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Bone marrow-derived endothelial progenitor cells (EPCs) contribute to endothelial repair and angiogenesis. Reduced number of circulating EPCs is associated with future cardiovascular events. We tested whether dysregulated glucose and/or triglyceride (TG) metabolism has an impact on EPC homeostasis. The analysis of metabolic factors associated with circulating EPC number in humans revealed that postprandial hyperglycemia is negatively correlated with circulating EPC number, and this correlation appears to be further enhanced in the presence of postprandial hypertriglyceridemia (hTG). We therefore examined the effect of glucose/TG spikes on bone marrow lineage-sca-1 + c-kit + (LSK) cells in mice, because primitive EPCs reside in bone marrow LSK fraction. Repetitive glucose + lipid (GL) spikes, but not glucose (G) or lipid (L) spikes alone, induced senescence-like phenotypes of LSK cells, and this phenomenon was reversible after cessation of GL spikes. G spikes and GL spikes differentially affected transcriptional program of LSK cell metabolism and differentiation. GL spikes upregulated a histone H3K27 demethylase JMJD3, and inhibition of JMJD3 eliminated GL spikes-induced LSK cell senescence-like phenotypes. These observations suggest that postprandial glucose/TG dysmetabolism modulate transcriptional regulation in LSK cells through H3K27 demethylase-mediated epigenetic regulation, leading to senescence-like phenotypes of LSK cells, reduced number of circulating EPCs, and development of atherosclerotic cardiovascular disease. NEW & NOTEWORTHY Combination of hyperglycemia and hypertriglyceridemia is associated with increased risk of atherosclerotic cardiovascular disease. We found that 1 ) hypertriglyceridemia may enhance the negative impact of hyperglycemia on circulating EPC number in humans and 2 ) metabolic stress induced by glucose + triglyceride spikes in mice results in senescence-like phenotypes of bone marrow stem/progenitor cells via H3K27me3 demethylase-mediated epigenetic regulation. These findings have important implications for understanding the pathogenesis of atherosclerotic cardiovascular disease in patients with T2DM.

Endothelial progenitor cell (EPC) transplantation has shown advantages in the treatment of myocardial infarction (MI) in animal models and clinical trials through mechanisms of direct intercellular contacts, autocrine, and paracrine. However, the effects of EPC transplantation for MI treatment remain controversial and the underlying mechanisms have not been fully elucidated. Here, we explored the role of Rab27a in the therapeutic potential of EPC transplantation in MI. We found that Rab27a knockout impaired the viability, and reduced the proliferation and tube formation function of ECPs. The recovery of cardiac function and improvement of ventricular remodeling from EPCs transplantation were significantly damaged by Rab27a deletion in vivo. Rab27a deletion inhibited the protein expression of phosphoinositide 3-kinase (PI3K) and cyclin D1 and the phosphorylation levels of Akt and FoxO3a. Therefore, Rab27a knockout suppressed the PI3K-Akt-FoxO3a/cyclin D1 signaling pathway. Furthermore, Rab27a ablation dramatically reduced exosome release in EPCs. These results demonstrated that Rab27a plays an essential role in EPC functions. The elucidation of this mechanism provides novel insights into EPC transplantation as a promising treatment for post-MI injuries.

