Endothelial Progenitor Cells Apoptosis Research Articles

Soluble thrombomodulin is a paracrine anti-apoptotic factor for vascular endothelial protection

BackgroundThrombomodulin (TM) is an endothelial cell (EC) membrane-bound anticoagulant protein that has novel direct cellular effects. TM is shed from EC and becomes soluble form (sTM) in plasma. Higher sTM levels in healthy subjects are associated with lower cardiovascular risk, suggesting that sTM possesses a protective role. The purpose of the study was to evaluate the effect of sTM on vascular endothelium. Methods and resultsApoptosis of cultured ECs was induced via serum starvation. EC-bound TM was released into the medium after serum starvation. The medium conditioned by serum-starved EC decreased apoptosis in another set of cultured EC. Direct treatment with sTM reduced EC apoptosis and decreased pro-apoptotic protein expression. TM knockdown in EC exacerbated the rate of serum starvation-induced apoptosis. Treatment of sTM activated the phosphatidylinositol 3-kinase (PI3 kinase)–protein kinase B/Akt survival pathway and suppressed the death pathway, c-Jun N-terminal kinase. We found that sTM also increased growth and reduced apoptosis of endothelial progenitor cells. ConclusionsEC-bound TM is released during stress-induced EC damage and becomes sTM, a paracrine factor that exerts anti-apoptotic activity. Our data indicate that sTM is not only an endothelial injury biomarker but also has cytoprotective effects on vascular endothelium.

Effects of the ginkgo biloba extract on the superoxide dismutase activity and apoptosis of endothelial progenitor cells from diabetic peripheral blood

Although ginkgo biloba extract (GBE) was shown to have antioxidant effects, little has been reported on the ability to GBE to help endothelial progenitor cells (EPCs) resist oxidative stress. The present study evaluated the influence of different concentrations of GBE on superoxide dismutase (SOD) and apoptosis of diabetic peripheral blood EPCs. Twenty-five diabetic patients without any vascular complications were included in the experimental group, while 15 healthy adults made up the control group. Peripheral blood mononuclear cells were isolated with density gradient centrifugation, and, after in vitro differentiation, were determined to be EPCs using FITC-UEA-I and Dil-Ac-LDL dual staining. After the colony and fusiform adherent cells were observed, on day 7, various concentrations of ginkgo biloba extract (0, 10, 25, 50 mg/L) were added to the culture medium for a 24-h incubation. EPC-SOD activity and apoptosis were subsequently detected. We found that within the experimental group, GBE significantly improved SOD activity within EPCs and reduced the rate of apoptosis. These effects became more obvious with increasing GBE concentrations (25 mg/L, P < 0.05; 50 mg/L, P < 0.01). GBE also improved SOD activity and reduced the rate of apoptosis within EPCs of the control group; however, the changes were not statistically significant. We conclude that GBE can improve SOD activity and reduce the rate of apoptosis of EPCs within the peripheral blood of diabetic patients, effects that are dose-dependent.

Effects of lycopene on number and function of human peripheral blood endothelial progenitor cells cultivated with high glucose.

BACKGROUND/OBJECTIVESThe objectives of this study were to investigate the effects of lycopene on the migration, adhesion, tube formation capacity, and p38 mitogen-activated protein kinase (p38 MAPK) activity of endothelial progenitor cells (EPCs) cultivated with high glucose (HG) and as well as explore the mechanism behind the protective effects of lycopene on peripheral blood EPCs.MATERIALS/METHODSMononuclear cells were isolated from human peripheral blood by Ficoll density gradient centrifugation. EPCs were identified after induction of cellular differentiation. Third generation EPCs were incubated with HG (33 mmol/L) or 10, 30, and 50 µg/mL of lycopene plus HG. MTT assay and flow cytometry were performed to assess proliferation and apoptosis of EPCs. EPC migration was assessed by MTT assay with a modified boyden chamber. Adhesion assay was performed by replating EPCs on fibronectin-coated dishes, after which adherent cells were counted. In vitro vasculogenesis activity was assayed by Madrigal network formation assay. Western blotting was performed to analyze protein expression of both phosphorylated and non-phosphorylated p38 MAPK.RESULTSThe proliferation, migration, adhesion, and in vitro vasculogenesis capacity of EPCs treated with 10, 30, and 50 µg/mL of lycopene plus HG were all significantly higher comapred to the HG group (P < 0.05). Rates of apoptosis were also significantly lower than that of the HG group. Moreover, lycopene blocked phosphorylation of p38 MAPK in EPCs (P < 0.05). To confirm the causal relationship between MAPK inhibition and the protective effects of lycopene against HG-induced cellular injury, we treated cells with SB203580, a phosphorylation inhibitor. The inhibitor significantly inhibited HG-induced EPC injury.CONCLUSIONSLycopene promotes proliferation, migration, adhesion, and in vitro vasculogenesis capacity as well as reduces apoptosis of EPCs. Further, the underlying molecular mechanism of the protective effects of lycopene against HG-induced EPC injury may involve the p38 MAPK signal transduction pathway. Specifically, lycopene was shown to inhibit HG-induced EPC injury by inhibiting p38 MAPKs.

