial wall: the ongoing tale of endothelial progenitor cells

Several physiological and pathophysiological stimuli or drugs modulate endothelial progenitor cell (EPC) mobilization. Moreover, levels of circulating EPCs predict cardiovascular risk and left ventricular remodelling after myocardial infarction. Nevertheless, our understanding in this field is complicated by lack of an unequivocal definition of EPCs, thus limiting their clinical applications. This review summarizes current knowledge and uncertainties on EPC characterization and mobilization in the attempt to define their role in the management of cardiovascular diseases.

Aging and endothelial progenitor cell telomere length in healthy men

BACKGROUND

Telomere length declines with age in mature endothelial cells and is thought to contribute to endothelial dysfunction and atherogenesis. Bone marrow-derived circulating endothelial progenitor cells (EPCs) are critical to vascular health as they contribute to both reendothelialization and neovascularization. We tested the hypothesis that EPC telomere length decreases with age in healthy adult humans.

METHODS

Peripheral blood samples were collected from 40 healthy, non-obese, sedentary men: 12 young (age 21-34 years), 12 middle-aged (43-55 years) and 16 older (57-68 years). Putative EPCs were isolated from peripheral blood mononuclear cells and telomere length was determined using genomic DNA preparation and Southern hybridization techniques.

RESULTS

EPC telomere length (base pairs) was approximately 20% (p=0.01) lower in the older (8492+523 bp) compared to the middle-aged (10,565+572 bp) and young (10,205+501 bp) men. Of note, there was no difference in EPC telomere length between the middle-aged and young men.

CONCLUSIONS

These results demonstrate that EPC telomere length declines with age in healthy, sedentary men. Interestingly, telomere length was well preserved in the middle-aged compared to young men, suggesting that EPC telomere shortening occurs after the age of 55 years.

Prognostic value of troponin I levels for predicting adverse cardiovascular outcomes in postmenopausal women undergoing cardiac surgery

BACKGROUND

Adverse cardiac events that follow cardiac surgery are an important source of perioperative morbidity and mortality for women. Troponin I provides a sensitive measure of cardiac injury, but the levels after cardiac surgery may vary between sexes. Our purpose in this study was to evaluate the prognostic value of troponin I levels for predicting cardiovascular complications in postmenopausal women undergoing cardiac surgery.

METHODS

The cohort of this study were women enrolled in a previously reported clinical trial evaluating the neuroprotective potential of 17beta-estradiol in elderly women. In that study, 175 postmenopausal women not receiving estrogen replacement therapy and scheduled to undergo coronary artery bypass graft (with or without valve surgery) were prospectively randomized to receive 17beta-estradiol or placebo in a double-blind manner beginning the day before surgery and continuing for 5 days postoperatively. Serial 12-lead electrocardiograms were performed and serum troponin I concentrations were measured before surgery, after surgery on arrival in the intensive care unit, and for the first four postoperative days. The primary end-point of the present study was major adverse cardiovascular events (MACE) defined as a Q-wave myocardial infarction, low cardiac output state or death within 30 days of surgery. The diagnosis of Q-wave myocardial infarction was made independently by two physicians blinded to treatment and patient outcomes with the final diagnosis requiring consensus. Low cardiac output state was defined as cardiac index <2.0 L x min(-1) x m(-2) for >8 h regardless of treatment.

RESULTS

Troponin I levels on postoperative day 1 were predictive of MACE (area under the receiver operator curve = 0.862). A cutoff point for troponin I of >7.6 ng/mL (95% confidence interval, 6.4-10.8) provided the optimal sensitivity and specificity for identifying patients at risk for MACE. The negative predictive value of a troponin I level for identifying a patient with a composite cardiovascular outcome was high (96%) and the positive predictive value moderate (40%). Postoperative troponin I levels were not different between women receiving perioperative 17beta-estradiol treatment compared with placebo and the frequency of MACE was not influenced by 17beta-estradiol treatment.

CONCLUSIONS

In postmenopausal women, elevated troponin I levels on postoperative day 1 are predictive of MACE. Monitoring of perioperative troponin I levels might provide a means for stratifying patients at risk for adverse cardiovascular events.

Ginsenoside Rg1 promotes endothelial progenitor cell migration and proliferation

AIM

To investigate the effect of ginsenoside Rg1 on the migration, adhesion, proliferation, and VEGF expression of endothelial progenitor cells (EPCs).

METHODS

EPCs were isolated from human peripheral blood and incubated with different concentrations of ginsenoside Rg1 (0.1, 0.5, 1.0, and 5.0 micromol/L) and vehicle controls. EPC migration was detected with a modified Boyden chamber assay. EPC adhesion was determined by counting adherent cells on fibronectin-coated culture dishes. EPC proliferation was analyzed with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In vitro vasculogenesis was assayed using an in vitro vasculogenesis detection kit. A VEGF-ELISA kit was used to measure the amount of VEGF protein in the cell culture medium.

RESULTS

Ginsenoside Rg1 promoted EPC adhesion, proliferation, migration and in vitro vasculogenesis in a dose- and time-dependent manner. Cell cycle analysis showed that 5.0 micromol/L of ginsenoside Rg1 significantly increased the EPC proliferative phase (S phase) and decreased the resting phase (G(0)/G(1) phase). Ginsenoside Rg1 increased vascular endothelial growth factor production.

CONCLUSION

The results indicate that ginsenoside Rg1 promotes proliferation, migration, adhesion and in vitro vasculogenesis.

