Estrogen induces endothelial progenitor cells proliferation and migration by estrogen receptors and PI3K-dependent pathways

Distinct roles of estrone and estradiol in endothelial colony-forming cells

Our current understanding of the relationship between estrogen and human endothelial colony-forming cell (hECFC) function is based almost exclusively on studies investigating estradiol action at nuclear estrogen receptors. In the current study the hypothesis was tested that the less potent estrogen receptor agonist, estrone, affects hECFC proliferation, migration, secretion, and tube formation in a way that is unique from that of estradiol. The relationship between the estrogens, estradiol and estrone, is clinically important, particularly in postmenopausal women where estradiol levels wane and estrone becomes the predominant estrogen. Cultured hECFCs from peripheral blood mononuclear cell fractions were treated with concentrations of estradiol and estrone ranging from 1 nM to 1 μM separately and in combination. Following treatment, proliferation, migration, ability to attract other hECFCs (autocrine secretion), and ability to enhance endothelial cell tube formation (tubulogenesis) were tested. Functional assays revealed unique, concentration-dependent physiological effects of estrone and estradiol. Estradiol exposure resulted in increased hECFC proliferation, migration, secretion of chemoattractant, and enhancement of tube formation as expected. As with estradiol, hECFC secretion of chemoattractant increased significantly with each increase in estrone exposure. Estrone treatment produced a biphasic, concentration-dependent relationship with proliferation and tube formation and relatively no effect on hECFC migration at any concentration. The quantitative relationship between the effects of estrone and estradiol and each hECFC function was analyzed. The extent to which estrone was similar in effect to that of estradiol was dependent on both the concentrations of estradiol and estrone and the hECFC function measured. Interestingly, when the two estrogens were present, differing ratios resulted in unique functional responses. hECFCs that were treated with combinations of estrone and estradiol with high estrone to estradiol ratios showed decreased proliferative capacity. Conversely, hECFCs that were treated with combinations that were relatively high in estradiol, showed increased proliferative capacity. Cells that were treated with estrone and estradiol in equal concentrations showed an attenuated proliferative response that was decreased compared to the proliferation that either estrone or estradiol produced when they were present alone. This co-inhibitory relationship, which has not been previously reported, challenges the prevailing understanding of estrone as solely a weak agonist at estrogen receptors. This study provides evidence that estrone signaling is distinct from that of estradiol and that further investigation of estrone's mechanism of action and the biological effect may provide important insight into understanding the dysfunction and decreased number of hECFCs, and the resulting cardiovascular disease risk observed clinically in menopausal women and women undergoing hormone replacement therapy.

The role of phosphoinositide 3-kinases in immune-inflammatory responses: potential therapeutic targets for abdominal aortic aneurysm

The pathogenesis of abdominal aortic aneurysm (AAA) includes inflammatory responses, matrix metalloproteinases (MMPs) degradation, VSMC apoptosis, oxidative stress, and angiogenesis, among which the inflammatory response plays a key role. At present, surgery is the only curing treatment, and no effective drug can delay AAA progression in clinical practice. Therefore, searching for a signaling pathway related to the immune-inflammatory response is an essential direction for developing drugs targeting AAA. Recent studies have confirmed that the PI3K family plays an important role in many inflammatory diseases and is involved in regulating various cellular functions, especially in the immune-inflammatory response. This review focuses on the role of each isoform of PI3K in each stage of AAA immune-inflammatory response, making available explorations for a deeper understanding of the mechanism of inflammation and immune response during the formation and development of AAA.

Sex Differences in Renal Function: Participation of Gonadal Hormones and Prolactin

Kidney pathophysiology is influenced by gender. Evidence suggests that kidney damage is more severe in males than in females and that sexual hormones contribute to this. Elevated prolactin concentration is common in renal impairment patients and is associated with an unfavorable prognosis. However, PRL is involved in the osmoregulatory process and promotes endothelial proliferation, dilatation, and permeability in blood vessels. Several proteinases cleavage its structure, forming vasoinhibins. These fragments have antagonistic PRL effects on endothelium and might be associated with renal endothelial dysfunction, but its role in the kidneys has not been enough investigated. Therefore, the purpose of this review is to describe the influence of sexual dimorphism and gonadal hormones on kidney damage, emphasizing the role of the hormone prolactin and its cleavage products, the vasoinhibins.

Tumors modulate fenestrated vascular beds and host endocrine status

Allograft and xenograft transplantation into a mouse host is frequently utilized to study cancer biology, tumor behavior, and response to treatment. Preclinical studies employing these models often focus solely upon the intra-tumoral effects of a given treatment, without consideration of systemic toxicity or tumor-host interaction, nor whether this latter relationship could modulate the toxicologic response to therapy. Here it is demonstrated that the implantation and growth of a range of human- and mouse-derived cell lines leads to structural vascular and, potentially, functional changes within peripheral endocrine tissues, a process that could conceivably ameliorate the severity of anti-angiogenic-induced fenestrated vessel attenuation. Observations suggest a multifactorial process, which may involve host- and tumor-derived cytokines/growth factors, and the liberation of myeloid-derived suppressor cells. Further investigation revealed a structurally comparable response to the administration of exogenous estrogen. These findings, in addition to providing insight into the development of clinical anti-angiogenic "adaptation," may be of significance within the "cancer-cachexia" and cancer-related anemia syndromes in man.

Immune Cell Therapies to Improve Regeneration and Revascularization of Non-Healing Wounds

With the increased prevalence of chronic diseases, non-healing wounds place a significant burden on the health system and the quality of life of affected patients. Non-healing wounds are full-thickness skin lesions that persist for months or years. While several factors contribute to their pathogenesis, all non-healing wounds consistently demonstrate inadequate vascularization, resulting in the poor supply of oxygen, nutrients, and growth factors at the level of the lesion. Most existing therapies rely on the use of dermal substitutes, which help the re-epithelialization of the lesion by mimicking a pro-regenerative extracellular matrix. However, in most patients, this approach is not efficient, as non-healing wounds principally affect individuals afflicted with vascular disorders, such as peripheral artery disease and/or diabetes. Over the last 25 years, innovative therapies have been proposed with the aim of fostering the regenerative potential of multiple immune cell types. This can be achieved by promoting cell mobilization into the circulation, their recruitment to the wound site, modulation of their local activity, or their direct injection into the wound. In this review, we summarize preclinical and clinical studies that have explored the potential of various populations of immune cells to promote skin regeneration in non-healing wounds and critically discuss the current limitations that prevent the adoption of these therapies in the clinics.

17β-Estradiol Accelerated Renal Tubule Regeneration in Male Rats After Ischemia/Reperfusion-Induced Acute Kidney Injury

Ischemic/reperfusion injury (IRI) is the most common cause of acute kidney injury (AKI). Murine studies report that pretreatment with 17β-estradiol protects against AKI using multiple mechanisms, but how 17β-estradiol is involved in regenerating tubular cells is unknown. To visualize the kidney injury and repair, we used 17β-estradiol to treat rats with postischemic acute kidney injury. AKI was induced by clamping the renal pedicle for 90 minutes 2 weeks after a unilateral nephrectomy. Rats were treated with an intravenous injection of 17β-estradiol or vehicle immediately after reperfusion. Kidney injury was assessed by measuring biochemical and histopathological changes. Immunohistochemical staining of vimentin, proliferating cell nuclear antigen (PCNA), and E-cadherin were used to assess dedifferentiation, proliferation, and redifferentiation. Rats treated with 17β-estradiol had less kidney injury than did vehicle-treated rats post-IRI day 1. The number of PCNA-positive (PCNA) cells was significantly higher in post-IRI kidneys on day 1 in 17β-estradiol-treated rats. Moreover, vimentin and E-cadherin cells, which were interpreted as regeneration markers, were expressed earlier and significantly more copiously in 17β-estradiol-treated rats. We hypothesize that 17β-estradiol attenuates IRI-induced AKI by reducing inflammation and accelerating injured tubular cell regeneration.