Obstructive sleep apnea and endothelial progenitor cells

BackgroundObstructive sleep apnea (OSA) occurs in 4% of middle-aged men and 2% of middle-aged women in the general population, and the prevalence is even higher in specific patient groups. OSA is an independent risk factor for a variety of cardiovascular diseases. Endothelial injury could be the pivotal determinant in the development of cardiovascular pathology in OSA. Endothelial damage ultimately represents a dynamic balance between the magnitude of injury and the capacity for repair. Bone marrow–derived endothelial progenitor cells (EPCs) within adult peripheral blood present a possible means of vascular maintenance that could home to sites of injury and restore endothelial integrity and normal function.MethodsWe summarized pathogenetic mechanisms of OSA and searched for available studies on numbers and functions of EPCs in patients with OSA to explore the potential links between the numbers and functions of EPCs and OSA. In particular, we tried to elucidate the molecular mechanisms of the effects of OSA on EPCs.ConclusionIntermittent hypoxia cycles and sleep fragmentation are major pathophysiologic characters of OSA. Intermittent hypoxia acts as a trigger of oxidative stress, systemic inflammation, and sympathetic activation. Sleep fragmentation is associated with a burst of sympathetic activation and systemic inflammation. In most studies, a reduction in circulating EPCs has emerged. The possible mechanisms underlying the decrease in the number or function of EPCs include prolonged inflammation response, oxidative stress, increased sympathetic activation, physiological adaptive responses of tissue to hypoxia, reduced EPC mobilization, EPC apoptosis, and functional impairment in untreated OSA. Continuous positive airway pressure (CPAP) therapy for OSA affects the mobilization, apoptosis, and function of EPCs through preventing intermittent hypoxia episodes, improving sleep quality, and reducing systemic inflammation, oxidative stress levels, and sympathetic overactivation. To improve CPAP adherence, the medical staff should pay attention to making the titration trial a comfortable first CPAP experience for the patients; for example, using the most appropriate ventilators or proper humidification. It is also important to give the patients education and support about CPAP use in the follow-up, especially in the early stage of the treatment.

Hydrogen peroxide induced impairment of endothelial progenitor cell viability is mediated through a FoxO3a dependant mechanism

ObjectivesIncreased oxidative stress has been suggested to contribute to the functional impairment of endothelial progenitor cells (EPCs). The Forkhead box O transcription factors (FoxOs) are critical regulators involved in various cellular processes including cell apoptosis. Here, we investigated whether FoxOs are required in oxidative stress induced EPC apoptosis. Methods and resultsEPCs were cultured from cord blood derived mononuclear cells and treated with hydrogen peroxide (H2O2) for induction of oxidative stress. Incubation with H2O2 dose dependently reduced viability and increased apoptosis in EPCs. Western blotting showed that EPCs predominantly expressed FoxO3a and the expression was markedly increased upon H2O2 treatment. Transduction with adenoviral vectors expressing either a wide-type or a non-phosphorylatable, constitutively active mutant of FoxO3a led to further increased apoptosis of EPCs after H2O2 treatment. Conversely, FoxO3a silencing rescued EPCs from these H2O2 induced deleterious effects. Overexpression of FoxO3a also increased the level of the pro-apoptotic protein Bim, whereas FoxO3a silencing downregulated H2O2 induced Bim expression. Furthermore, Matrigel assay demonstrated that FoxO3a overexpression significantly impaired the tube forming ability of EPCs, whereas its silencing completely protected EPCs from H2O2 induced decrease of capillary formation. ConclusionsThese data suggest that oxidative stress induced impairment of EPC survival is mediated through a FoxO3a dependant mechanism, possibly by transcriptional regulation of Bim. Our data indicate FoxO3a as a potential therapeutic target for improvement of EPC number and function in patients with ischemic heart disease.