Estrogen-induced gene expression in bone marrow c-kit+ stem cells and stromal cells: identification of specific biological processes involved in the functional organization of the stem cell niche

The recent interest in the role of bone marrow (BM)-derived endothelial progenitor cells (EPCs) and the benefits of estrogen on cardiovascular health brought us to evaluate if estrogen could affect cardiac repair more broadly by regulating biological processes involved in the functional organization of the BM stem cell (SC) niche. To assess such possibility, we evaluated gene expression profiles of BM c-kit+ SCs and CD44+ stromal cells (StroCs) after exposure to a physiological concentration of 17beta-estradiol (17betaE). Data analysis showed that 17betaE altered the expression (>1.5 fold) of 509 and 682 gene probes in c-kit+ SCs and CD44+ StroCs, respectively. Among them, 199 genes in c-kit+ SCs and 283 in CD44+ StroCs were associated to biological process categories of the Gene Ontology classification. Within processes highly regulated by 17betaE, we identified key factors involved in adhesion, migration, proteolysis, and signaling by which 17betaE influences physiological regulation of the functional organization of the SC niche. Together, our results demonstrate that estrogen benefits on cardiovascular health could involve other BM-derived cells than EPCs and that this capacity of estrogen to influence the physiology of the BM SC niche deserves to be investigated clinically.

Endothelial progenitor cells correlate with endothelial function in patients with coronary artery disease

Endothelial progenitor cells (EPC) predict morbidity and mortality in patients at cardiovascular risk.Patients with low EPC counts and impaired endothelial colony forming activity have a higher incidence for cardiovascular events compared to patients with high EPC counts and favorable colony forming activity. The pathophysiological basis for this finding may be an insufficient endothelial cell repair by EPC.We postulate that EPC influence coronary endothelial function which itself is relevant for the outcome of patients at cardiovascular risk. To test this hypothesis in humans, endothelial function was invasively assessed in 90 patients with coronary heart disease by quantitative coronary angiography during intracoronary acetylcholine infusion. Flow cytometry of mononuclear cells isolated from peripheral blood was performed to assess CD133(+) or CD34(+)/KDR(+) EPC. EPC function was assessed ex vivo by determination of endothelial colony forming units. Low EPC number as well as impaired endothelial colony forming activity correlated with severely impaired coronary endothelial function in univariate analysis. Multivariate analysis revealed that only the number of EPC predicts severe endothelial dysfunction independent of classical cardiovascular risk factors. Endothelial function closely correlates with the number of circulating EPC providing new mechanistic insights and options for risk assessment in patients with coronary heart disease.

[Tumor vasculature as a therapeutic target in non-small cell lung cancer]

Despite developments in conventional (chemo)radiotherapy and surgery, survival of non-small cell lung cancer (NSCLC) patients remains poor. Treatments with targeted molecular drugs offer novel therapeutic strategies. Bevacizumab, a recombinant anti-vascular endothelial growth factor (VEGF) antibody, is the antiangiogenic drug at the most advanced stage of development in the therapy of NSCLC. However, a number of questions and future challenges relating to the use of bevacizumab in NSCLC remain. Furthermore, novel agents targeting the pre-existing NSCLC vasculature (i.e. vascular disrupting agents, VDAs) or multiple tyrosine kinase inhibitors have emerged as unique drug classes delivering promising results in several preclinical and clinical studies. Herein, we review the most recent data using these novel targeted agents either alone or in combination with chemotherapy in NSCLC.

Over-expression of hepatocyte growth factor in smooth muscle cells regulates endothelial progenitor cells differentiation, migration and proliferation

BACKGROUND

Endothelial repair is one of key events after vascular injury. The mechanisms by which hepatocyte growth factor (HGF) and endothelial progenitor cells (EPCs) may be responsible for re-endothelialization of injured blood vessel wall are poorly understood.

METHODS

Primary culture SMCs were transfected with pcDNA3.0-HGF followed by G418 selection, one of G418-resistant colonies in well was picked, propagated and used as donor cells for further experiments. HGF and VEGF expression in SMCs were detected with western blot and enzyme linked immunosorbent assays (ELISA). Rat EPCs were cultured in untreated, pcDNA3.0 and pcDNA3.0-HGF transfected SMCs conditioned medium with or without anti-VEGF or exogenous recombinant HGF addition. eNOS, KDR and CD31 expression in EPCs was determined by real-time quantitative polymerase chain reaction (RT-qPCR) or flow cytometry; EPCs migration and proliferation were measured by using a modified Boyden chambers and MTT assay respectively.

RESULTS

Abundant and stable expression of HGF was found in G418-resistant colony-derived SMCs. VEGF expression significantly increased in HGF transfected SMCs. Exogenous recombinant HGF (rHGF) markedly up-regulated eNOS mRNA expression in EPCs and promoted EPCs migration and proliferation, but no significant changes were found in KDR and CD31 mRNA expression. HGF transfection in SMCs was more effective than exogenous HGF for EPCs differentiation, proliferation and migration.

CONCLUSIONS

Over-expression of HGF in SMCs can be helpful for promoting EPCs differentiation, increasing EPCs migration and proliferation. It may be responsible for angiogenesis of arteriosclerosis lesions and useful for blood vessel tissue engineering.

New insights in vascular development: vasculogenesis and endothelial progenitor cells

In the course of new blood vessel formation, two different processes--vasculogenesis and angiogenesis--have to be distinguished. The term vasculogenesis describes the de novo emergence of a vascular network by endothelial progenitors, whereas angiogenesis corresponds to the generation of vessels by sprouting from pre-existing capillaries. Until recently, it was thought that vasculogenesis is restricted to the prenatal period. During the last decade, one of the most fascinating innovations in the field of vascular biology was the discovery of endothelial progenitor cells and vasculogenesis in the adult. This review aims at introducing the concept of adult vasculogenesis and discusses the efforts to identify and characterize adult endothelial progenitors. The different sources of adult endothelial progenitors like haematopoietic stem cells, myeloid cells, multipotent progenitors of the bone marrow, side population cells and tissue-residing pluripotent stem cells are considered. Moreover, a survey of cellular and molecular control mechanisms of vasculogenesis is presented. Recent advances in research on endothelial progenitors exert a strong impact on many different disciplines and provide the knowledge for functional concepts in basic fields like anatomy, histology as well as embryology.