Basic mechanisms of vascularization in endometriosis and their clinical implications

BACKGROUND

Vascularization is a major hallmark in the pathogenesis of endometriosis. An increasing number of studies suggests that multiple mechanisms contribute to the vascularization of endometriotic lesions, including angiogenesis, vasculogenesis and inosculation.

OBJECTIVE AND RATIONALE

In this review, we provide an overview of the basic mechanisms of vascularization in endometriosis and give special emphasis on their future clinical implications in the diagnosis and therapy of the disease.

SEARCH METHODS

Literature searches were performed in PubMed for English articles with the key words 'endometriosis', 'endometriotic lesions', 'angiogenesis', 'vascularization', 'vasculogenesis', 'endothelial progenitor cells' and 'inosculation'. The searches included both animal and human studies. No restriction was set for the publication date.

OUTCOMES

The engraftment of endometriotic lesions is typically associated with angiogenesis, i.e. the formation of new blood vessels from pre-existing ones. This angiogenic process underlies the complex regulation by angiogenic growth factors and hormones, which activate intracellular pathways and associated signaling molecules. In addition, circulating endothelial progenitor cells (EPCs) are mobilized from the bone marrow and recruited into endometriotic lesions, where they are incorporated into the endothelium of newly developing microvessels, referred to as vasculogenesis. Finally, preformed microvessels in shed endometrial fragments inosculate with the surrounding host microvasculature, resulting in a rapid blood supply to the ectopic tissue. These vascularization modes offer different possibilities for the establishment of novel diagnostic and therapeutic approaches. Angiogenic growth factors and EPCs may serve as biomarkers for the diagnosis and classification of endometriosis. Blood vessel formation and mature microvessels in endometriotic lesions may be targeted by means of anti-angiogenic compounds and vascular-disrupting agents.

WIDER IMPLICATIONS

The establishment of vascularization-based approaches in the management of endometriosis still represents a major challenge. For diagnostic purposes, reliable angiogenic and vasculogenic biomarker panels exhibiting a high sensitivity and specificity must be identified. For therapeutic purposes, novel compounds selectively targeting the vascularization of endometriotic lesions without inducing severe side effects are required. Recent progress in the field of endometriosis research indicates that these goals may be achieved in the near future.

Pitavastatin nanoparticle-engineered endothelial progenitor cells repair injured vessels

Endothelial progenitor cells (EPC) participate in vessel recovery and maintenance of normal endothelial function. Therefore, pitavastatin-nanoparticles (NPs)-engineered EPC may be effective in repairing injured vasculature. Pitavastatin-loaded poly(lactic-co-glycolic) acid (PLGA) NPs were obtained via ultrasonic emulsion solvent evaporation with PLGA as the carrier encapsulating pitavastatin. The effects and mechanism of pitavastatin-NPs on EPC proliferation in vitro were evaluated. Then, EPC that internalized pitavastatin-NPs were transplanted into rats after carotid artery injury. EPC homing, re-endothelialization, and neointima were evaluated by fluorescence labeling, evans Blue and hematoxylin/eosin (H&E) staining. Pitavastatin-NPs significantly improved EPC proliferation compared with control and pitavastatin group. Those effects were blocked by pretreatment with the pharmacological phosphoinositide 3-kinase (PI3K) blockers LY294002. After carotid artery injury, more transplanted EPC were detected in target zone in Pitavastatin-NPs group than pitavastatin and control group. Re-endothelialization was promoted and intimal hyperplasia was inhibited as well. Thus, pitavastatin-NPs promote EPC proliferation via PI3K signaling and accelerate recovery of injured carotid artery.

VEGF promotes endothelial progenitor cell differentiation and vascular repair through connexin 43

Background

Endothelial progenitor cell (EPC) differentiation is considered crucial for vascular repair. Vascular endothelial growth factor (VEGF) induces EPC differentiation, but the underlying mechanism of this phenomenon remains unclear. Connexin 43 (Cx43) is reported to be involved in the regulation of stem cell differentiation. Therefore, we sought to determine whether Cx43 is involved in VEGF-induced EPC differentiation and vascular repair.

Methods

Rat spleen-derived EPCs were cultured and treated with various concentrations of VEGF (0, 10, or 50 ng/mL), and the relationship between EPC differentiation and Cx43 expression was evaluated. Thereafter, fluorescence redistribution after photobleaching was performed to assess the relationship between adjacent EPC differentiation and Cx43-induced gap junction intercellular communication (GJIC). After carotid artery injury, EPCs pretreated with VEGF were injected into the tail veins, and the effects of Cx43 on vascular repair were evaluated.

Results

EPCs cultured with VEGF exhibited accelerated differentiation and increased expression of Cx43. However, inhibition of Cx43 expression using short interfering RNA (siRNA) attenuated EPC GJIC and consequent EPC differentiation. VEGF-pretreated EPC transplantation promoted EPC homing and reendothelialization, and inhibited neointimal formation. These effects were attenuated by siRNA inhibition of Cx43.

Conclusions

Our results from in vivo and in vitro experiments indicated that VEGF promotes EPC differentiation and vascular repair through Cx43.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0684-1) contains supplementary material, which is available to authorized users.

Cigarette Smoke Extract Changes Expression of Endothelial Nitric Oxide Synthase (eNOS) and p16(INK4a) and is Related to Endothelial Progenitor Cell Dysfunction

BACKGROUND Endothelial dysfunction is an important pathophysiologic feature in many smoke-related diseases. Endothelial progenitor cells (EPCs) are the precursors of endothelial cells and play a fundamental role in the maintenance of endothelial integrity and function. Endothelial nitric oxide synthase (eNOS) is the dominant NOS isoform in the vasculature and plays a central role in the maintenance of endothelial homeostasis. p16(INK4a) is a cyclin-dependent kinase inhibitor and could be regarded as a major dominant senescence gene. The present study aimed to determine whether the expression of eNOS and p16(INK4a) in EPCs is related to EPCs function and the possible epigenetic mechanism, if any. MATERIAL AND METHODS We investigated EPCs capacity for proliferation, adhesion, and secretion, and the expression of eNOS and p16(INK4a) in EPCs which were altered by cigarette smoke extract (CSE) in vitro. Furthermore, Decitabine (Dec), an agent of demethylation, was used to examine whether it could alter the changes induced by CSE. RESULTS The present study demonstrated that EPCs altered by CSE in vitro displayed decreased capacities of proliferation, adhesion, and secretion, which was accompanied by decreased eNOS expression and increased p16(INK4a) expression in EPCs. Furthermore, Dec could alleviate the changes in the expression of eNOS and p16(INK4a), and protect against the EPCs dysfunction caused by CSE. CONCLUSIONS The decreased eNOS expression and increased p16(INK4a) expression was associated with dysfunction of EPCs caused by CSE. The mechanism of methylation, one of the most common epigenetic mechanism, may be involved in the EPCs dysfunction caused by CSE.