The dual PPAR-alpha/gamma agonist aleglitazar increases number and function of endothelial progenitor cells: implications for vascular function and atherogenesis

Background: Endothelial progenitor cells (EPC) improve endothelial function and promote vascular repair. Aleglitazar combines lipid-modifying effects of PPAR-α agonists (fibrates) and insulin-sensitizing effects of PPAR-γ agonists (thiazolidinediones). We studied the effects of the novel dual peroxisome proliferator-activated receptor (PPAR)-α/γ agonist aleglitazar on glucose tolerance, EPC, endothelial function, neoangiogenesis and atherosclerosis in mice. Methods and results: C57Bl/6 wild-type (WT, normal chow), ApoE-/- mice (Western-type diet) and eNOS-/- mice were treated with aleglitazar (10 mg/kg/d, i.p.) or vehicle. Aleglitazar enhanced the expression of both the PPAR-α and PPAR-γ target genes and normalized glucose tolerance in cholesterol-fed ApoE-/- mice. In WT mice, aleglitazar treatment upregulated sca-1/VEGFR-2-positive EPC in the blood (153±10%) and bone marrow (197±22%), and upregulated spleen-derived diLDL/lectin-positive EPC (182±8%). Furthermore, aleglitazar augmented EPC migration (186±6% vs. controls) and enhanced neoangiogenesis (vascularized disk area 178±18% vs. controls). The effects of the dual PPAR-α/γ agonist on EPC number and function were abolished in eNOS knock-out mice. In ApoE-/- mice, aleglitazar upregulated EPC number and function, potently improved endothelium-dependent vasodilation and markedly reduced the formation of atherosclerotic plaques (plaque area/total lumen area 2.3±0.8% vs. 10.1±1.9% after 6 weeks and 22±2.2% vs. 36±2.1% after 8 weeks treatment). OilRed staining of hepatic sections showed a profound reduction of liver steatosis in ApoE-/- mice. In cultured human EPC, aleglitazar increased migration and colony forming units in a concentration-dependent manner. Furthermore, oxidative stress-induced EPC apoptosis and protein expression of p53 were reduced, while telomerase activity and expression of phospho-eNOS (S1177) and phospho-Akt were elevated. Comparative and inhibitor experiments revealed that aleglitazar's effects on EPC migration and colony forming units (CFU) were mediated by both PPAR-α and -γ signaling. E.g., aleglitazar treatment (10nM/l) induced EPC migration (304±21% vs. controls) and CFU (300±67% vs. controls) comparably to a co-stimulation of EPC with pioglitazone 10μM/l+fenofibric acid (150μM/l) (Migration: 332±28%; CFU: 289±72%). Conclusions: The dual PPAR-α/γ agonist aleglitazar augments number, function and survival of endothelial progenitor cells in an Akt- and eNOS-dependent fashion. The effects on EPC correlate with improved neoangiogenesis, restored endothelial function and prevention of atherosclerosis.

Osteoprotegerin Causes Apoptosis of Endothelial Progenitor Cells by Induction of Oxidative Stress

Elevated serum osteoprotegerin (OPG) levels represent an independent risk factor for atherosclerotic disease, although the underlying mechanism is not clear. The aim of this study was to investigate the association of serum OPG levels and circulating endothelial progenitor cell (EPC) numbers, and to explore the effect of OPG on EPC apoptosis and its underlying mechanisms. Flow cytometry was used to enumerate EPCs in the peripheral blood of 91 patients with systemic lupus erythematosus (SLE). Cultured EPCs, isolated from peripheral blood, were challenged with OPG, and apoptosis was evaluated by TUNEL staining. Expression of apoptosis-related proteins was measured by real-time quantitative polymerase chain reaction (qPCR) and Western blotting. Reactive oxygen species (ROS) were detected by flow cytometry, and the expression of NADPH oxidase (NOX) and MAP kinases (MAPK) was measured by qPCR and Western blotting. The serum OPG level was independently associated with reduced numbers of EPCs in patients with SLE. In vitro treatment with OPG significantly induced apoptosis of EPCs; this effect was mediated by syndecan 4. OPG-induced apoptosis was abolished by the ROS scavenger N-acetylcysteine and the NOX inhibitor diphenyleniodonium. OPG increased ROS production through activation of NOX-2 and NOX-4 and triggered phosphorylation of ERK-1/2 and p38 MAPK. Quenching of ROS by knockdown of NOX-2 or NOX-4 transcripts inhibited phosphorylation of ERK-1/2 and p38 MAPK. Moreover, inhibitors of ERK-1/2 and p38 MAPK decreased ROS production and subsequent EPC apoptosis, indicating a feed-forward loop between NOX and MAPK to amplify ROS production related to apoptosis. Elevated OPG levels increase apoptosis of EPCs by induction of oxidative stress.