Ambivalence of progenitor cells in vascular repair and plaque stability

PURPOSE OF REVIEW

To discuss crucial cues (chemokines, adhesion molecules and pharmacological means) that guide and control the context-specific mobilization, recruitment and fate of circulating progenitor cells in arterial repair and plaque stability.

RECENT FINDINGS

The mobilization and recruitment of bone marrow derived or resident progenitor cells giving rise to smooth muscle cells have been implicated in accelerated forms of primary plaque formation and neointimal hyperplasia after arterial injury. By contrast, convincing evidence has emerged that the arterial homing of endothelial progenitor cells contributes to endothelial recovery and thereby limits neointimal growth after endothelial denudation. In the chronic context of primary atherosclerosis, plaque progression and destabilization, a more complex picture has become apparent. Clinically, the number and function of endothelial progenitor cells have been linked with an improved endothelial function or regeneration and have been frequently inversely correlated with cardiovascular risk (factors). In animal models, however, the injection of bone marrow cells or endothelial progenitor cells, as well as the application of stem-cell mobilizing factors, have been associated with an exacerbation of atherosclerosis and unstable plaque phenotype, whereas the contribution of smooth muscle progenitors to primary atherosclerosis appears to be more confined to supporting plaque stability.

SUMMARY

Considering the balance between distinct circulating vascular progenitor cells and identifying mechanisms for selective control of their mobilization and homing appears crucial to improve prediction and to directly modulate endogenous vascular remodeling processes.

Sex steroids and stem cell function

Gender dimorphisms exist in the pathogenesis of a variety of cardiovascular, cardiopulmonary, neurodegenerative, and endocrine disorders. Estrogens exert immense influence on myocardial remodeling following ischemic insult, partially through paracrine growth hormone production by bone marrow mesenchymal stem cells (MSCs) and endothelial progenitor cells. Estrogens also facilitate the mobilization of endothelial progenitor cells to the ischemic myocardium and enhance neovascularization at the ischemic border zone. Moreover, estrogens limit pathological myocardial remodeling through the inhibitory effects on the proliferation of the cardiac fibroblasts. Androgens also may stimulate endothelial progenitor cell migration from the bone marrow, yet the larger role of androgens in disease pathogenesis is not well characterized. The beneficial effects of sex steroids include alteration of lipid metabolism in preadipocytes, modulation of bone metabolism and skeletal maturation, and prevention of osteoporosis through their effects on osteogenic precursors. In an example of sex steroid-specific effects, neural stem cells exhibit enhanced proliferation in response to estrogens, whereas androgens mediate inhibitory effects on their proliferation. Although stem cells can offer significant therapeutic benefits in various cardiovascular, neurodegenerative, endocrine disorders, and disorders of bone metabolism, a greater understanding of sex hormones on diverse stem cell populations is required to improve their ultimate clinical efficacy. In this review, we focus on the effects of estrogen and testosterone on various stem and progenitor cell types, and their relevant intracellular mechanisms.

Daily exercise and bone marrow-derived CD34+/133+ cells after myocardial infarction treated by bare metal stent implantation

BACKGROUND

The aims of the present study were to explore the mobilization of bone marrow-derived CD34(+)/133(+) cells in patients with acute myocardial infarction (AMI) and bare metal stent implantation who participated in daily exercise training, and associations with exercise capacity and restenosis.

METHODS AND RESULTS

Participants comprised 23 Japanese men with AMI (Killip 1) who had been treated with a bare metal stent. All patients were advised to walk for 30-60 min/day, at least 4 times per week starting at 11 days after AMI, and were instructed to record the amount of time spent walking each day. At 10 days and then at 3 months after onset of AMI, symptom-limited cardiopulmonary exercise tests were performed and the number of CD34(+)/133(+) cells in the peripheral blood were measured by fluorescence-activated cell sorter analysis. At 3 months after AMI, the number of CD34(+)/133(+) cells and oxygen consumption at anaerobic threshold were higher in the high exercise group (ie, exercise duration >4 h/week) than the low exercise group (ie, exercise duration <2 h/week). At 3 months after AMI, the number of CD34(+)/133(+) cells significantly correlated with oxygen consumption at the anaerobic threshold (p=0.002).

CONCLUSION

Moderate daily exercise of >4 h/week increases exercise capacity and the number of circulating CD34(+)/133(+) cells at 3 months after AMI.

Estrogen-stimulated endothelial repair requires osteopontin

OBJECTIVE

Estradiol (E(2)) is known to accelerate reendothelialization and thus prevent intimal thickening and in-stent restenosis after angioplasty. Transplantation experiments with ERalpha(-/-) mice have previously shown that E(2) acts through local and bone marrow cell compartments to enhance endothelial healing. However, the downstream mechanisms induced by E(2) to mediate endothelial repair are still poorly understood.

METHODS AND RESULTS

We show here that after endovascular carotid artery injury, E(2)-enhanced endothelial repair is lost in osteopontin-deficient mice (OPN(-/-)). Transplantation of OPN(-/-) bone marrow into wild-type lethally irradiated mice, and vice versa, suggested that osteopontin plays a crucial role in both the local and the bone marrow actions of E(2). In the vascular compartment, using transgenic mice expressing doxycyclin regulatable-osteopontin, we show that endothelial cell specific osteopontin overexpression mimics E(2)-enhanced endothelial cell migration and proliferation in the regenerating endothelium. In the bone marrow cell compartment, we demonstrate that E(2) enhances bone marrow-derived mononuclear cell adhesion to regenerating endothelium in vivo, and that this effect is dependent on osteopontin.