Pivotal Cytoprotective Mediators and Promising Therapeutic Strategies for Endothelial Progenitor Cell-Based Cardiovascular Regeneration

Cardiovascular diseases (CVDs), including atherosclerosis, stroke, and myocardial infarction, is a major cause of death worldwide. In aspects of cell therapy against CVD, it is generally accepted that endothelial progenitor cells (EPCs) are potent neovascular modulators in ischemic tissues. In response to ischemic injury signals, EPCs located in a bone marrow niche migrate to injury sites and form new vessels by secreting various vasculogenic factors including VEGF, SDF-1, and FGF, as well as by directly differentiating into endothelial cells. Nonetheless, in ischemic tissues, most of engrafted EPCs do not survive under harsh ischemic conditions and nutrient depletion. Therefore, an understanding of diverse EPC-related cytoprotective mediators underlying EPC homeostasis in ischemic tissues may help to overcome current obstacles for EPC-mediated cell therapy for CVDs. Additionally, to enhance EPC's functional capacity at ischemic sites, multiple strategies for cell survival should be considered, that is, preconditioning of EPCs with function-targeting drugs including natural compounds and hormones, virus mediated genetic modification, combined therapy with other stem/progenitor cells, and conglomeration with biomaterials. In this review, we discuss multiple cytoprotective mediators of EPC-based cardiovascular repair and propose promising therapeutic strategies for the treatment of CVDs.

Estrogen Stimulates Homing of Endothelial Progenitor Cells to Endometriotic Lesions

The incorporation of endothelial progenitor cells (EPCs) into microvessels contributes to the vascularization of endometriotic lesions. Herein, we analyzed whether this vasculogenic process is regulated by estrogen. Estrogen- and vehicle-treated human EPCs were analyzed for migration and tube formation. Endometriotic lesions were induced in irradiated FVB/N mice, which were reconstituted with bone marrow from FVB/N-TgN (Tie2/green fluorescent protein) 287 Sato mice. The animals were treated with 100 μg/kg β-estradiol 17-valerate or vehicle (control) over 7 and 28 days. Lesion growth, cyst formation, homing of green fluorescent protein(+)/Tie2(+) EPCs, vascularization, cell proliferation, and apoptosis were analyzed by high-resolution ultrasonography, caliper measurements, histology, and immunohistochemistry. Numbers of blood circulating EPCs were assessed by flow cytometry. In vitro, estrogen-treated EPCs exhibited a higher migratory and tube-forming capacity when compared with controls. In vivo, numbers of circulating EPCs were not affected by estrogen. However, estrogen significantly increased the number of EPCs incorporated into the lesions' microvasculature, resulting in an improved early vascularization. Estrogen further stimulated the growth of lesions, which exhibited massively dilated glands with a flattened layer of stroma. This was mainly because of an increased glandular secretory activity, whereas cell proliferation and apoptosis were not markedly affected. These findings indicate that vasculogenesis in endometriotic lesions is dependent on estrogen, which adds a novel hormonally regulated mechanism to the complex pathophysiology of endometriosis.

Inhibition of Store-Operated Calcium Entry Protects Endothelial Progenitor Cells from H2O2-Induced Apoptosis

Store-operated calcium entry (SOCE), a major mode of extracellular calcium entry, plays roles in a variety of cell activities. Accumulating evidence indicates that the intracellular calcium ion concentration and calcium signaling are critical for the responses induced by oxidative stress. The present study was designed to investigate the potential effect of SOCE inhibition on H₂O₂-induced apoptosis in endothelial progenitor cells (EPCs), which are the predominant cells involved in endothelial repair. The results showed that H₂O₂-induced EPC apoptosis was reversed by SOCE inhibition induced either using the SOCE antagonist ML-9 or via silencing of stromal interaction molecule 1 (STIM1), a component of SOCE. Furthermore, SOCE inhibition repressed the increases in intracellular reactive oxygen species (ROS) levels and endoplasmic reticulum (ER) stress and ameliorated the mitochondrial dysfunction caused by H₂O₂. Our findings provide evidence that SOCE inhibition exerts a protective effect on EPCs in response to oxidative stress induced by H₂O₂ and may serve as a potential therapeutic strategy against vascular endothelial injury.

Transplantation of cryopreserved human umbilical cord blood-derived endothelial progenitor cells induces recovery of carotid artery injury in nude rats

Introduction

Transplantation of endothelial progenitor cells (EPCs) restores endothelial function in patients with endothelial dysfunction and initial denudation. The goal of the present study was to determine the effect of cryopreserved human umbilical cord blood (UCB)-derived EPC infusion on the repair of carotid artery injury in nude rats.

Methods

Mononuclear cells (MNCs) from human cryopreserved UCB and peripheral blood (PB) of patients with cardiovascular diseases and healthy volunteers were cultured in a conditioned medium. The in vitro migration, proliferation, adhesion, and survival capacities, as well as paracrine cytokine release of EPCs were investigated. EPC homing, induced reendothelialization, and the effect on neointima formation were also assessed in vivo.

Results

Patient-derived PB EPCs (PPB-EPCs) displayed decreased migration, proliferation, adhesion, and survival capabilities as compared to PB-EPCs from healthy volunteers (HPB-EPCs) and cryopreserved UCB-EPCs. However, there was no difference in the release of vascular endothelial growth factor (VEGF) and stromal cell derived factor 1 (SDF-1) between the three groups. Two weeks after transplantation, more labeled UCB-EPCs and HPB-EPCs than PPB-EPCs were found by cell tracking in the injury zone. Administration of PPB-EPCs, HPB-EPCs, and UCB-EPCs enhanced reendothelialization and inhibited neointima formation compared to the saline control. However, UCB-EPC and HPB-EPC infusion showed a greater improvement than PPB-EPCs.

Conclusions

Cryopreserved UCB-MNCs derived EPCs and HPB-EPCs show better responses to cytokines and vascular injury than PPB-EPCs. Thus, cryopreservation and delivery of cryopreserved autogenous UCB-EPCs or HPB-EPCs may be a promising vasculoprotective approach for patients with multiple cardiovascular risk factors.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0022-4) contains supplementary material, which is available to authorized users.

Deletion of Fgfr1 in osteoblasts enhances mobilization of EPCs into peripheral blood in a mouse endotoxemia model

Endothelial progenitor cells (EPCs) contribute to neovascularization and vascular repair, and may exert a beneficial effect on the clinical outcome of sepsis. Osteoblasts act as a component of "niche" in bone marrow, which provides a nest for stem/progenitor cells and are involved in the formation and maintenance of stem/progenitor cells. Fibroblast growth factor receptor 1 (FGFR1) can regulate osteoblast activity and influence bone mass. So we explored the role of FGFR1 in EPC mobilization. Male mice with osteoblast-specific knockout of Fgfr1 (Fgfr1(fl/fl);OC-Cre) and its wild-type littermates (Fgfr1(fl/fl) ) were used in this study. Mice intraperitoneally injected with lipopolysaccharide (LPS) were used to measure the number of circulating EPCs in peripheral blood and serum stromal cell-derived factor 1α (SDF-1α). The circulating EPC number and the serum level of SDF-1α were significantly higher in Fgfr1(fl/fl);OC-Cre mice than those in Fgfr1(fl/fl) mice after LPS injection. In cell culture system, SDF-1α level was also significantly higher in Fgfr1(fl/fl);OC-Cre osteoblasts compared with that in Fgfr1(fl/fl) osteoblasts after LPS treatment. TRAP staining showed that there was no significant difference between the osteoclast activity of septic Fgfr1(fl/fl) and Fgfr1(fl/fl);OC-Cre mice. This study suggests that targeted deletion of Fgfr1 in osteoblasts enhances mobilization of EPCs into peripheral blood through up-regulating SDF-1α secretion from osteoblasts.