Endothelial progenitor cells (EPCs) are important to tissue repair and regeneration especially after ischemic injury, and very heterogeneous in phenotypes and biological features. Reactive oxygen species are involved in regulating EPC number and function. N-acetylcysteine (NAC) inhibits ischemia-induced reactive oxygen species formation and promotes ischemic limb recovery. This study was to evaluate the effect of NAC on EPC subpopulations in bone marrow (BM) and blood in mice with limb ischemia. Limb ischemia was induced by femoral artery ligation in male C57BL/6 mice with or without NAC treatment. EPC subpopulations, intracellular reactive oxygen species production, cell proliferation and apoptosis in BM and blood cells were analyzed at baseline, day 3 (acute ischemia) and 21 (chronic) after ligation. c-Kit+/CD31+, Sca-1+/Flk-1+, CD34+/CD133+, and CD34+/Flk-1+ were used to define EPC subpopulations. Limb blood flow, function, muscle structure, and capillary density were evaluated with laser Doppler perfusion imaging, treadmill test, and immunohistochemistry, respectively, at day 3, 7, 14 and 21 post ischemia. Reactive oxygen species production in circulating and BM mononuclear cells and EPCs populations were significantly increased in BM and blood in mice with acute and chronic ischemia. NAC treatment effectively blocked ischemia-induced reactive oxygen species production in circulating and BM mononuclear cells, and selectively increased EPC population in circulation, not BM, with preserved proliferation in mice with chronic ischemia, and enhanced limb blood flow and function recovery, while preventing acute ischemia-induced increase in BM and circulating EPCs. These data demonstrated that NAC selectively enhanced circulating EPC population in mice with chronic limb ischemia., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Putative endothelial progenitor cells (pEPCs) have been confirmed to participate in alleviation of renal fibrosis in several ischaemic diseases. However, their mechanistic effect on renal fibrosis, which is characterized by vascular regression and further rarefaction-related pathology, remains unknown., Methods: To explore the effect and molecular mechanisms by which pEPCs act on unilateral ureteral obstruction (UUO)-induced renal fibrosis, we isolated pEPCs from murine bone marrow. In vivo, pEPCs (2 × 10 5 cells/day) and pEPC-MVs (microvesicles) were injected into UUO mice via the tail vein. In vitro, pEPCs were co-cultured with renal-derived pericytes. Pericyte-myofibroblast transition was evaluated using the myofibroblast marker α-smooth muscle actin (α-SMA) and pericyte marker platelet-derived growth factor receptor β (PDGFR-β)., Results: Exogenous supply of bone marrow-derived pEPCs attenuated renal fibrosis by decreasing pericyte-myofibroblast transition without significant vascular repair in the UUO model. Our results indicated that pEPCs regulated pericytes and their transition into myofibroblasts via pEPC-MVs. Co-culture of pericytes with pEPCs in vitro suggested that pEPCs inhibit transforming growth factor-β (TGF-β)-induced pericyte-myofibroblast transition via a paracrine pathway., Conclusion: pEPCs effectively attenuated UUO-induced renal fibrosis by inhibiting pericyte-myofibroblast transition via a paracrine pathway, without promoting vascular repair.

Purpose: This study aimed to explore whether bone marrow- (BM-) derived endothelial progenitor cells (EPCs) contributing to monocrotaline- (MCT-) induced pulmonary arterial hypertension (PAH) in rats via modulating store-operated Ca 2+ channels (SOC)., Methods: Sprague Dawley (SD) rats were assigned into MCT group (n = 30) and control group (n = 20). Rats in MCT group were subcutaneously administered with 60 mg/kg MCT solution, and rats in control group were injected with equal amount of vehicle. After 3 weeks of treatment, right ventricular systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI) of two groups were measured, and BM-derived EPCs were isolated. Immunochemistry identification and vasculogenesis detection of EPCs were then performed. [Ca 2+ ] cyt measurement was performed to detect store-operated calcium entry (SOCE) in two groups, followed by determination of Orai and canonical transient receptor potential (TRPC) channels expression., Results: After 3 weeks of treatment, there were significant increases in RVSP and RVHI in MCT group compared with control group, indicating that MCT successfully induced PAH in rats. Moreover, the SOCE ([Ca 2+ ] cyt rise) in BM-derived EPCs of MCT group was lower than that of control group. Furthermore, the expression levels of Orai3, TRPC1, TRPC3, and TRPC6 in BM-derived EPCs were decreased in MCT group in comparison with control group., Conclusions: The SOC activities were inhibited in BM-derived EPCs of MCT-treated rats. These results may be associated with the depressed expression of Orai3, TRPC1, TRPC3, and TRPC6, which are major mediators of SOC.