CONCLUSIONS

We demonstrate here that E(2) acceleration of the endothelial repair requires osteopontin, both for bone marrow-derived cell recruitment and for endothelial cell migration and proliferation.

Circulating endothelial cells, bone marrow-derived endothelial progenitor cells and proangiogenic hematopoietic cells in cancer: From biology to therapy

Vascularization, a hallmark of tumorigenesis, is classically thought to occur exclusively through angiogenesis (i.e. endothelial sprouting). However, there is a growing body of evidence that endothelial progenitor cells (EPCs) and proangiogenic hematopoietic cells (HCs) are able to support the vascularization of tumors and may therefore play a synergistic role with angiogenesis. An additional cell type being studied in the field of tumor vascularization is the circulating endothelial cell (CEC), whose presence in elevated numbers reflects vascular injury. Levels of EPCs and CECs are reported to correlate with tumor stage and have been evaluated as biomarkers of the efficacy of anticancer/antiangiogenic treatments. Furthermore, because EPCs and subtypes of proangiogenic HCs are actively participating in capillary growth, these cells are attractive potential vehicles for delivering therapeutic molecules. The current paper provides an update on the biology of CECs, EPCs and proangiogenic HCs, and explores the utility of these cell populations for clinical oncology.

Adult progenitor cells in vascular remodeling during atherosclerosis

The mobilization and recruitment of bone marrow-derived, circulating or tissue resident progenitor cells giving rise to smooth muscle-like cells have been implicated in neointima hyperplasia after arterial injury and in accelerated forms of arterial lesion formation, e.g., transplant arteriopathy or graft vasculopathy. By contrast, convincing evidence has emerged that the vascular homing of endothelial progenitor cells (EPCs) contributes to endothelial recovery, thus limiting neointima formation after arterial injury. In the chronic context of primary atherosclerosis, plaque progression and destabilization, a more complex picture has become apparent. In patients with coronary artery disease, the number and function of EPCs have been linked with an improved endothelial function or regeneration, but have been inversely correlated with cardiovascular risk. In animal models, however, the injection of bone marrow cells or EPCs, or the application of stem-cell mobilizing factors, have been associated with an exacerbation of atherosclerosis and unstable plaque phenotypes, whereas the contribution of bone marrow-derived smooth muscle progenitors to primary atherosclerosis appears to be rather confined. Here, we discuss crucial biochemical cues, namely chemokines, adhesion molecules, growth factors and pharmacological means that guide and control the context-specific mobilization, recruitment and fate of vascular progenitor cells in arterial remodeling during atherosclerosis.

Endothelial progenitor cells in neovascularization of infarcted myocardium

Historically, revascularization of ischemic tissue was believed to occur through the migration and proliferation of endothelial cells in nearby tissues; however, evidence accumulated in recent years indicates that a subpopulation of adult, peripheral-blood cells, collectively referred to as endothelial progenitor cells (EPCs), can differentiate into mature endothelial cells. After ischemic insult, EPCs are believed to home to sites of neovascularization, where they contribute to vascular regeneration by forming a structural component of capillaries and by secreting angiogenic factors; new evidence indicates that EPCs can also differentiate into cardiomyocytes and smooth-muscle cells. These insights into the molecular and cellular processes of tissue formation suggest that cardiac function may be preserved after myocardial infarction by transplanting EPCs into ischemic heart tissue, thereby enhancing vascular and myocardial recovery. This therapeutic strategy has been effective in animal models of ischemic disorders, and results from randomized clinical trials suggest that cell-based strategies may be safe and feasible for treatment of myocardial infarction in humans and have provided early evidence of efficacy. However, the scarcity of EPCs in the peripheral blood and evidence that several disease states reduce EPC number and/or function have prompted the development of several strategies to overcome these limitations, such as the administration of genetically modified EPCs that overexpress angiogenic growth factors. To optimize therapeutic outcomes, researchers must continue to refine methods of EPC purification, expansion, and administration, and to develop techniques that overcome the intrinsic scarcity and phenotypic deficiencies of EPCs.

Angiotensin II promotes NO production, inhibits apoptosis and enhances adhesion potential of bone marrow-derived endothelial progenitor cells

Endothelial progenitor cells (EPCs) participate in the processes of postnatal neovascularization and re-endothelialization in response to tissue ischemia and endothelial injury. The level of EPCs present has been found to be directly associated with the outcome of cardiovascular diseases, and could be regulated by stimulatory or inhibitory factors. Given the close relationship between angiotensin II (AngII) and the cardiovascular system, we investigated the effect of AngII on the activities of bone marrow (BM)-derived EPCs. Cells were isolated from BM of rats by density gradient centrifugation. Administration of AngII significantly promoted nitric oxide (NO) release, inhibited EPC apoptosis and enhanced EPC adhesion potential. All of these AngII-mediated effects on EPCs were attenuated by pretreatment with valsartan or L-NAME. Moreover, both LY294002 and wortmannin abolished the anti-apoptotic effect of AngII. Western blot analyses indicated that endothelial NO synthase (eNOS) protein and phosphorylated Akt increased with the treatment of AngII in EPCs. Thus, AngII improved several activities of EPCs through AngII type 1 receptor (AT1R), which may represent a possible mechanism linking AngII and AT1R with angiogenesis. Additionally, AngII-induced NO synthesis through eNOS in EPCs regulates apoptosis and adhesion, and the PI3-kinase/Akt pathway has an essential role in AngII-induced antiapoptosis signaling.