ClC-3 deficiency prevents apoptosis induced by angiotensin II in endothelial progenitor cells via inhibition of NADPH oxidase

Endothelial progenitor cells (EPCs) play an important role in postnatal neovascularization and re-endothelialization in response to tissue ischemia and endothelial injury. It is reported that the circulating EPCs number is decreased during hypertension. However, the detailed mechanism is still unclear. Our previous studies have shown that ClC-3 chloride channel is up-regulated with the development of hypertension. This study aims to test whether ClC-3 participates in EPC apoptosis under the condition of increased oxidative stress in angiotensin II (Ang II)-induced hypertension. The results showed that stimulation with 10(-6)mol/L Ang II significantly up-regulated the endogenous ClC-3 expression and increased intracellular reactive oxygen species (ROS) generation in EPCs of wild type mice, accompanied by an enhanced NADPH oxidase activity and the expression of gp91(phox) (NOX-2), a key catalytic subunit of NADPH oxidase. However, these effects of Ang II were significantly reduced in EPCs of ClC-3(-/-) mice. Compared with control, treatment with Ang II induced EPCs apoptosis in wild type mice, concomitantly with declined Bcl-2/Bax ratio, depressed mitochondrial membrane potential and activation of poly(ADP-ribose) polymerase, which was remarkably prevented by both ClC-3 knockout and NADPH oxidase inhibitor apocynin. In addition, the role of ClC-3 deficiency in protecting EPCs against Ang II-induced oxidative stress and apoptosis was further confirmed in Ang II-infused hypertensive mice in vivo. In conclusion, ClC-3 deficiency inhibited Ang II-induced EPC apoptosis via suppressing ROS generation derived from NADPH oxidase.

In vitro interactions between rat bone marrow-derived endothelial progenitor cells and hepatic stellate cells

Transplantation of bone marrow (BM)-derived endothelial progenitor cells (EPCs) has been reported to improve liver fibrosis, but there is no direct evidence for the mechanism of improvement. We investigated the mechanism in vitro by coculturing BM-derived EPCs with activated hepatic stellate cells (HSCs) to mimic the hepatic environment. EPCs and HSCs were cultured alone and indirectly cocultured at a 1:1 ratio in a Transwell system. The characteristics of HSCs and EPCs were examined at different time points. An invasion assay showed the time-dependent effect on degradation of the extracellular matrix (ECM) layer in EPCs cultured alone. Real-time PCR and enzyme-linked immunosorbent assay analysis revealed that EPCs served as a source of matrix metalloproteinase-9 (MMP-9), and MMP-9 expression levels significantly increased during the 2d of coculture. CFSE labeling showed that EPCs inhibited proliferation of HSCs. Annexin-V/PI staining, erminal deoxynucleotidyl transferase X-dUTP nick end labeling analysis, and (cleaved) caspase-3 activity revealed that EPCs promoted HSC apoptosis. However, the proliferation and apoptosis of EPCs were unaffected by cocultured HSCs. Coculturing increased the expression of inducible nitric oxide synthase, vascular endothelial growth factor, and hepatocyte growth factor (HGF) in EPCs, promoted differentiation of EPCs, and reduced the expression of types I and III collagens and transforming growth factor beta 1. Knockdown of HGF expression attenuated EPC-induced activation of HSC apoptosis and profibrotic ability. These findings demonstrated that BM-derived EPCs could degrade ECM, promoting activated HSC apoptosis, suppressing proliferation and profibrotic ability of activated HSCs. HGF secretion by EPCs plays a key role in inducing activated HSC apoptosis and HSC profibrotic ability.

Cytoprotective effect of dieckol on human endothelial progenitor cells (hEPCs) from oxidative stress-induced apoptosis

Although endothelial progenitor cells (EPCs) have been used to promote revascularization after peripheral or myocardial ischemia, excess amounts of reactive oxygen species (ROS) are often involved in senescence and apoptosis of EPCs, thereby causing defective neovascularization and reduced or failed recovery. Here, we examined the cytoprotective effect of Ecklonia cava-derived antioxidant dieckol (DK) on oxidative stress-induced apoptosis in EPCs to improve EPC bioactivity for vessel repair. Although H2O2 (10 − 3 M) increased the intracellular ROS level in EPCs, DK (10ug/ml) pretreatment suppressed the H2O2-induced ROS increase and drastically reduced the ratios of apoptotic cells. H2O2-induced ROS increased the phosphorylation of p38 MAPK and JNK; this was inhibited by DK pretreatment. H2O2 treatment increased the phosphorylation of NF-κB, which was blocked by pretreatment with SB 203580, a p38 MAPK inhibitor, or SP 600125, a JNK inhibitor. H2O2 decreased the cellular levels of Bcl-2 and c-IAPs, cellular inhibitors of apoptosis proteins, but increased caspase-3 activation. However, all these effects were inhibited by pretreatment with DK. Injection of DK-mixed EPCs (DK + EPCs) into myocardial ischemic sites in vivo induced cellular proliferation and survival of cells at the ischemic sites and, thereby, enhanced the secretion of angiogenic cytokines at the ischemic sites. These results show that DK + EPC exhibit markedly enhanced anti-apoptotic and antioxidative capabilities, unlike that shown by EPCs alone; thus, they contribute to improved repair of ischemic myocardial injury through cell survival and angiogenic cytokine production.