Graft-versus-host disease (GVHD) is a major complication after allogeneic haematopoietic stem cell transplantation (allo-HSCT) that is frequently associated with bone marrow (BM) suppression, and clinical management is challenging. BM endothelial progenitor cells (EPCs) play crucial roles in the regulation of haematopoiesis and thrombopoiesis. However, little is known regarding the functional roles of BM EPCs in acute GVHD (aGVHD) patients. In the current prospective case-control study, reduced and dysfunctional BM EPCs, characterized by decreased migration and angiogenesis capacities and increased levels of reactive oxygen species (ROS) and apoptosis, were found in aGVHD patients compared with those without aGVHD. Moreover, lower frequency and increased levels of ROS, apoptosis and DNA damage, but reduced colony-forming unit-plating efficiency were found in BM CD34 + cells of aGVHD patients compared with those without aGVHD. The severity of aGVHD and GVHD-mediated cytopenia was associated with BM EPC impairment in aGVHD patients. In addition, the EPC impairment positively correlated with ROS level. Taken together, our results suggest that reduced and dysfunctional BM EPCs may be involved in the pathogenesis of aGVHD. Although these findings require validation, our data indicate that improvement of BM EPCs may represent a promising therapeutic approach for aGVHD patients., (© 2018 British Society for Haematology and John Wiley & Sons Ltd.)

Objective: Considering the poor efficacy of local intramuscular injections with endothelial progenitor cells (EPCs) for critical limb ischemia in patients with diabetes, the study aimed to investigate the effect of α-tocopherol (α-T) and α-tocopherol phosphate (α-TP) on apoptosis and angiogenesis in a rat model under oxidative stress conditions., Methods: Primary EPCs from Sprague-Dawley rats were harvested and treated with α-T and α-TP for 24 hours. Gene transcription and protein expression were evaluated by real-time polymerase chain reaction and Western blot, respectively. Cell apoptosis, migration, and tube formation ability were detected by flow cytometry, Transwell assay (Chemicon International, Temecula, Calif), and Matrigel-based angiogenesis assay (Corning Inc, Corning, NY). The in vivo experiments were carried out using 30 single hind limb ischemic models of diabetic rats that were treated with allogeneic EPCs. Capillary density was evaluated by immunohistochemistry., Results: α-T and α-TP attenuated high glucose/hypoxia-induced cell apoptosis by promoting Bcl-2 and Akt and inhibiting nuclear factor κB p65, JNK, Notch-1, and p38MAPK genes. Furthermore, α-T and α-TP promoted the transcription and expression of vascular endothelial growth factor receptor 2 and decreased the transcription and expression of Tie-2 and Notch-1 in EPCs under high-glucose/hypoxic conditions. Moreover, α-T and especially α-TP enhanced the migratory activity of EPCs under high-glucose/hypoxic conditions. Capillary density of ischemic hind limbs was increased on day 14 after administration of EPCs pretreated with α-T and α-TP., Conclusions: α-T, especially α-TP, possesses therapeutic potential in the inhibition of apoptosis and increases the migratory capacity of EPCs under high-glucose/hypoxic conditions. It promotes angiogenesis by upregulating Bcl-2, Akt, and vascular endothelial growth factor receptor 2 and decreasing nuclear factor κB p65, p38MAPK, Notch-1, JNK, and Tie-2., (Copyright © 2017 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Objective: Lineage-negative bone marrow cells (lin- BMCs) are enriched in endothelial progenitor cells and mediate vascular repair. Aging-associated senescence and apoptosis result in reduced number and functionality of lin- BMCs, impairing their prorepair capacity. The molecular mechanisms underlying lin- BMC senescence and apoptosis are poorly understood. MicroRNAs (miRNAs) regulate many important biological processes. The identification of miRNA-mRNA networks that modulate the health and functionality of lin- BMCs is a critical step in understanding the process of vascular repair. The aim of this study was to characterize the role of the miR-146a-Polo-like kinase 2 (Plk2) network in regulating lin- BMC senescence, apoptosis, and their angiogenic capability., Approach and Results: Transcriptome analysis in lin- BMCs isolated from young and aged wild-type and ApoE -/- (apolipoprotein E) mice showed a significant age-associated increase in miR-146a expression. In silico analysis, expression study and Luciferase reporter assay established Plk2 as a direct target of miR-146a. miR-146a overexpression in young lin- BMCs inhibited Plk2 expression, resulting in increased senescence and apoptosis, via p16Ink4a/p19Arf and p53, respectively, as well as impaired angiogenic capacity in vitro and in vivo. Conversely, suppression of miR-146a in aged lin- BMCs increased Plk2 expression and rejuvenated lin- BMCs, resulting in decreased senescence and apoptosis, leading to improved angiogenesis., Conclusions: (1) miR-146a regulates lin- BMC senescence and apoptosis by suppressing Plk2 expression that, in turn, activates p16Ink4a/p19Arf and p53 and (2) modulation of miR-146a or its target Plk2 may represent a potential therapeutic intervention to improve lin- BMC-mediated angiogenesis and vascular repair., (© 2016 American Heart Association, Inc.)