Menstrual cycle influences endothelial progenitor cell regulation: a link to gender differences in vascular protection?

BACKGROUND

The potential role of endothelial progenitor cells (EPCs) in the beneficial effects of estrogen on women's cardiovascular health is of great interest. We thus evaluated if menstrual cycle influences circulating levels of EPC subpopulations in normally menstruating women and if this could underline gender differences.

METHODS AND RESULTS

Ten women and ten men were recruited for this study. Peripheral blood samples were collected at each menstrual cycle phase in women and, three times over a one month period in men. Flow cytometry analysis revealed that, in women, the number of CD133+/CD34-, CD133+/CD34+ progenitor cells (PCs) and CD133+/CD34+/VEGF-R2+ EPCs per ml of blood fluctuated significantly throughout the cycle in synchronization with the level of circulating 17beta-estradiol (17betaE). Maturation of CD133+/VEGF-R2+ and CD133+/CD34-/VEGF-R2+ EPCs towards respective CD144+ advanced EPC (aEPC) subpopulations was reduced at mid-luteal phase. Greater mean global number of CD133+/CD34+ PC, CD133+/VEGF-R2+ and CD133+/CD34-/VEGF-R2+ EPC subpopulations was found in women and 17betaE was identified as a predictive factor for the gender differences perceived. Finally, maturation of CD133+ and CD133+/CD34- towards respective EPCs or aEPCs was increased in women compared to men.

CONCLUSIONS

Our results suggest a physiological regulation of the availability of PC and EPC subpopulations in premenopausal women throughout menstrual cycle and reveal gender differences in the level and maturity of specific PC, EPC and aEPC subpopulations.This cyclic regulation in premenopausal women, may in part explain the lower prevalence of cardiovascular events at middle age compared with men or the timing of such events during the menstrual cycle.

Effects of hormone therapy and dietary soy on myocardial ischemia/reperfusion injury in ovariectomized atherosclerotic monkeys

OBJECTIVE

Hormone therapy (HT) and dietary soy (Soy) inhibit myocardial ischemia/reperfusion (I/R) injury in nonatherosclerotic animals. The aim of this study was to determine their independent and interactive effects on I/R in monkeys previously fed an atherogenic diet for 15 months.

DESIGN

Ovariectomized atherosclerotic monkeys (n = 40) were divided into one of four dietary treatment groups: (1) casein as the protein source, (2) casein and added HT (the equivalent of 5 mug ethinyl estradiol + 1 mg norethindrone acetate daily), (3) Soy protein providing 141 mg total isoflavones daily, or (4) Soy + HT. After 12 months monkeys were anesthetized, and their left anterior descending coronary artery was occluded for 1 hour and reperfused for 4 hours. Infarct size was the percentage of the area at risk not staining with triphenyltetrazolium chloride. Additional measures were myocardial blood flow, stroke volume, coronary output, myeloperoxidase, and malondialdehyde.

RESULTS

There was an interactive negative effect of HT + Soy to increase infarct size from approximately 30% (in other groups) to 55% (P = 0.0004). Additionally, there were negative main effects of Soy on blood flow, coronary output, and stroke volume during I/R (all P values <0.05). There were no effects of treatment on either myeloperoxidase or malondialdehyde.

CONCLUSIONS

Neither HT nor Soy had beneficial effects, whereas their combination had harmful effects, on myocardial I/R injury in monkeys with preexisting atherosclerosis. The mechanism of this negative interaction remains unclear but may relate to Soy's negative effects on hemodynamics.

Aging and disease as modifiers of efficacy of cell therapy

Cell therapy is a promising option for treating ischemic diseases and heart failure. Adult stem and progenitor cells from various sources have experimentally been shown to augment the functional recovery after ischemia, and clinical trials have confirmed that autologous cell therapy using bone marrow-derived or circulating blood-derived progenitor cells is safe and provides beneficial effects. However, aging and risk factors for coronary artery disease affect the functional activity of the endogenous stem/progenitor cell pools, thereby at least partially limiting the therapeutic potential of the applied cells. In addition, age and disease affect the tissue environment, in which the cells are infused or injected. The present review article will summarize current evidence for cell impairment during aging and disease but also discuss novel approaches how to reverse the dysfunction of cells or to refresh the target tissue. Pretreatment of cells or the target tissue by small molecules, polymers, growth factors, or a combination thereof may provide useful approaches for enhancement of cell therapy for cardiovascular diseases.

Vascular actions of estrogens: functional implications

The impact of estrogen exposure in preventing or treating cardiovascular disease is controversial. But it is clear that estrogen has important effects on vascular physiology and pathophysiology, with potential therapeutic implications. Therefore, the goal of this review is to summarize, using an integrated approach, current knowledge of the vascular effects of estrogen, both in humans and in experimental animals. Aspects of estrogen synthesis and receptors, as well as general mechanisms of estrogenic action are reviewed with an emphasis on issues particularly relevant to the vascular system. Recent understanding of the impact of estrogen on mitochondrial function suggests that the longer lifespan of women compared with men may depend in part on the ability of estrogen to decrease production of reactive oxygen species in mitochondria. Mechanisms by which estrogen increases endothelial vasodilator function, promotes angiogenesis, and modulates autonomic function are summarized. Key aspects of the relevant pathophysiology of inflammation, atherosclerosis, stroke, migraine, and thrombosis are reviewed concerning current knowledge of estrogenic effects. A number of emerging concepts are addressed throughout. These include the importance of estrogenic formulation and route of administration and the impact of genetic polymorphisms, either in estrogen receptors or in enzymes responsible for estrogen metabolism, on responsiveness to hormone treatment. The importance of local metabolism of estrogenic precursors and the impact of timing for initiation of treatment and its duration are also considered. Although consensus opinions are emphasized, controversial views are presented to stimulate future research.