Effects of dihydrotestosterone on adhesion and proliferation via PI3-K/Akt signaling in endothelial progenitor cells

The protective effects of male hormones on the cardiovascular system are still in dispute. There is now ample evidence that testosterone level is negatively correlated to the incidence and mortality of cardiovascular disease in men. Endothelial progenitor cells (EPCs) play a vital role in endothelial healing and vascular integrity, which are useful for promoting cardiovascular health. In this study, we investigated the effects of dihydrotestosterone (DHT), a non-aromatizable androgen, on human EPC function and the activation of the phosphatidylinositol-3-kinase (PI3-K)/Akt pathway in vitro. EPCs were incubated with a series of concentrations (1, 10, or 100 nmol/L in DMSO) of DHT for 24 h or with 10 nmol/L DHT for different time (6, 12, 24, 48 h). EPC adhesion and proliferation and the activation of Akt were assayed by cell counting, 5-ethynyl-2'-deoxyuridine incorporation assay, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and Western blot analysis. Our data demonstrated that DHT significantly increased the proliferative activity and adhesive ability of EPCs in a dose- and time-dependent manner, maximum at 10 nmol/L, 24 h (p < 0.05). Western blot analysis revealed that DHT promoted the phosphorylation of Akt, and the effects of different concentrations of DHT on Akt phosphorylation were consistent with those on EPC proliferation and adhesion (p < 0.05). However, the enhancing effects of DHT on EPCs decreased with administration of the pharmacological PI3-K blocker LY294002 (p < 0.05). In conclusion, DHT can modulate EPC proliferation and adhesion and the PI3-K/Akt pathway plays an important role in this process.

Activation of liver X receptor enhances the proliferation and migration of endothelial progenitor cells and promotes vascular repair through PI3K/Akt/eNOS signaling pathway activation

Vascular endothelial injury is a major cause of many cardiovascular diseases. The proliferation and migration of endothelial progenitor cells (EPCs) play a pivotal role in endothelial regeneration and repair after vascular injury. Recently, liver X receptor (LXR) activation has been suggested as a potential target for novel therapeutic interventions in the treatment of cardiovascular disease. However, the effects of LXR activation on endothelial regeneration and repair, as well as EPC function, have not been investigated. In the present study, we demonstrate that LXRs, including LXRα and LXRβ, are expressed and functional in rat bone marrow-derived EPCs. Treatment with an LXR agonist, TO901317 (TO) or GW3965 (GW), significantly increased the proliferation and migration of EPCs, as well as Akt and eNOS phosphorylation in EPCs. Moreover, LXR agonist treatment enhanced the expression and secretion of vascular endothelial growth factor in EPCs. LXR agonists accelerated re-endothelialization in injured mouse carotid arteries in vivo. These data confirm that LXR activation may improve EPC function and endothelial regeneration and repair after vascular injury by activating the PI3K/Akt/eNOS pathway. We conclude that LXRs may be attractive targets for drug development in the treatment of cardiovascular diseases associated with vascular injury.

Dual effects of cigarette smoke extract on proliferation of endothelial progenitor cells and the protective effect of 5-aza-2'-deoxycytidine on EPCs against the damage caused by CSE

Cigarette smoke is a major public health problem associated with multitude of diseases, including pulmonary and vascular diseases. Endothelial progenitor cells (EPCs) contribute to neovascularization and play an important role in the development of these diseases. The effect of CSE on EPCs is seldom studied. The aim of the current study is to observe the effect of CSE on biological behavior of EPCs and, further, to search for potential candidate agent in protection of proliferation of EPCs against the damage caused by CSE exposure in vitro. Methods. The proliferations of EPCs isolated from bone marrow of C57BL/6J mice were assessed by MTT after incubating the EPCs with a series of concentrations of CSE (1.0%, 2.5%, 5.0%, and 10.0%) for different times (3, 6, and 24 hours) as well as with 1.0% CSE in presence of 5-AZA-CdR for 24 hours. Results. The proliferations of EPCs were significantly enhanced after 3 hours of exposure to concentrations of 1.0% and 2.5% CSE but depressed when exposed to concentrations of 5.0% and 10.0% CSE. Furthermore, the 5-AZA-CdR in concentrations of 2.0 μmol/L and 5.0 μmol/L partly protected against the depression of proliferation of EPCs caused by CSE exposure. Conclusions. The CSE showed dual effects on proliferation of EPCs isolated from mice. The 5-AZA-CdR partly protected the proliferation of EPCs against the damage caused by CSE exposure in vitro, suggesting that DNA methylation may be involved in the dysfunction of EPCs induced by CSE.

10(-7) m 17β-oestradiol enhances odonto/osteogenic potency of human dental pulp stem cells by activation of the NF-κB pathway

OBJECTIVES

Oestrogen has been proven to significantly enhance osteogenic potency, while oestrogen deficiency usually leads to impaired osteogenic differentiation of mesenchymal stem cells. However, little is known concerning direct effects of oestrogen on differentiation of human dental pulp stem cells (DPSCs).

MATERIALS AND METHODS

In this study, human DPSCs were isolated and treated with 10(-7)  m 17β-oestradiol (E2). Alkaline phosphatase (ALP) assay and alizarin red staining were performed.

RESULTS

Alkaline phosphatase and alizarin red showed that E2 treatment significantly enhanced ALP activity and mineralization ability of DPSCs, but had no effect on cell proliferation. Real-time RT-PCR and western blot assay demonstrated that odonto/osteogenic markers (ALP, RUNX2/RUNX2, OSX/OSX, OCN/OCN and DSPP/DSP) were significantly upregulated in the cells after E2 treatment. Moreover, phosphorylation of cytoplasmic IκBα/P65 and expression of nuclear P65 were enhanced in a time-dependent manner following E2 treatment, suggesting activation of NF-κB signaling. Conversely, inhibition of the NF-κB pathway suppressed E2-mediated upregulation of odonto/osteogenic markers, indicating that the NF-κB pathway was pivotal for E2-mediated differentiation.

CONCLUSION

These findings provide evidence that 10(-7)  m 17β-oestradiol promoted odonto/osteogenic differentiation of human DPSCs via activation of the NF-κB signaling pathway.

Vasculogenesis of decidua side population cells of first-trimester pregnancy

INTRODUCTION

Sufficient uterine blood supply is essential for the fetus to develop normally in the uterus. Several mechanisms are involved in the process of vessel development in deciduas and villus. We focus on whether first-trimester decidua side population (SP) cells contain cells capable of differentiating into endothelial cells.

METHODS

Eight decidua samples were collected from healthy women, 22- to 30-years old, undergoing elective terminations of early pregnancy (six to eight gestational weeks). The cell suspensions from human deciduas were stained by Hoechst 33342 and sorted by flow cytometry, further cultured under differentiation conditions and analyzed for specific markers. These cells were implanted into ischemic limbs of nude mice to test the capacity of angiogenesis in vivo by DiI tracers and immunohistochemistry.

