Mobilization of endothelial progenitor cells in acute cardiovascular events in the PROCELL study: Time-course after acute myocardial infarction and stroke

Modified Risk Tobacco Products and Cardiovascular Repair: Still Very "Smoky"

Smoking habits represent a cardiovascular risk factor with a tremendous impact on health. Other than damaging differentiated and functional cells of the cardiovascular system, they also negatively affect reparative mechanisms, such as those involved in cardiac fibrosis and in endothelial progenitor cell (EPC) activation. In recent years, alternative smoking devices, dubbed modified tobacco risk products (MRPs), have been introduced, but their precise impact on human health is still under evaluation. Also, they have not been characterized yet about the possible negative effects on cardiovascular reparative and regenerative cells, such as EPCs or pluripotent stem cells. In this perspective, we critically review the still scarce available data on the effects of MRPs on molecular and cellular mechanisms of cardiovascular repair and regeneration.

Hyperlipidemia attenuates the mobilization of endothelial progenitor cells induced by acute myocardial ischemia via VEGF/eNOS/NO/MMP-9 pathway

This study aims to explore the role of hyperlipidemia in the mobilization of bone marrow (BM) endothelial progenitor cells (EPCs) induced by acute myocardial ischemia (AMI). To establish the hyperlipidemia complicated with AMI (HL-AMI) model, SD rats were intragastrically administered the high-fat emulsion for 4 weeks. Then their left anterior descending arteries were ligated. Rats in each group were randomly subdivided into seven subgroups. During 1st ~ 7th day following AMI modeling, rats in 1st ~ 7th subgroups were selected to be phlebotomized from their celiac artery after being anesthetized by pentobarbitone in turn. The quantity of circulating EPCs (CEPCs) was detected by flow cytometry, the expression of VEGF, eNOS, NO, MMP-9 in myocardial tissue was analyzed by western blot, and their plasma level was assayed by ELISA. Dynamic curves were plotted using these data. Within 7 days following AMI, compared with the AMI rats, in the HL-AMI rats, the myocardial infarct size, the plasma activity of CK, CK-MB, and the collagen deposition all remained at the higher levels; meanwhile, these rats showed more significant decreases in the count of CEPCs, the plasma level of VEGF etc., and their expression in myocardial tissue (P < 0.05 or P < 0.01). Our study showed that hyperlipidemia may attenuate the mobilization of BM EPCs induced by AMI via VEGF/eNOS/NO/MMP-9 signal pathway, which might partly account for hyperlipidemia hampering the repairs of AMI-induced cardiac injury.

Protective Effect of CXCR4 Antagonist DBPR807 against Ischemia-Reperfusion Injury in a Rat and Porcine Model of Myocardial Infarction: Potential Adjunctive Therapy for Percutaneous Coronary Intervention

CXCR4 antagonists have been claimed to reduce mortality after myocardial infarction in myocardial infarction (MI) animals, presumably due to suppressing inflammatory responses caused by myocardial ischemia-reperfusion injury, thus, subsequently facilitating tissue repair and cardiac function recovery. This study aims to determine whether a newly designed CXCR4 antagonist DBPR807 could exert better vascular-protective effects than other clinical counterparts (e.g., AMD3100) to alleviate cardiac damage further exacerbated by reperfusion. Consequently, we find that instead of traditional continuous treatment or multiple-dose treatment at different intervals of time, a single-dose treatment of DBPR807 before reperfusion in MI animals could attenuate inflammation via protecting oxidative stress damage and preserve vascular/capillary density and integrity via mobilizing endothelial progenitor cells, leading to a desirable fibrosis reduction and recovery of cardiac function, as evaluated with the LVEF (left ventricular ejection fraction) in infarcted hearts in rats and mini-pigs, respectively. Thus, it is highly suggested that CXCR4 antagonists should be given at a single high dose prior to reperfusion to provide the maximal cardiac functional improvement. Based on its favorable efficacy and safety profiles indicated in tested animals, DBPR807 has a great potential to serve as an adjunctive medicine for percutaneous coronary intervention (PCI) therapies in acute MI patients.

Soluble Flt-1 in AMI Patients Serum Inhibits Angiogenesis of Endothelial Progenitor Cells by Suppressing Akt and Erk’s Activity

Simple Summary

Acute myocardial infarction (AMI) is the leading cause of mortality in the world. Endothelial progenitor cells (EPCs) exert important roles in the recovery of collateral circulation via angiogenesis. In this study, we studied the characteristics of EPCs isolated from the peripheral blood of AMI patients and healthy subjects. We found that the number of EPCs increased in AMI patients and exhibited faster migration compared to healthy subjects. However, no difference in angiogenic activity was observed in EPCs between AMI patients and healthy subjects. Interestingly, the serum level of sFlt-1 was elevated in AMI patients. Further analysis demonstrated that sFlt-1 inhibited EPCs angiogenesis in vitro by inhibiting the Akt and Erk signaling pathways. In conclusion, our study uncovered that EPCs increased in quantity, but their angiogenesis activity was inhibited by serum sFlt-1 in AMI patients.