Chronic heart failure (CHF) is the most common cardiac disease among the elderly and a leading cause of mortality in elderly patients. Endothelial dysfunction is held to have a major role in the development and progression of CHF, which results in progressively impaired functional capacity. Endothelial progenitor cells (EPCs) and circulating angiogenic cells (CACs) are the main players involved in the endogenous repair mechanisms that can counteract endothelial dysfunction. A mounting body of data indicates that exercise enhances endothelial renewal through mobilization of bone marrow-derived EPCs and CACs, making it an effective therapeutic tool for CHF. Interestingly, emerging evidence has been showing that exercise training can also promote epigenetic modifications, e.g. DNA methylation, histone modifications, and differential expression of specific non-coding RNAs like microRNA (miRNAs). Since deregulation of the miRNAs involved in endothelial function modulation has widely been documented in circulating cells and plasma of CHF patients, deregulation of epigenetic features could play a key role in disease progression. Here, we review current knowledge of the contribution of EPCs and CACs to endothelial repair mechanisms in CHF patients, focusing on the effects induced by exercise training and hypothesizing that some of these effects can be mediated by epigenetic mechanisms., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Endothelial progenitor cells (EPCs) are mononuclear cells that circulate in the blood and are derived from different tissues, expressing cell surface markers that are similar to mature endothelial cells. The discovery of EPCs has lead to new insights in vascular repair and atherosclerosis and also a new theory for ageing. EPCs from the bone marrow and some other organs aid in vascular repair by migrating to distant vessels where they differentiate into mature endothelial cells and replace old and injured endothelial cells. The ability of EPCs to repair vascular damage depends on their number and functionality. Currently marketed drugs used in a variety of diseases can modulate these characteristics. In this review, the effect of currently available treatment options for cardiovascular and metabolic disorders on EPC biology will be discussed. The various EPC-based therapies that will be discussed include lipid-lowering agents, antihypertensive agents, antidiabetic drugs, phosphodiesteraze inhibitors, hormones, as well as EPC capturing stents., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

To determine whether the presence of ischemic heart disease (IHD) per se, or rather the co-presence of heart failure (HF), is the primum movens for less effective stem cell products in autologous stem cell therapy, we assessed numbers and function of bone marrow (BM)-derived progenitor cells in patients with coronary artery disease (n = 17), HF due to ischemic cardiomyopathy (n = 8), non-ischemic HF (n = 7), and control subjects (n = 11). Myeloid and erythroid differentiation capacity of BM-derived mononuclear cells was impaired in patients with underlying IHD but not with non-ischemic HF. Migration capacity decreased with increasing IHD severity. Hence, IHD, with or without associated cardiomyopathy, is an important determinant of progenitor cell function. No depletion of hematopoietic and endothelial progenitor cells (EPC) within the BM was observed, while circulating EPC numbers were increased in the presence of IHD, suggesting active recruitment. The observed myelosuppression was not driven by inflammation and thus other mechanisms are at play., Competing Interests: Compliance with Ethical Standards The study complied with the Helsinki Declaration and was approved by the local ethics committee. Informed consent was obtained from all subjects. Funding The work was supported by a research grant from the Fund for Scientific Research (FWO-Flanders, G060321N). EN is supported by a research grant from the University of Antwerp. EVC is supported by FWO-Flanders as senior clinical investigator. Competing Interests The authors declare that they have no competing interests.