RESULTS

Decidua CD31(-)CD146(-) SP cells of first-trimester human pregnancy can differentiate into endothelial cells, express the corresponding specific markers of endothelial cells, such as CD31 and CD146, and form tube-like structures on Matrigel and part of newly formed vessels in the ischemic limbs of nude mice. Vascular endothelial growth factor was more effective in promoting proliferation of CD31(-)CD146(-)SP cells compared with other growth factors, and estrogen and progesterone at a final concentration of 10 μmol/L and 30 μmol/L, respectively, promoted the migration of CD31()-CD146(-)SP cells in a dose-dependent manner.

CONCLUSIONS

CD31(-)CD146(-) SP cells may be involved in the formation of new vessels in the maternal aspect of the placenta in the first trimester.

Overexpression of SDF-1α enhanced migration and engraftment of cardiac stem cells and reduced infarcted size via CXCR4/PI3K pathway

Cardiac stem cells (CSCs) can home to the infarcted area and regenerate myocardium. Stromal cell-derived factor-1α/C-X-C chemokine receptor type 4 (SDF-1α/CXCR4) axis is pivotal in inducing CSCs migration. However, the mechanisms remain unclear. This study set out to detect if SDF-1α promotes migration and engraftment of CSCs through the CXCR4/PI3K (phosphatidylinositol 3-kinase) pathway. In the in vitro experiment, c-kit+ cells were isolated from neonatal mouse heart fragment culture by magnetic cell sorting. Fluorescence-activated cell sorting results demonstrated that a few c-kit+ cells expressed CD45 (4.54%) and Sca-1 (2.58%), the hematopoietic stem cell marker. Conditioned culture could induce c-kit+ cells multipotent differentiation, which was confirmed by cardiac troponin I (cTn-I), α-smooth muscle actin (α-SMA), and von Willebrand factor (vWF) staining. In vitro chemotaxis assays were performed using Transwell cell chambers to detect CSCs migration. The results showed that the cardiomyocytes infected with rAAV1-SDF-1α-eGFP significantly increased SDF-1α concentration, 5-fold more in supernatant than that in the control group, and subsequently attracted more CSCs migration. This effect was diminished by administration of AMD3100 (10 µg/ml, CXCR4 antagonist) or LY294002 (20 µmol/L, PI3K inhibitor). In myocardial infarction mice, overexpression of SDF-1α in the infarcted area by rAAV1-SDF-1α-eGFP infection resulted in more CSCs retention to the infarcted myocardium, a higher percentage of proliferation, and reduced infarcted area which was attenuated by AMD3100 or ly294002 pretreatment. These results indicated that overexpression of SDF-1α enhanced CSCs migration in vitro and engraftment of transplanted CSCs and reduced infarcted size via CXCR4/PI3K pathway.

Rapid actions of plasma membrane estrogen receptors regulate motility of mouse embryonic stem cells through a profilin-1/cofilin-1-directed kinase signaling pathway

Long-term estrogen actions are vital for driving cell growth, but more recent evidence suggests that estrogen mediates more rapid cellular effects. However, the function of estradiol-17β (E(2))-BSA in mouse embryonic stem cells has not been reported. Therefore, we examined the role of E(2)-BSA in mouse embryonic stem cell motility and its related signal pathways. E(2)-BSA (10(-8) m) significantly increased motility after 24 h incubation and increased filamentous (F)-actin expression; these effects were inhibited by the estrogen receptor antagonist ICI 182,780, indicating that E(2)-BSA bound membrane estrogen receptors and initiated a signal. E(2)-BSA increased c-Src and focal adhesion kinase (FAK) phosphorylation, which was attenuated by ICI 182,780. The E(2)-BSA-induced increase in epidermal growth factor receptor (EGFR) phosphorylation was inhibited by Src inhibitor PP2. As a downstream signal molecule, E(2)-BSA activated cdc42 and increased formation of a complex with the neural Wiskott-Aldrich syndrome protein (N-WASP)/cdc42/transducer of cdc42-dependent actin assembly-1 (TOCA-1), which was inhibited by FAK small interfering RNA (siRNA) and EGFR inhibitor AG 1478. In addition, E(2)-BSA increased profilin-1 expression and cofilin-1 phosphorylation, which was blocked by cdc42 siRNA. Subsequently, E(2)-BSA induced an increase in F-actin expression, and cell motility was inhibited by each signal pathway-related siRNA molecule or inhibitors but not by cofilin-1 siRNA. A combined treatment of cofilin-1 siRNA and E(2)-BSA increased F-actin expression and cell motility more than that of E(2)-BSA alone. These data demonstrate that E(2)-BSA stimulated motility by interacting with profilin-1/cofilin-1 and F-actin through FAK- and c-Src/EGFR transactivation-dependent N-WASP/cdc42/TOCA-1 complex.

Over-expression of PDGFR-β promotes PDGF-induced proliferation, migration, and angiogenesis of EPCs through PI3K/Akt signaling pathway

The proliferation, migration, and angiogenesis of endothelial progenitor cells (EPCs) play critical roles in postnatal neovascularization and re-endothelialization following vascular injury. Here we evaluated whether the over-expression of platelet-derived growth factor receptor-β (PDGFR-β) can enhance the PDGF-BB-stimulated biological functions of EPCs through the PDGFR-β/phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. We first confirmed the expression of endogenous PDGFR-β and its plasma membrane localization in spleen-derived EPCs. We then demonstrated that the PDGFR-β over-expression in EPCs enhanced the PDGF-BB-induced proliferation, migration, and angiogenesis of EPCs. Using AG1295 (a PDGFR kinase inhibitor), LY294002 (a PI3K inhibitor), and sc-221226 (an Akt inhibitor), we further showed that the PI3K/Akt signaling pathway participates in the PDGF-BB-induced proliferation, migration, and angiogenesis of EPCs. In addition, the PI3K/Akt signaling pathway is required for PDGFR-β over-expression to enhance these PDGF-BB-induced phenotypes.

An essential role for the Id1/PI3K/Akt/NFkB/survivin signalling pathway in promoting the proliferation of endothelial progenitor cells in vitro

The enhancement of re-endothelialisation is a critical therapeutic option for repairing injured blood vessels. Endothelial progenitor cells (EPCs) are the major source of cells that participate in endothelium repair and contribute to re-endothelialisation by reducing neointima formation after vascular injury. The over-expression of the inhibitor of differentiation or DNA binding 1 (Id1) significantly improved EPC proliferation. This study aimed to investigate the effects of Id1 on the phosphatidylinositol-3-kinase (PI3K)/Akt/nuclear factor kappa B (NFκB)/survivin signalling pathway and its significance in promoting EPC proliferation in vitro. Spleen-derived EPCs were cultured as previously described. Id1 was presented at low levels in EPCs, and was rapidly up-regulated by stimulation with vascular endothelial growth factor. We demonstrated that transient transfection of Id1 into EPCs activated the PI3K/Akt/NFκB/survivin signalling pathway and promoted EPC proliferation. The proliferation of EPCs was extensively inhibited by silencing of endogenous Id1, and knockdown of Id1 expression led to suppression of PI3K/Akt/NFκB/survivin signalling pathway in EPCs. In addition, blockade by the PI3K-specific inhibitor LY294002, Akt inhibitor, the NFκB inhibitor BAY 11-7082, the survivin inhibitor Curcumin, or the survivin inhibitor YM155 reduced the effects of Id1 transfection. These results suggest that the Id1/PI3K/Akt/NFκB/survivin signalling pathway plays a critical role in EPC proliferation. The Id1/PI3K/Akt/NFκB/survivin signalling pathway may represent a novel therapeutic target in the prevention of restenosis after vascular injury.