Diesel Exhaust Particles Impair Endothelial Progenitor Cells, Compromise Endothelial Integrity, Reduce Neoangiogenesis, and Increase Atherogenesis in Mice

The mechanisms of the harmful cardiovascular effects of small particulate matter are incompletely understood. Endothelial progenitor cells (EPCs) predict outcome of patients with vascular disease. The aim of our study was to examine the effects of diesel exhaust particles (DEP) on EPC and on the associated vascular damage in mice. C57Bl/6 mice were exposed to DEP. 2 μg DEP/day was applicated intranasally for 3 weeks. Exposure to DEP reduced DiLDL/lectin positive EPC to 58.4 ± 5.6% (p < 0.005). Migratory capacity was reduced to 65.8 ± 3.9% (p < 0.0001). In ApoE(-/-) mice, DEP application reduced the number of EPC to 75.6 ± 6.4% (p < 0.005) and EPC migration to 58.5 ± 6.8% (p < 0.005). Neoangiogenesis was reduced to 39.5 ± 14.6% (p < 0.005). Atherogenesis was profoundly increased by DEP treatment (157.7 ± 18.1% vs. controls, p < 0.05). In cultured human EPC, DEP (0.1-100 μg/mL) reduced migratory capacity to 25 ± 2.6% (p < 0.001). The number of colony-forming units was reduced to 8.8 ± 0.9% (p < 0.001) and production of reactive oxygen species was elevated by DEP treatment (p < 0.001). Furthermore, DEP treatment increased apoptosis of EPC (to 266 ± 62% of control, p < 0.05). In a blood-brain barrier model, DEP treatment impaired endothelial cell integrity during oxygen-glucose deprivation (p < 0.001). Diesel exhaust particles impair endothelial progenitor cell number and function in vivo and in vitro. The reduction in EPC was associated with impaired neoangiogenesis and a marked increase in atherosclerotic lesion formation.

PPAR‐γ agonist pioglitazone prevents apoptosis of endothelial progenitor cells from rat bone marrow

Selective peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist affects the functions of endothelial progenitor cells (EPCs). This study explores the effect of selective PPAR-γ agonist, pioglitazone, on EPC apoptosis. The cells were cultured and identified via the double staining method in a medium containing different concentrations of pioglitazone. EPC apoptosis was detected by flow cytometry. On Day 7, EPCs engulfed DiL-ac-LDL and FITC-UEA-1, and showed yellow fluorescence in a laser-scanning confocal microscope. EPC apoptosis inhibition was maximal at 50 µmol/L. The ability of pioglitazone to prevent EPC apoptosis may be mediated by the PI3K/Akt signal pathway. The use of thiazolidine two ketone (TZD) to reduce EPC apoptosis may have some potential in treating vascular diseases.

Impaired cross-activation of β3 integrin and VEGFR-2 on endothelial progenitor cells with aging decreases angiogenesis in response to hypoxia

The mechanism by which vascular regeneration declines with aging is not fully understood. An interaction between integrin and vascular endothelial growth factor receptor-2 (VEGFR-2) plays a substantial role in angiogenesis. Here, we investigated whether aging impairs this interaction in endothelial progenitor cells (EPCs) under hypoxia. Aging reduced the blood flow and vessel density in ischemic muscles in mice. Levels of phosphorylated Src (p-Src), p-β3, and p-VEGFR-2 in acute ischemia were reduced in the muscles of aged mice compared to young mice. The hypoxia-inducible factor (HIF)-1α stabilizer deferoxamine improved the age-related impairment of angiogenesis, but this effect was diminished by LY290004, an inhibitor of phosphatidylinositol 3-kinase. Deferoxamine improved the reduction in chronic ischemia-induced β3-integrin and VEGFR-2 phosphorylation in the muscles of aged mice; this effect was also diminished by LY290004. In EPCs, we identified the molecular requirements for VEGF-mediated β3-integrin and VEGFR-2 cross-activation in vitronectin-induced cell adhesion under acute hypoxia. We demonstrated that c-Src controlled the adhesion- and VEGF-induced β3 tyrosine phosphorylation in hypoxia. Aging enhanced the hypoxia-induced EPC apoptosis and impaired several c-Src-related VEGF-induced receptor events, including β3 tyrosine activation, ligand binding, cell adhesion, and tubulogenesis in cultured EPCs of animals and those of humans. These data suggest that the aging-related decline in angiogenic action in response to ischemia is mediated by the impairment of cross-activation between β3 and VEGFR-2 in EPCs, which is partially associated with decreased HIF-1α stability.