Air pollution is a major challenge to public health. Ambient fine particulate matter (PM) is the key component for air pollution, and associated with significant mortality. The majority of the mortality following PM exposure is related to cardiovascular diseases. However, the mechanisms for the adverse effects of PM exposure on cardiovascular system remain largely unknown and under active investigation. Endothelial dysfunction or injury is considered one of the major factors that contribute to the development of cardiovascular diseases such as atherosclerosis and coronary heart disease. Endothelial progenitor cells (EPCs) play a critical role in maintaining the structural and functional integrity of vasculature. Particulate matter exposure significantly suppressed the number and function of EPCs in animals and humans. However, the mechanisms for the detrimental effects of PM on EPCs remain to be fully defined. One of the important mechanisms might be related to increased level of reactive oxygen species (ROS) and inflammation. Bone marrow (BM) is a major source of EPCs. Thus, the number and function of EPCs could be intimately associated with the population and functional status of stem cells (SCs) in the BM. Bone marrow stem cells and other SCs have the potential for cardiovascular regeneration and repair. The present review is focused on summarizing the detrimental effects of PM exposure on EPCs and SCs, and potential mechanisms including ROS formation as well as clinical implications., (© 2016 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

Objective: To observe the effect of electroacupuncture (EA) on CD 34+ endothelial progenitor cells (EPCs) in bone marrow and peripheral blood and the expression of p-AKT protein in bone marrow in focal cerebral ischemia/reperfusion (CI/R) rats, so as to investigate its mechanism underlying improvement of cerebral ischemia., Methods: A total of 108 male SD rats were randomly divided into sham operation (sham) group, model (CI/R) group, and EA group which were further divided into 12, 24, 48 h subgroups (n = 12/group, 6 rats for biochemical analysis and the other 6 rats for Western blot analysis). Cl/R model was established by occlusion of the right middle cerebral artery for 2 hours followed by reperfusion. EA (2 Hz/20 Hz) was applied to "Baihui"(GV 20), left "Hegu" (LI 4) and left "Taichong" (LR 3) acupoints for 30 min, once daily. The neurological deficit scores were evaluated using Longa 5-grade standards. Flow cytometer was used to detect the percentages of CD 34+ EPCs in bone marrow and peripheral blood. The expression of p-AKT protein of bone marrow was detected by Western blot., Results: In comparison with the CIl/R model group, the neurological deficit score were gradually and significantly decreased 48 h after CI/R in the EA group (P<0. 05), suggesting an improvement of the neurological function after EA. Compared with the sham group, the percentages of CD 34+ EPCs in bone marrow and peripheral blood and the expression level of bone-marrow p-AKT protein were significantly up-regulated in the model group at the three time-points after CI/R (P<0. 01, P<0. 05). Following EA intervention, the percentages of CD 34+ EPCs at the three time-points in the peripheral blood, and at time-points of 12 h and 24 h in the bone marrow, and the expression levels of p-AKT protein at the three time-points were significantly further up-regulated in the EA group in comparison with the model group (P<0.05, P<0.01)., Conclusion: EA can effectively up-regulate the percentages of CD 34+ EPCs in the bone marrow and peripheral blood, and increase p-AKT protein expression in the bone marrow in CI/R rats, which may contribute to its effect in improving neurological function.

Endothelial progenitor cells (EPCs), a group of bone marrow-derived pro-angiogenic cells, contribute to vascular repair after damage. EPC dysfunction exists in diabetes and results in poor wound healing in diabetic patients with trauma or surgery. The aim of the present study was to determine the effect of quercetin, a natural flavonoid on high glucose‑induced damage in EPCs. Treatment with high glucose (40 mM) decreased cell viability and migration, and increased oxidant stress, as was evidenced by the elevated levels of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase in bone marrow-derived EPCs. Moreover, high glucose reduced the levels of endothelial nitric oxide synthase (eNOS) phosphorylation, nitric oxide (NO) production and intracellular cyclic guanosine monophosphate (cGMP). Quercetin supplement protected against high glucose‑induced impairment in cell viability, migration, oxidant stress, eNOS phosphorylation, NO production and cGMP levels. Quercetin also increased Sirt1 expression in EPCs. Inhibition of Sirt1 by a chemical antagonist sirtinol abolished the protective effect of quercetin on eNOS phosphorylation, NO production and cGMP levels following high glucose stress. To the best of our knowledge, the results provide the first evidence that quercetin protects against high glucose‑induced damage by inducing Sirt1-dependent eNOS upregulation in EPCs, and suggest that quercetin is a promising therapeutic agent for diabetic patients undergoing surgery or other invasive procedures.