Estrogen and antiestrogens alter breast cancer invasiveness by modulating the transforming growth factor-β signaling pathway

In the later stages of breast cancer, estrogen receptor (ER)α-negative cancers typically have higher histological grades than ERα-positive cancers, and transforming growth factor (TGF)-β promotes invasion and metastasis. Our previous study indicated that ERα inhibited TGF-β signaling by inducing the degradation of Smad in an estrogen-dependent manner. In the present study, we report that the suppressive effects of ERα and estrogen on tumor progression are mediated by inhibiting TGF-β signaling. Furthermore, we investigated the effects of antiestrogens such as ICI182,780 (ICI) or tamoxifen (TAM) on TGF-β signaling and breast cancer invasiveness. The levels of total Smad and pSmad were reduced by estrogen, whereas ICI slightly increased them, and TAM had no effect. To investigate the effect of antiestrogens on breast cancer invasiveness, we generated highly migratory and invasive MCF-7-M5 cells. The migration and invasion of these cells were suppressed by the inhibitor of TGF-β receptor kinase, SB-505124, and estrogen. However, antiestrogens did not suppress the migration and invasion of these cells. In addition, we screened TGF-β target genes whose expression was reduced by estrogen treatment and identified four genes associated with breast cancer invasiveness and poor prognosis. The expression of these genes was not decreased by antiestrogens. These observations provide a new insight into estrogen function and the mechanisms underlying estrogen-mediated suppression of tumor progression.

Endothelial progenitor cell biology in disease and tissue regeneration

Endothelial progenitor cells are increasingly being studied in various diseases ranging from ischemia, diabetic retinopathy, and in cancer. The discovery that these cells can be mobilized from their bone marrow niche to sites of inflammation and tumor to induce neovasculogenesis has afforded a novel opportunity to understand the tissue microenvironment and specific cell-cell interactive pathways. This review provides a comprehensive up-to-date understanding of the physiological function and therapeutic utility of these cells. The emphasis is on the systemic factors that modulate their differentiation/mobilization and survival and presents the challenges of its potential therapeutic clinical utility as a diagnostic and prognostic reagent.

Knockdown of transient receptor potential canonical-1 reduces the proliferation and migration of endothelial progenitor cells

Endothelial progenitor cells (EPCs) play an important role in accelerating endothelial repair after vascular injury. The proliferation and migration of EPCs is a critical first step in restoring endothelial. However, mechanisms for modulating EPC proliferation and migration are still being elucidated. Our previous study found that transient receptor potential canonical-1 (TRPC1) is involved in regulating store-operated Ca(2+) entry in EPCs through stromal interaction molecule 1. Therefore, in the present study, we sought to further investigate the regulation of proliferation and migration of EPCs by TRPC1. We found that the silencing of TRPC1 by 2 different RNA interference methods suppressed the proliferation and migration of EPCs. In addition, knockdown of TRPC1 significantly reduced of the amplitude of store-operated Ca(2+) entry and caused arrest of the EPC cell cycle in G1 phase. Analysis of the expression of 84 cell cycle genes by microarray showed that 9 genes were upregulated and 4 were downregulated by >2-fold in EPCs following TRPC1 silencing. The genes with expression changes were Ak1, Brca2, Camk2b, p21, Ddit3, Inha, Slfn1, Mdm2, Prm1, Bcl2, Mki67, Pmp22, and Ppp2r3a. Finally, we found that a Schlafen 1-blocking peptide partially reversed the abnormal cell cycle distribution and proliferation induced by TRPC1 knockdown, suggesting that Schlafen 1 is downstream of TRPC1 silencing in regulating EPC proliferation. In summary, these findings provide a new mechanism for modulating the biological properties of EPCs and suggest that TRPC1 may be a new target for inducing vascular repair by EPCs.

E₂-BSA activates caveolin-1 via PI₃K/ERK1/2 and lysosomal degradation pathway and contributes to EPC proliferation

BACKGROUND

The mechanism that estrogen (E(2)) increases the number of endothelial progenitor cells (EPC) is largely unknown. Here we used E(2)-conjugated bovine serum albumin (E(2)-BSA, membrane impermeable) to investigate whether the membrane estrogen receptor (mER) and its related protein caveolin-1 (CAV-1) are involved in these processes.

METHODS AND RESULTS

E(2)-BSA promoted [(3)H]-thymidine incorporation of EPC through increasing CAV-1 expression via mER (ERα, but not ERβ or GPR30). Both cholesterol depletion and CAV-1 knockdown with use of CAV-1 siRNA significantly attenuated E(2)-BSA-induced [(3)H]-thymidine incorporation. Western blot showed that E(2)-BSA increased membrane CAV-1 protein expression 12h after treatment, whereas mRNA levels of CAV-1 were augmented until 24h after E(2)-BSA treatment. Furthermore, pre-incubated EPC with ICI 182780 (a specific ER antagonist), LY 294002 (a selective PI(3)K inhibitor) or PD 98059 (a specific ERK1/2 inhibitor) before E(2)-BSA inhibited the late-stage effect of E(2)-BSA (≥24 h) on up-regulation of CAV-1 mRNA and protein expression. Pulse chase results demonstrated that E(2)-BSA inhibited lysosome-mediated degradation of CAV-1 protein at the early stage (≤12 h), and then resulted in the increased CAV-1 protein.

CONCLUSION

In the present work we demonstrated that E(2)-BSA promotes EPC proliferation through mER (ERα) in CAV-1-dependent manner: prolonging the stability of CAV-1 protein through quick inhibition of the lysosomal degradation pathway at the early stage (≤12 h) and up-regulating CAV-1 at transcription levels through PI(3)K/ERK1/2 signaling pathway at the late stage (≥24 h). These data indicated that a there is a novel mechanism of E(2)-BSA in the regulation of EPC proliferation through CAV-1.

The spleen recruits endothelial progenitor cell via SDF-1/CXCR4 axis in mice

Endothelial progenitor cell (EPC) therapy represents a novel strategy for a variety of diseases. Interestingly, spleen acts an important reservoir during EPC trafficking. Therefore, we investigated the involvement of stromal cell-derived factor-1 (SDF-1)/CXCR4 in EPC settlement in the spleen. EPC were cultured and characterized as previous methods. Then, 1 x 10(6) EPC were labeled with DiI-LDL and intravenously infused into C57/BL6 mice. Immunohistochemical staining showed homing of transplanted EPC in the spleen 24 h later, indicating recruitment of transplanted EPC into the spleen. The distribution of EPC in different organs was evaluated by fluorescence-activated cell sorting of Sca-1/Flk-1(+) cells, which demonstrated settlement of EPC in the spleen. Removal of the splenic niche by splenectomy augmented circulating EPC 12 and 24 h later, indicating an important role of spleen on modulation of EPC-circulating dynamics. Expressions of SDF-1 in the spleen and CXCR4 in EPC were revealed by enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR). A modified Boyden chamber assay showed that SDF-1 (10 or 100 ng/mL) induced EPC migration in vitro. Injection of the SDF-1 protein into the spleen increased the number of splenic EPC. In contrast, injection of a SDF-1 antibody or AMD3100 (SDF-1/CXCR4 axis antagonist) attenuated their settlement and did not induce EPC apoptosis. These results indicate that the SDF-1/CXCR4 axis is involved in recruitment of EPC to the spleen, and enhances our understanding of EPC-circulating kinetics.