Caspase-3 expression and cell morphology of early endothelial progenitor cells exposed to N-epsilon-carboxymethyl lysine

The role of endothelial progenitor cells (EPCs) on vascular repair and neovasculogenesis is impaired in diabetes. This study aimed to investigate the effect of N-epsilon-carboxymethyl lysine (CML) on caspase-3 expression and morphology of early EPCs. After 7 days of culturing, primary cultures of early EPCs were randomly divided into four groups. One group is a normal group. Three groups were exposed to low (50 µg/ml), medium (100 µg/ml), and high (200 µg/ml) doses of CML for an hour. The caspase-3 expression and morphology of early EPCs were evaluated by laser scanning confocal microscope. The caspase-3 expression of early EPCs increased in groups exposed to low and medium dose of CML, and decreased in group exposed to high dose of CML compared to normal. Exposure of CML changed the morphology of early EPCs including cells shrinkage, unclear margin between cytoplasm and nucleus, also oval-shape cells. Given that CML may contribute to the functional defects of the endothelium in diabetes by causing early EPCs apoptosis via increased caspase-3 expression.

Autophagy in endothelial progenitor cells is cytoprotective in hypoxic conditions

Endothelial progenitor cells (EPCs) may be incorporated into local vessels to enhance angiogenesis within ischemic tissue. Recently, EPC transplantation has become a potential therapy for improving tissue function in cardiovascular disease. However, the mechanisms of proliferation, differentiation, and survival of EPCs in a hypoxic microenvironment remain unclear. In this study, CD34(+)VEGFR-2(+) EPCs were isolated from mononuclear cells of human umbilical cord blood, and differentiation to endothelial cells was induced with VEGF. When EPC autophagy was inhibited with 3-methyladenine (3-MA) under normoxic conditions, proliferation and viability of the cells were decreased, and the cells failed to differentiate into endothelial cells. Under hypoxic conditions (1% O(2)), Beclin-1 expression of the cells was upregulated and both MDC-labeled and LC3-positive puncta and autophagic ultrastructures in the cells increased significantly. The number of lysosomes also increased in hypoxia-exposed cells. When autophagy was inhibited with 3-MA under hypoxic conditions, the number of apoptotic cells increased, and the number and size of lysosomes decreased. Conversely, apoptosis of the hypoxic EPCs was reduced when autophagy was induced by pretreatment with rapamycin. These results demonstrate that autophagy is involved in proliferation and differentiation of EPCs. Furthermore, hypoxia activates autophagy, promoting EPC survival by inhibiting apoptosis. Enhancing autophagy with hypoxic preconditioning may be beneficial for survival of the transplanted EPCs in a local hypoxic environment.

Actin Stabilization by Jasplakinolide Affects the Function of Bone Marrow-Derived Late Endothelial Progenitor Cells

BackgroundBone marrow-derived endothelial progenitor cells (EPCs), especially late EPCs, play a critical role in endothelial maintenance and repair, and postnatal vasculogenesis. Although the actin cytoskeleton has been considered as a modulator that controls the function and modulation of stem cells, its role in the function of EPCs, and in particular late EPCs, remains poorly understood.Methodology/Principal FindingBone marrow-derived late EPCs were treated with jasplakinolide, a compound that stabilizes actin filaments. Cell apoptosis, proliferation, adhesion, migration, tube formation, nitric oxide (NO) production and endothelial NO synthase (eNOS) phosphorylation were subsequently assayed in vitro. Moreover, EPCs were locally infused into freshly balloon-injured carotid arteries, and the reendothelialization capacity was evaluated after 14 days. Jasplakinolide affected the actin distribution of late EPCs in a concentration and time dependent manner, and a moderate concentration of (100 nmol/l) jasplakinolide directly stabilized the actin filament of late EPCs. Actin stabilization by jasplakinolide enhanced the late EPC apoptosis induced by VEGF deprivation, and significantly impaired late EPC proliferation, adhesion, migration and tube formation. Furthermore, jasplakinolide attenuated the reendothelialization capacity of transplanted EPCs in the injured arterial segment in vivo. However, eNOS phosphorylation and NO production were increased in late EPCs treated with jasplakinolide. NO donor sodium nitroprusside (SNP) rescued the functional activities of jasplakinolide-stressed late EPCs while the endothelial NO synthase inhibitor L-NAME led to a further dysfunction induced by jasplakinolide in late EPCs.Conclusions/SignificanceA moderate concentration of jasplakinolide results in an accumulation of actin filaments, enhancing the apoptosis induced by cytokine deprivation, and impairing the proliferation and function of late EPCs both in vitro and in vivo. NO donor reverses these impairments, suggesting the role of NO-related mechanisms in jasplakinolide-induced EPC downregulation. Actin cytoskeleton may thus play a pivotal role in regulating late EPC function.