Abstract

In acute myocardial infarction (AMI), endothelial progenitor cells (EPCs) are essential for the recovery of collateral circulation via angiogenesis. Clinical research has shown that the poor prognosis of the patients with AMI is closely associated with the cell quantity and function of EPCs. Whether there are differences in the biological features of EPCs from AMI patients and healthy subjects is worth exploring. In this study, EPCs were isolated from human peripheral blood and identified as late-stage EPCs by flow cytometry, immunofluorescence, and blood vessel formation assay. Compared to healthy subjects, AMI patients had more EPCs in the peripheral blood compared to healthy subjects. In addition, EPCs from AMI patients exhibited higher migration ability in the transwell assay compared to EPCs from healthy subjects. However, no difference in the angiogenesis of EPCs was observed between AMI patients and healthy subjects. Further studies revealed that soluble vascular endothelial growth factor receptor 1 (sFlt-1) in the serum of AMI patients was involved in the inhibition of EPCs angiogenesis by suppressing the Akt and Erk pathways. In conclusion, this study demonstrated that elevated serum sFlt-1 inhibits angiogenesis of EPC in AMI patients. Our findings uncover a pathogenic role of sFlt-1 in AMI.

Endothelial Progenitor Cell Levels and Extent of Post-prandial Lipemic Response

Background and Objective

Due to the frequency of meal ingestion, individuals spend the majority of the day, ~18 h, in a status of post-prandial (PP) stress. Remnant-like lipoprotein particles (RLPs) are predominant in PP phase playing an important role in the development of atherosclerosis. Endothelial progenitor cells (EPCs) have been suggested to play a role in vessel wall homeostasis and in reducing atherosclerosis. However, there is no information about peripheral blood EPCs number following PP stress. We investigated the association between circulating EPCs levels and extent of PP lipemia in healthy subjects following a high-fat meal.

Materials and Methods

A total of 84 healthy subjects (42 men, 42 women) aged 17–55 years were included in the study. PP lipemic response of subjects was determined by Oral Fat-Loading Test (OFLT). All the subjects were classified on the basis of their plasma TG levels after PP lipemic stressors in categories 1 (low), 2 (moderate), and 3 (high). Circulating EPCs numbers were measured by the flow cytometry method.

Results

There was a significant difference in terms of lipid parameters between men and women: high-density lipoprotein cholesterol (HDL-C) was significantly lower in men than in women (p &lt; 0.001). Total cholesterol (TC) (p = 0.004), low-density lipoprotein cholesterol (LDL-C) (p &lt; 0.001), triglyceride (TG) (p &lt; 0.001), and TG-AUC (p &lt; 0.001) were significantly higher in men than in women. There was no significant difference between the genders in terms of CD34+KDR+ and CD34+KDR+CD133+cell number and MMP-9 levels. Vascular endothelial growth factor (VEGF) levels were significantly higher in men than women (p = 0.004). TC, LDL-C, and TG were significantly higher in the 3rd category than 1st and 2nd categories (p &lt; 0.001) in women. Age, body mass index (BMI), fat rate, TG, TC, and LDL-C were significantly higher in the 3rd category than 1st category (p &lt; 0.001, p = 0.002, p = 0.002, p = 0.01, p = 0.007, p = 0.004; respectively), in men. Circulating numbers of EPCs in men were significantly higher in the PP hyperlipidemia group than in the low TG levels category, independently from age (p &lt; 0.05). Circulating EPC levels showed a positive correlation with OFLT response in men (r = 0.414, p &lt; 0.05). Also, OFLT response showed a strong positive correlation with fasting TG levels (r = 0.930, p &lt; 0.001). EPC levels in categories of women were not different.

Conclusion

Increased EPCs levels in subjects with different PP hyperlipidemia may be associated with a response to endothelial injury, related to increased atherogenic remnant particles at the PP phase.

Secretome of endothelial progenitor cells from stroke patients promotes endothelial barrier tightness and protects against hypoxia-induced vascular leakage

BACKGROUND

Cell-based therapeutic strategies have been proposed as an alternative for brain repair after stroke, but their clinical application has been hampered by potential adverse effects in the long term. The present study was designed to test the effect of the secretome of endothelial progenitor cells (EPCs) from stroke patients (scCM) on in vitro human models of angiogenesis and vascular barrier.