Potential manipulation of endothelial progenitor cells in diabetes and its complications

Diabetes mellitus increases cardiovascular risk through its negative impact on vascular endothelium. Although glucotoxicity and lipotoxicity account for endothelial cell damage, endothelial repair is also affected by diabetes. Endothelial progenitor cells (EPCs) are involved in the maintenance of endothelial homoeostasis and in the process of new vessel formation. For these reasons, EPCs are thought to have a protective impact within the cardiovascular system. In addition, EPCs appear to modulate the functioning of other organs, providing neurotropic signals and promoting repair of the glomerular endothelium. The exact mechanisms by which EPCs provide cardiovascular protection are unknown and the definition of EPCs is not standardized. Notwithstanding these limitations, the literature consistently indicates that EPCs are altered in type 1 and type 2 diabetes and in virtually all diabetic complications. Moreover, experimental models suggest that EPC-based therapies might help prevent or reverse the features of end-organ complications. This identifies EPCs as having a novel pathogenic role in diabetes and being a potential therapeutic target. Several ways of favourably modulating EPCs have been identified, including lifestyle intervention, commonly used medications and cell-based approaches. Herein, we provide a comprehensive overview of EPC pathophysiology and the potential for EPC modulation in diabetes.

Knockdown of stromal interaction molecule 1 attenuates hepatocyte growth factor-induced endothelial progenitor cell proliferation

Increased Ca(2+) entry through store-operated Ca(2+) channels (SOCCs) plays an essential role in the regulation of hepatocyte growth factor (HGF)-induced cell proliferation. Stromal interaction molecule 1 (STIM1) is thought to transmit endoplasmic reticulum (ER) Ca(2+) store depletion signals to the plasma membrane (PM), causing the opening of SOCCs in the PM. However, the relationship between HGF and STIM1 in endothelial progenitor cell (EPC) proliferation remains uncharacterized. The objective of this study was to evaluate the potential involvement of STIM1 in HGF-induced EPC proliferation. For this purpose, we used cultured rat bone marrow-derived EPCs and found that HGF-induced EPC proliferation at low concentrations. Store-operated Ca(2+) entry (SOCE) was elevated in HGF-treated EPCs, and the SOCC inhibitors 2-aminoethoxydiphenyl borate (2-APB) and BTP-2 inhibited the HGF-induced proliferation response. Moreover, STIM1 mRNA and protein expression levels were increased in response to HGF stimulation and knockdown of STMI1 decreased SOCE and prevented HGF-induced EPC proliferation. In conclusion, our data suggest that HGF-induced EPC proliferation is mediated partly via activation of STIM1.

Endothelial progenitor cells and spleen: new insights in regeneration medicine

As a promising concept for regeneration medicine, endothelial progenitor cell (EPC) therapy represents a novel strategy for a variety of diseases. Increasing evidence suggests that the spleen, a traditionally dispensable organ, acts as a major reservoir during EPC trafficking and plays an important role regarding the modulation of circulating EPC kinetics. Moreover, infusion of splenic EPC can restore endothelial function and promote neovascularization, indicating an available resource for EPC transplantation. Thus a discussion of the role of the spleen with respect to EPC may provide novel information for management of EPC therapy.

Gender dimorphisms in progenitor and stem cell function in cardiovascular disease

Differences in cardiovascular disease outcomes between men and women have long been recognized and attributed, in part, to gender and sex steroids. Gender dimorphisms also exist with respect to the roles of progenitor and stem cells in post-ischemic myocardial and endothelial repair and regeneration. Understanding how these cells are influenced by donor gender and the recipient hormonal milieu may enable researchers to further account for the gender-related disparities in clinical outcomes as well as utilize the beneficial effects of these hormones to optimize transplanted cell function and survival. This review discusses (1) the cardiovascular effects of sex steroids (specifically estradiol and testosterone); (2) the therapeutic potentials of endothelial progenitor cells, mesenchymal stem cells, and embryonic stem cells; and (3) the direct effect of sex steroids on these cell types.

Cellular and molecular mechanisms of 17beta-estradiol postconditioning protection against gastric mucosal injury induced by ischemia/reperfusion in rats

AIMS

To investigate the protective effects of 17beta-estradiol postconditioning against ischemia/reperfusion (I-R)-induced gastric mucosal injury in rats.

MAIN METHODS

The animal model of gastric ischemia/reperfusion was established by clamping of the celiac artery for 30 min and reperfusion for 30 min, 1h, 3h, 6h, 12h or 24h. 17beta-estradiol at doses of 5, 50 or 100 microg/kg (rat) was administered via peripheral veins 2 min before reperfusion. In a subgroup of rats, the estrogen receptor antagonist fulvestrant (Ful, 2mg/kg) was intravenously injected prior to 17beta-estradiol administration. Histological and immunohistochemical methods were employed to assess the gastric mucosal injury index and gastric mucosal cell apoptosis and proliferation. The malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, xanthine oxidase (XOD) activity and hydroxyl free radical (-OH) inhibitory ability were determined by colorimetric assays. Subsequently, the expression of Bcl-2 and Bax in rat gastric mucosa was examined by western blotting.

KEY FINDINGS

17beta-estradiol dose-dependently inhibited gastric I-R (GI-R) injury, and 17beta-estradiol (50 microg/kg) markedly attenuated GI-R injury 1h after reperfusion. 17beta-estradiol inhibited gastric mucosal cell apoptosis and promoted gastric mucosal cell proliferation in addition to increasing SOD activity and -OH inhibitory ability and decreasing the MDA content and XOD activity. The Bax protein level increased 1h after GI-R and was markedly reduced by intravenous administration of 17beta-estradiol. In contrast, the level of Bcl-2 protein decreased 1h after GI-R and was restored to normal levels by intravenous administration of 17beta-estradiol. These effects of 17beta-estradiol were inhibited by pretreatment with fulvestrant.

SIGNIFICANCE

17beta-estradiol postconditioning should be investigated further as a possible strategy against gastric mucosal injury.

Effects of androgens on endothelial progenitor cells in vitro and in vivo

The beneficial or detrimental effects of androgens on the cardiovascular system are debated. Endothelial progenitor cells are bone-marrow-derived cells involved in endothelial healing and angiogenesis, which promote cardiovascular health. Oestrogens are potent stimulators of endothelial progenitor cells, and previous findings have indicated that androgens may improve the biology of these cells as well. In the present study, we show that testosterone and its active metabolite dihydrotestosterone exert no effects on the expansion and function of late endothelial progenitors isolated from the peripheral blood of healthy human adult males, whereas they positively modulate early ‘monocytic’ endothelial progenitor cells. In parallel, we show that castration in rats is followed by a decrease in circulating endothelial progenitor cells, but that testosterone and dihydrotestosterone replacement fails to restore endothelial progenitor cells towards normal levels. This is associated with persistently low oestrogen levels after androgen replacement in castrated rats. In a sample of 62 healthy middle-aged men, we show that circulating endothelial progenitor cell levels are more directly associated with oestradiol, rather than with testosterone, concentrations. In conclusion, our results collectively demonstrate that androgens exert no direct effects on endothelial progenitor cell biology in vitro and in vivo.