Transfusion of CXCR4-Primed Endothelial Progenitor Cells Reduces Cerebral Ischemic Damage and Promotes Repair in db/db Diabetic Mice

This study investigated the role of stromal cell-derived factor-1α (SDF-1α)/CXC chemokine receptor 4 (CXCR4) axis in brain and endothelial progenitor cells (EPCs), and explored the efficacy of CXCR4 primed EPCs in treating ischemic stroke in diabetes. The db/db diabetic and db/+ mice were used in this study. Levels of plasma SDF-1α and circulating CD34+CXCR4+ cells were measured. Brain SDF-1α and CXCR4 expression were quantified at basal and after middle cerebral artery occlusion (MCAO). In in vitro study, EPCs were transfected with adenovirus carrying null (Ad-null) or CXCR4 (Ad-CXCR4) followed with high glucose (HG) treatment for 4 days. For pathway block experiments, cells were pre-incubated with PI3K inhibitor or nitric oxide synthase (NOS) inhibitor for two hours. The CXCR4 expression, function and apoptosis of EPCs were determined. The p-Akt/Akt and p-eNOS/eNOS expression in EPCs were also measured. In in vivo study, EPCs transfected with Ad-null or Ad-CXCR4 were infused into mice via tail vein. On day 2 and 7, the cerebral blood flow, neurologic deficit score, infarct volume, cerebral microvascular density, angiogenesis and neurogenesis were determined. We found: 1) The levels of plasma SDF-1α and circulating CD34+CXCR4+ cells were decreased in db/db mice; 2) The basal level of SDF-1α and MCAO-induced up-regulation of SDF-1α/CXCR4 axis were reduced in the brain of db/db mice; 3) Ad-CXCR4 transfection increased CXCR4 expression in EPCs and enhanced EPC colonic forming capacity; 4) Ad-CXCR4 transfection prevented EPCs from HG-induced dysfunction (migration and tube formation) and apoptosis via activation of PI3K/Akt/eNOS signal pathway; 4) Ad-CXCR4 transfection enhanced the efficacy of EPC infusion in attenuating infarct volume and promoting angiogenesis and neurogenesis. Our data suggest that Ad-CXCR4 primed EPCs have better therapeutic effects for ischemia stroke in diabetes than unmodified EPCs do.

Abstract 19517: Pro-Angiogenic MicroRNA-27b Retards EPC Apoptosis and Accelerates Wound Healing in Type 2 Diabetes via Suppressing p53 and Bax/Bcl-2 Ratio

Introduction: Endothelial progenitor cells (EPCs) are promising candidates for autologous cell therapy of diabetic wound repair because of their high angiogenic potentials. However, increased EPC apoptosis in diabetes directly limits its clinical success. MicroRNAs are endogenous non-coding RNAs that regulate gene expression at the post-transcriptional level, but their roles in EPC-mediated angiogenesis in diabetes are incompletely understood. We hypothesized that the pro-angiogenic miR-27b inhibits EPC apoptosis and improves wound healing in type 2 diabetes. Methods and Results: Bone marrow-derived EPCs from adult male type 2 diabetic db/db mice and their normal littermates db/+ mice were used. MiR-27b expression (real-time PCR) in EPCs was decreased by &gt;66% in db/db vs. db/+ mice (n=4, p&lt;0.05). The impaired EPC angiogenesis of &gt;70% (Matrigel tube formation, n=4, vs. db/+) and increased EPC apoptosis (TUNEL staining, n=3, p&lt;0.05 vs. db/+) in diabetes were rescued following miR-27b mimic transfection (n=3, p&lt;0.05 vs. db/db + scramble). p53 and Bax/Bcl-2 ratio in EPCs (Western blot analyses) were significantly higher in db/db mice (by 23% and 58%, respectively, vs. db/+), which were suppressed by miR-27b mimic (n=3, p&lt;0.05 vs. db/db + scramble). Excisional wound (6-mm diameter) closure was markedly delayed in db/db vs. db/+ mice (n=5, p&lt;0.05), accompanied by poorer wound angiogenesis (Laser Doppler detection, n=5, p&lt;0.05) and elevated expression of p53 (&gt; 72%) and Bax/Bcl-2 ratio (&gt; 55%) (both n=5 vs. db/+). Local delivery of miR-27b mimic or cell therapy using diabetic EPCs (10 6 ) with miR-27b mimic transfection significantly accelerated wound closure rates (n=5, p&lt;0.05), with a concomitant augmentation of wound perfusion in db/db mice (n=5, p&lt;0.05). Conclusion: miR-27b retards EPC apoptosis and accelerates wound healing in type 2 diabetic mice, at least in part, via suppressing p53 and Bax/Bcl-2 ratio. These findings may provide a mechanistic basis for rescuing EPC dysfunction in diabetes for successful autologous cell therapy.