Deleterious effects of endogenous and exogenous testosterone on mesenchymal stem cell VEGF production

Modulating the paracrine effects of bone marrow mesenchymal stem cells (BMSCs) may be important for the treatment of ischemic myocardial tissue. In this regard, endogenous estrogen may enhance BMSC vascular endothelial growth factor (VEGF) production. However, little information exists regarding the effect of testosterone on stem cell function. We hypothesized that 1) endogenous or exogenous estrogen will enhance stem cell production of VEGF and 2) endogenous or exogenous testosterone will inhibit BMSC VEGF production. BMSCs were collected from adult male, female, castrated male, and ovariectomized female rats. One hundred thousand cells were incubated with testosterone (1, 10, or 100 nM) or estrogen (0.15, 1.5, or 15 nM) for 48 h. Cell supernatants were collected, and VEGF was measured by ELISA. BMSCs harvested from castrated males, normal females, and ovariectomized females produced more VEGF compared with normal males. Castration was associated with the highest level (1,018 ± 98.26 pg/ml) of VEGF production by BMSCs, which was significantly more than that produced by BMSCs harvested from normal male and normal female animals. Exogenous testosterone significantly reduced VEGF production in BMSCs harvested from ovariectomized females in a dose-dependent manner. Exogenous estrogen did not alter BMSC VEGF production. These findings suggest that testosterone may work on BMSCs to decrease protective growth factor production and that effective removal of testosterone's deleterious effects via castration may prove to be beneficial in terms of protective factor production. By manipulating the mechanisms that BMSCs use to produce growth factors, we may be able to engineer stem cells to produce maximum growth factors during therapeutic use.

Estradiol accelerates endothelial healing through the retrograde commitment of uninjured endothelium

Although the accelerative effect of 17beta-estradiol (E2) on endothelial regrowth has been clearly demonstrated, the local cellular events accounting for this beneficial vascular action are still uncertain. In the present work, we compared the kinetics of endothelial healing of mouse carotid arteries after endovascular and perivascular injury. Both basal reendothelialization as well as the accelerative effect of E2 were similar in the two models. Three days after endothelial denudation, a regenerative area was observed in both models, characterized by similar changes in gene expression after injury, visualized by en face confocal microscopy (EFCM). A precise definition of the injury limits was only possible with the perivascular model, since it causes a complete and lasting decellularization of the media. Using this model, we demonstrated that the migration of uninjured endothelial cells precedes proliferation (bromodeoxyuridine incorporation) and that these events occur at earlier time points with E2 treatment. We have also identified an uninjured retrograde zone as an intimate component of the endothelial regeneration process. Thus, in the perivascular model, the regenerative area can be subdivided into a retrograde zone and a reendothelialized area. Importantly, both areas are significantly enlarged by E2. In conclusion, the combination of the electric perivascular injury model and EFCM is well adapted to the visualization of the endothelial monolayer and to investigate cellular events involved in reendothelialization. This process is accelerated by E2 as a consequence of the retrograde commitment of an uninjured endothelial zone to migrate and proliferate, contributing to an enlargement of the regenerative area.

Circulating bone marrow-derived endothelial progenitor cells: characterization, mobilization, and therapeutic considerations in malignant disease

Until recently, tumor vascularization was thought to occur exclusively through angiogenesis. However, recent studies using different animal models of cancer suggested the importance of bone marrow-derived endothelial progenitor cells (EPCs) (i.e. postnatal vasculogenesis) in tumor vascularization and growth. EPCs are present in the peripheral blood, their levels are increased in response to certain signals/cytokines, and they home into the neovascular bed of malignant tissues. Furthermore, at the clinical level, evidence is emerging that changes in EPC levels might predict the efficacy of anticancer drug combinations that include antiangiogenic agents. On the basis of these observations, EPCs have attractive potential diagnostic and therapeutic applications for malignant diseases. In this paper, we review biological features of EPCs and speculate on the utility of these progenitor cells for medical oncology.

Progenitor cells and vascular disease

Vascular progenitor cells have been the focus of much attention in recent years; both from the point of view of their pathophysiological roles and their potential as therapeutic agents. However, there is as yet no definitive description of either endothelial or vascular smooth muscle progenitor cells. Cells with the ability to differentiate into mature endothelial and vascular smooth muscle reportedly reside within a number of different tissues, including bone marrow, spleen, cardiac muscle, skeletal muscle and adipose tissue. Within these niches, vascular progenitor cells remain quiescent, until mobilized in response to injury or disease. Once mobilized, these progenitor cells enter the circulation and migrate to sites of damage, where they contribute to the remodelling process. It is generally perceived that endothelial progenitors are reparative, acting to restore vascular homeostasis, while smooth muscle progenitors contribute to pathological changes. Indeed, the number of circulating endothelial progenitor cells inversely correlates with exposure to cardiovascular risk factors and numbers of animal models and human studies have demonstrated therapeutic roles for endothelial progenitor cells, which can be enhanced by manipulating them to overexpress vasculo-protective genes. It remains to be determined whether smooth muscle progenitor cells, which are less well studied than their endothelial counterparts, can likewise be manipulated to achieve therapeutic benefit. This review outlines our current understanding of endothelial and smooth muscle progenitor cell biology, their roles in vascular disease and their potential as therapeutic agents.