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.

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.

Chronic green tea consumption decreases body mass, induces aromatase expression, and changes proliferation and apoptosis in adult male rat adipose tissue

Green tea (GT) and its components have been shown to possess antiobesity properties and the corresponding mechanisms of action are being investigated, given the epidemic proportions of obesity incidence. In the current work, we used 12-mo-old male Wistar rats to test the effect of 6 mo of treatment with GT as the sole drinking beverage (52.8 +/- 6.4 mL/d) on adipose tissue (AT). AT aromatase expression was determined by Western blotting, plasma concentrations of 17beta-estradiol and testosterone were determined by RIA, and adipocyte size determined by measuring diameter in tissue sections. Proliferation and apoptosis were also assessed by Ki67 immunostaining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling, respectively. Evaluations were made in subcutaneous (sc) AT and visceral (v) AT. Body weight increased over time in both groups (P < 0.001), but the increase was more pronounced in controls (P < 0.001) and food and fluid intake did not influence that effect. At the end of the experiment, aromatase expression increased in the AT (318.5 +/- 60.6% of control in scAT, P < 0.05, and 285.5 +/- 82.9% of control in vAT, P < 0.01). AT of GT-treated rats had a higher percentage of proliferating cells (204.1 +/- 19.5% of control in scAT, P < 0.01, and 246.6 +/- 50.2% of control in vAT, P < 0.01) and smaller adipocytes (78.3 +/- 1.7% of control in scAT, P < 0.001, and 87.9 +/- 3.2% of control in vAT, P < 0.05). GT also increased the number of apoptotic cells in vAT (320.4 +/- 21.9% of control; P < 0.001). These results suggest new mechanisms for GT on body weight and highlight its potential benefit to prevent or treat obesity and the metabolic syndrome.

Role of estrogen receptors in menstrual cycle-related neoangiogenesis and their influence on endothelial progenitor cell physiology

OBJECTIVE

To study whether estrogen receptors (ERs) are expressed in vitro and in vivo by female circulating endothelial progenitor cells (EPCs); and the role of ERs in the periodic vascular damage and repair that occurs during the menstrual cycle.

DESIGN

Quantification of circulating progenitor cells, EPCs, and relative CXCR4+ fraction by flow cytometry. Quantification of plasma 17beta-E(2) by electrochemiluminescent immunoassay. Expression of ERs by immunofluorescence and immunohistochemistry. Estrogen receptor, CXCR4, and matrix metalloproteinase 9 gene expression by reverse transcriptase-polymerase chain reaction and real-time polymerase chain reaction.

SETTING

University clinic and academic research laboratory.

PATIENT(S)

Twelve young fertile women (aged 22-27 years) observed for 6 months, 10 postmenopausal women (aged 52-63 years), and 50 male control subjects (aged 24-61 years).

INTERVENTION(S)

Blood (35 mL) was collected at each observation point.

MAIN OUTCOME MEASURE(S)

Correlation between 17beta-E(2) exposure and neoangiogenesis markers.

RESULT(S)

Estrogen receptors are expressed both in cultured EPCs after prolonged estrogen stimulation and in circulating EPCs, such as in CD34+ cells in bone marrow. The number of ER-beta+ and CXCR4+ EPCs increased during the ovulatory phase, and this increase is probably mediated by ER-beta and matrix metalloproteinase 9.

CONCLUSION(S)

Estrogens play a key role in neoangiogenesis processes, such as endometrium recovery, and this mechanism involves both a central action (on bone marrow) and a cytokine-mediated peripheral one (on endothelium).

Vascular effects of estrogen and progestins and risk of coronary artery disease: importance of timing of estrogen treatment

The effects of estrogen and progestins on the vascular wall have drawn major medical attention, and significant controversy over various studies has been developed. Several experimental and observational studies have shown cardioprotective effects; however, prospective randomized trials showed an increase in cardiovascular events in postmenopausal women on estrogen/ medroxyprogesterone acetate treatment. The most significant parameter for cardiovascular benefit of estrogen seems to be the interval since the onset of menopause. In the early postmenopausal years, estrogen has beneficial effects on the vascular wall by inhibition of atherosclerosis progression, whereas in the late postmenopause, adverse effects like upregulation of the plaque inflammatory processes and plaque instability may develop. The effects of progestins on the cardiovascular system are not as clear and may differ according to the choice of progestins that is used. The aim of this review is to summarize the effects of estrogen and progestins on the vascular wall and their clinical implications.

The proliferative effect of estradiol on human prostate stromal cells is mediated through activation of ERK

BACKGROUND

Estrogen is involved in the development and progression of benign prostatic hyperplasia (BPH). It can stimulate proliferation of prostate stromal cells (PrSCs). However, the exact mechanism remains unclear.

METHODS

We used the primary cultured human PrSCs and a prostate stromal cell line, WPMY-1, to examine the signaling pathways involved in estrogen-mediated proliferation of PrSCs. Cells were treated with 17beta-estradiol (E(2)) or BSA-E(2). Cell proliferation was assessed by the MTT assay and by cell counting. Western blot analysis was used to determine the status of activation of ERK1/2.

RESULTS

Results indicated that both E(2) and BSA-E(2) stimulated proliferation of primary PrSCs and WPMY-1 cells. ERK was rapidly activated by E(2) and BSA-E(2). PD98059, which is a selective ERK inhibitor, significantly inhibited estrogen-induced cell proliferation. PrSCs expressed estrogen receptor alpha (ERalpha) and GPR30 but not ERbeta. Small hairpin RNA (shRNA) to ERalpha, but not to GPR30, blocked estrogen-mediated ERK activation and cell proliferation.

CONCLUSIONS

The results indicated that estrogen could activate ERK pathway through the non-genomic ERalpha pathway, leading to proliferation of PrSCs.

Pulmonary gas transfer related to markers of angiogenesis during the menstrual cycle

Gas transfer in the female lung varies over the menstrual cycle in parallel with the cyclic angiogenesis that occurs in the uterine endometrium. Given that vessels form and regress in the uterus under the control of hormones, angiogenic factors, and proangiogenic circulating bone marrow-derived progenitor cells, we tested the possibility that variation in pulmonary gas transfer over the menstrual cycle is related to a systemic cyclic proangiogenic state that influences lung vascularity. Women were evaluated over the menstrual cycle with weekly measures of lung diffusing capacity and its components, the pulmonary vascular capillary bed and membrane diffusing capacity, and their relation to circulating CD34(+)CD133(+) progenitor cells, hemoglobin, factors affecting hemoglobin binding affinity, and proangiogenic factors. Lung diffusing capacity varied over the menstrual cycle, reaching a nadir during the follicular phase following menses. The decline in lung diffusing capacity was accounted for by approximately 25% decrease in pulmonary capillary blood volume. In parallel, circulating CD34(+)CD133(+) progenitor cells decreased by approximately 24% and were directly related to angiogenic factors and to lung diffusing capacity and pulmonary capillary blood volume. The finding of a greater number of lung microvessels in ovariectomized female mice receiving estrogen compared with placebo verified that pulmonary vascularity is influenced by hormonal changes. These findings suggest that angiogenesis in the lungs may participate in the cyclic changes in gas transfer that occur over the menstrual cycle.