Endothelial progenitor cells in relation to endothelin-1 and endothelin receptor blockade: A randomized, controlled trial

Endothelial progenitor cells (EPC) represent an endogenous repair mechanism involving rendothelialization and neoangiogenesis. Patients with both diabetes and vascular disease have low numbers of circulating EPC. The endothelium-derived peptide, endothelin-1 (ET-1), is increased in patients with type 2 diabetes and vascular complications and has been suggested to contribute to endothelial dysfunction. Therefore, we investigated the relation between EPC and plasma ET-1 and the effect of dual ET-1 receptor antagonist treatment. In this double blind study patients with type 2 diabetes mellitus and microalbuminuria were randomized to treatment with the dual ETA/ETB receptor antagonist bosentan treatment (125mg bid; n=17) or placebo (n=19) for four weeks. Different EPC subpopulations were enumerated by flow cytometry using triple staining (CD34, CD133, KDR) at baseline at the end of treatment. Viability was assessed by 7AAD and Annexin-V-staining. Baseline ET-1 levels correlated significantly with C-reactive protein levels. Patients with ET-1 levels above the median value had higher levels of CD34(+)CD133(+) and CD34(+)KDR(+) EPC. There was no difference in CD34(+) and CD34(+)CD133(+)KDR(+) cells, markers of EPC apoptosis or circulating markers of endothelial damage between patients with ET-1 levels below or above the median. Four week treatment with bosentan did not change EPC levels. Among patients with type 2 diabetes and vascular disease, high plasma levels of ET-1 are associated with higher number of EPC. The recruitment of EPC does not seem to be regulated via ET-1 receptor activation since treatment with a dual ET-1 receptor blocker did not affect circulating EPC numbers.

Zoledronate Attenuates Angiogenic Effects of Angiotensin II-Stimulated Endothelial Progenitor Cells via RhoA and MAPK Signaling

BackgroundNew vessel formation plays a pivotal role in the pathogenesis of neovascular-related diseases. Endothelial progenitor cells (EPCs) were found to contribute to neovascular-related diseases and interference with EPC neovascularization may be a novel target for these diseases. Zoledronate (Zol) was reported to exhibit anti-angiogenic effect. Basing on these evidences, we proposed that Zol may affect EPC function to exert novel anti-angiogenic effect. In this study, we therefore investigated the effects of Zol on multiple aspects of EPC function and explored the underlying mechanisms involved.Methodology/Principal FindingsEPCs were cultured from bone marrow derived mononuclear cells. The potential effects of Zol on Angiotensin II (Ang II)-stimulated EPC proliferation, migration, adhesion, in vitro tube formation were investigated. The results showed that Ang II (1 µM) enhanced EPC migration, adhesion, in vitro tube formation but had no effect on cell proliferation. Zol (75 and 100 µM) inhibited proliferation of EPCs and 50 µM geranylgeranyol (GGOH) could reverse the decrease of EPC proliferation. We found for the first time that Zol (50–100 µM) dose dependently attenuated migration, adhesion, and in vitro tube formation of EPCs stimulated by Ang II. GGOH could reverse the attenuation of EPC function induced by Zol. However, Zol did not induce EPC apoptosis. In addition, the underlying mechanisms were determined. The results revealed that Zol markedly down-regulated active RhoA stimulated by Ang II and inhibited the phosphorylation of Erk1/2 and JNK. Moreover, RhoA silencing resulted in a notable inhibition of EPC in vitro tube formation, suggesting that RhoA suppression played a pivotal role in Zol antiangiogenic effect.Conclusions/SignificanceThese findings suggested that Zol attenuated the promotion of EPC function stimulated by Ang II and exhibited novel antiangiogenic effect via RhoA and MAPK signaling. Thus, Zol may be served as a novel therapeutic agent for neovascular-related diseases treatment.