Reduced number and activity of circulating endothelial progenitor cells in patients with idiopathic pulmonary arterial hypertension

BACKGROUND

Endothelial dysfunction plays a central and critical role in the initiation and development of idiopathic pulmonary arterial hypertension (IPAH), and a variety of evidence suggests that endothelial progenitor cells (EPCs) constitute one aspect of endothelium repair. In addition, transplantation of EPCs could attenuate pulmonary hypertension induced by monocrotaline in rats. However, it has not been examined and reported whether circulating EPCs from patients with IPAH are damaged.

METHODS

EPCs were isolated and cultured from patients with IPAH (n=20) and matched healthy volunteers (n=20). Circulating EPC numbers (enumerated as AC133+KDR+ cells) as well as migratory and adhesive activity were assessed. Blood levels of vascular endothelial growth factor (VEGF), homocysteine (Hcy), B-type natriuretic peptide (BNP), von Willebrand Factor (vWF) and interleukin-6 (IL-6) were also measured.

RESULTS

A significant decrease was observed in circulating EPC (AC133+KDR+ cells, 86.6+/-20.7cells/ml blood vs. 119.6+/-25.4cells/ml blood, P<0.001) numbers and the cell numbers expanded in vitro (47.2+/-14.5 vs. 70.7+/-15.2EPCs/x200 field; P<0.001) in patients with IPAH. EPCs from patients with IPAH were significantly impaired in their migratory capacity and ability to adhere to fibronectin. Blood levels of VEGF, Hcy, BNP, vWF and IL-6 were elevated in patients with IPAH. EPC numbers and activity were inversely related to Hcy, IL-6, BNP and vWF.

CONCLUSIONS

Our observations indicated that EPC numbers and functional capacity were impaired in patients with IPAH, which might not only give potential insight into the pathophysiological mechanisms but also might be useful for identifying suitable therapeutic targets in these patients.

Maternal circulating endothelial progenitor cells in normal singleton and twin pregnancy

OBJECTIVE

The objective of the study was to determine the levels of circulating endothelial progenitor cells (EPCs), which are peripheral blood mononuclear cells (PBMNCs) that contribute to vascular repair in normal pregnancy.

STUDY DESIGN

The concentration of EPCs in maternal blood was measured in healthy nonpregnant women (group A, n = 8), normal singleton pregnancies (group B, n = 24), and normal twin pregnancies (group C, n = 21).

RESULTS

In group A, the mean (SD) level of EPCs was 77.0% (8.6%) adherent PBMNCs. In group B, the mean level was lower than in group A and decreased with gestation from 61.3% (14.9%) in the first trimester to 56.0% (16.2%) in the second trimester and 52.0% (8.7%) in the third trimester (P = .001). Similarly, the level of EPCs in group C was lower than in group A and decreased with gestation from 64.6% (9.6%) in the first trimester to 65.2% (12.7%) in the second trimester and 56.4% (12.6%) in the third trimester (P = .002).

CONCLUSION

Normal pregnancy is associated with a decrease in maternal circulating levels of EPCs.

Rapid endothelial turnover in atherosclerosis-prone areas coincides with stem cell repair in apolipoprotein E-deficient mice

BACKGROUND

Recently, it has been shown that stem/progenitor cells may repair damaged/lost endothelial cells in vein grafts and wire-injured arteries. In the present study, we investigated endothelial cell turnover and regeneration in apolipoprotein E (apoE)(-/-)/transgenic mice carrying LacZ genes driven by an endothelial TIE2 promoter.

METHODS AND RESULTS

To assess cell proliferation on the surface of aortas in apoE(-/-) mice and wild-type controls, BrdU was injected into the tail vein and labeled on en face preparation. BrdU-positive cells on the aortas were observed occasionally in wild-type mice and frequently at sites prone to lesion development in apoE(-/-) mice (0.18+/-0.1% versus 1.12+/-0.2%; P<0.001). Endothelial integrity tests demonstrated that the areas with high rate of cell turnover displayed Evans blue leakage, low levels of VE-cadherin expression, and increased cell attachment, as evidenced by Evans blue dye injection, immunostaining, and scanning electron microscopy, respectively. Furthermore, immunostaining for CD34, Sca-1, Flk-1, and CD133 indicated that approximately 3% to 5% of total cells on the aorta were positive in apoE(-/-) mice. En face double labeling using Ki-67 and progenitor markers revealed that 30% to 50% of progenitor(+) cells expressed Ki-67, indicating a state of proliferation. To clarify the origin of endothelial progenitor cells participating in endothelial repair in apoE(-/-) mice, a chimeric mouse model was created by bone marrow transplantation between apoE(-/-) and LacZ(+/+)/apoE(-/-) mice. Ten months after bone marrow transplantation, approximately 3% to 4% of total cells in the lesion-prone areas were beta-gal positive in apoE(-/-) with apoE(-/-)/TIE2-LacZ bone marrow mice. When cells of aortas from chimeric mice were cultivated on Matrigel-coated plates, a capillary-like structure was found, which showed beta-gal/CD31 or beta-gal/von Willebrand factor double positivity. By a combined analysis of laser dissection microscopy and nest reverse transcription polymerase chain reaction, it was found that beta-gal(+) cells were mainly expressing CD31 and CD144.

CONCLUSIONS

Our findings provide the first quantitative data on endothelial turnover and repair by progenitor cells that are, at least in part, derived from bone marrow during development of atherosclerosis in apoE(-/-) mice.

Stem cells for cardiovascular repair - the challenges of the aging heart

The discovery of extracardiac progenitor cells and resident cardiac stem cells in recent years has led to a great deal of interest in the development of therapeutic strategies that target these endogenous cell sources for promotion of cardiovascular repair mechanisms in the diseased heart. Cardiovascular risk increases with age and among many factors, the age-associated decline in cardiac and vascular regenerative capacity may contribute to the progressive deterioration of cardiovascular health. Thus, understanding the mechanisms which underlie the dysregulation of cardiac stem and progenitor cells may lead to the identification of novel targets and approaches to reverse this decline. In this review, we outline the current knowledge about cardiac stem and progenitor cells, their contribution to cardiovascular regenerative processes and factors that may affect their decreased function in aging individuals. Moreover, we describe the therapeutic strategies that are currently being tested in clinical trials as well as potential new avenues of investigation for the future.

Gender differences in endothelial progenitor cells and cardiovascular risk profile: the role of female estrogens

OBJECTIVE

Endothelial progenitor cells (EPCs) participate in vascular homeostasis and angiogenesis. The aim of the present study was to explore EPC number and function in relation to cardiovascular risk, gender, and reproductive state.

METHODS AND RESULTS

As measured by flow-cytometry in 210 healthy subjects, CD34(+)KDR(+) EPCs were higher in fertile women than in men, but were not different between postmenopausal women and age-matched men. These gender gradients mirrored differences in cardiovascular profile, carotid intima-media thickness, and brachial artery flow-mediated dilation. Moreover, EPCs and soluble c-kit ligand varied in phase with menstrual cycle in ovulatory women, suggesting cyclic bone marrow mobilization. Experimentally, hysterectomy in rats was followed by an increase in circulating EPCs. EPCs cultured from female healthy donors were more clonogenic and adherent than male EPCs. Treatment with 17beta-estradiol stimulated EPC proliferation and adhesion, via estrogen receptors. Finally, we show that the proangiogenic potential of female EPCs was higher than that of male EPCs in vivo.

CONCLUSIONS

EPCs are mobilized cyclically in fertile women, likely to provide a pool of cells for endometrial homeostasis. The resulting higher EPC levels in women than in men reflect the cardiovascular profile and could represent one mechanism of protection in the fertile female population.

The source of neointimal cells in vein grafts: does the origin matter?

The focus of this Commentary is the existing plasticity in the origin of neointimal vascular smooth muscle cells and endothelial cells after vein grafting.

Endothelial progenitor cell therapy for the treatment of coronary disease, acute MI, and pulmonary arterial hypertension: current perspectives

Since their identification in 1997, bone marrow derived endothelial progenitor cells (EPCs) have been studied for their role in the endogenous maintenance and repair of endothelium and their potential regenerative capacity beyond the endothelium. In particular, EPCs have been tested in cell therapy approaches with the aim of developing novel therapies for conditions currently lacking effective treatment options. In this review, we discuss the scientific background and clinical experience using EPC delivery or mobilization for the treatment of post-angioplasty restenosis, acute myocardial infarction and pulmonary arterial hypertension. Although these approaches are safe, efficacy has yet to be proven in large randomized clinical trials. Unfortunately, the biology of EPCs is still poorly understood. The success of future clinical trials depends on a better understanding of EPC biology and intelligent design.

Endothelial progenitor cells, late stent thrombosis and delayed re-endothelialisation

A decade ago, the description of a primitive novel cell type capable of differentiating into cells expressing a mature endothelial cell -phenotype and their capacity to incorporate into regions of active angiogenesis, witnessed the emergence of endothelial progenitor cell (EPC) biology1. The development and maturation of this new concept in vascular biology has resulted in numerous studies describing the role of EPCs in a myriad of disease states where abnormalities of the vasculature have been implicated. Thus, from pre-eclampsia to pulmonary hypertension, erythropoietin administration to erectile dysfunction and cancer to coronary disease the discovery of EPCs has added greatly to the understanding of basic pathophysiology. However, it is in the study of coronary artery -disease where this paradigm shift has had greatest impact, not only regarding basic disease mechanisms, but in the rapid translation of these findings into a clinical context. The purpose of this review is to outline the current understanding of the EPC phenotypes and their relationship with risk factors for coronary disease. In addition, the potential problems of EPC dysfunction and its impact on percutaneous intervention will be appraised together with both pharmacological and stent based strategies to augment EPC -number and function.

Cyclosporin A suppresses proliferation of endothelial progenitor cells: involvement of nitric oxide synthase inhibition

OBJECTIVE

To investigate the effects of the potent immunosuppressive agent cyclosporin A (CsA) on the proliferation of human endothelial progenitor cells (EPCs) and endothelial nitric oxide synthase (eNOS) expression in EPCs.

METHODS AND RESULTS

The EPCs were obtained from cultured mononuclear cells, which were isolated from the peripheral blood of healthy adults, and stimulated with CsA (10 microg/mL) in the presence or absence of either vascular endothelial growth factor (VEGF; 50 ng/mL) or L-arginine (1 mM). To explore the effect of different concentrations of CsA alone on EPC proliferation, some cells were treated with CsA in a series of final concentrations ranging from 0 to 10 microg/mL. Cell proliferation and apoptosis were determined, respectively, by the Cell Counting Kit-8 assay and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. The expression of eNOS was assayed by reverse transcription-polymerase chain reaction analysis while nitric oxide (NO) generation was detected using the Griess method. The effects of CsA on EPC proliferation, apoptosis, and eNOS/NO production were dose dependent in the concentration ranging from 0.1 microg/mL to 10 microg/mL. Treatment with VEGF (50 ng/mL) significantly promoted EPC proliferation and eNOS/NO production, which were completely abrogated by pre-incubation with CsA (10 microg/mL). The supplement of L-arginine (1 mM) promoted NO production that enhanced EPC proliferation and attenuated the effect of CsA on EPC proliferation and apoptosis.

CONCLUSION

CsA significantly inhibited proliferation, eNOS mRNA expression and NO production of human EPCs, in a dose-dependent manner.