METHODS

Two different scCM batches were analysed by mass spectrometry and a proteome profiler. Human primary CD34+-derived endothelial cells (CD34+-ECs) were used for designing angiogenesis studies (proliferation, migration, and tubulogenesis) or in vitro models of EC monolayer (confluent monolayer ECs-CMECs) and blood-brain barrier (BBB; brain-like ECs-BLECs). Cells were treated with scCM (5 μg/mL) or protein-free endothelial basal medium (scEBM-control). CMECs or BLECs were exposed (6 h) to oxygen-glucose deprivation (OGD) conditions (1% oxygen and glucose-free medium) or normoxia (control-5% oxygen, 1 g/L of glucose) and treated with scCM or scEBM during reoxygenation (24 h).

RESULTS

The analysis of different scCM batches showed a good reproducibility in terms of protein yield and composition. scCM increased CD34+-EC proliferation, tubulogenesis, and migration compared to the control (scEBM). The proteomic analysis of scCM revealed the presence of growth factors and molecules modulating cell metabolism and inflammatory pathways. Further, scCM decreased the permeability of CMECs and upregulated the expression of the junctional proteins such as occludin, VE-cadherin, and ZO-1. Such effects were possibly mediated through the activation of the interferon pathway and a moderate downregulation of Wnt signalling. Furthermore, OGD increased the permeability of both CMECs and BLECs, while scCM prevented the OGD-induced vascular leakage in both models. These effects were possibly mediated through the upregulation of junctional proteins and the regulation of MAPK/VEGFR2 activity.

CONCLUSION

Our results suggest that scCM promotes angiogenesis and the maturation of newly formed vessels while restoring the BBB function in ischemic conditions. In conclusion, our results highlight the possibility of using EPC-secretome as a therapeutic alternative to promote brain angiogenesis and protect from ischemia-induced vascular leakage.

Circulating exosomal miR-144-3p inhibits the mobilization of endothelial progenitor cells post myocardial infarction via regulating the MMP9 pathway

Background: The angiogenesis post myocardial infarction (MI) is compromised in diabetes. MiR-144-3p is reported to be highly expressed in circulating exosomes of diabetic patients, implying its role in diabetic complications. However, whether circulating exosomes and enriched miR-144-3p are involved in the impaired neovascularization in diabetes and the underlying mechanism is unclear.

Results: DMexo and miR-144-3p mimic-treated MSCs had elevated miR-144-3p levels and decreased MMP9, Ets1 and PLG expression. The percentage of EPCs were relatively lower in DMexo-treated or agomir-treated MI mice compared with MI mice. Finally, the luciferase assay confirmed the direct binding between miR-144-3p and Ets1.

Conclusion: Exosomal miR-144-3p could impair the mobilization ability of EPCs, which was associated with impaired ischemia-induced neovascularization.

Methods: Circulating exosomes were isolated from Streptozotocin (STZ)-induced mice. In vitro, mesenchymal stem cells (MSCs) were incubated with exosomes from diabetic mice (DMexo), and miR-144-3p mimic or inhibitor. miR-144-3p, and MMP9 pathway were measured using qPCR and immunoblotting. In vivo, MI mice induced by left anterior descending ligation were treated with DMexo, as well as miR-144-3p agomir. Flow cytometry was used to profile endothelial progenitor cells (EPCs) in peripheral blood and bone marrow post 24 hours respectively.

Autologous Bone Marrow Mononuclear Cell Transplantation Therapy Improved Symptoms in Patients with Refractory Diabetic Sensorimotor Polyneuropathy via the Mechanisms of Paracrine and Immunomodulation: A Controlled Study

We recently reported that transplantation of autologous bone marrow mononuclear cells (BM-MNCs) may be an effective and promising therapy to treat refractory diabetic sensorimotor polyneuropathy (DSPN) in patients with type 2 diabetes mellitus (T2DM). This study was designed to investigate the potential mechanisms of BM-MNCs therapy, which recruited 60 patients with DSPN, 30 T2DM patients without complications, and 30 healthy control participants. All clinical parameters, the levels of inflammatory markers, and growth factors in the three groups were compared. Patients in DSPN group had higher level of tumor necrosis factor-α (TNF-α) (DSPN vs control, 412.90 ± 64.58 vs 374.81 ± 63.18 pg/mL, P < 0.01) and lower level of vascular endothelial growth factor (VEGF) (DSPN vs control, 140.93 ± 24.78 vs 157.39 ± 25.11 pg/mL, P < 0.01) than those in control group. DSPN group had the highest level of soluble intercellular adhesion molecule-1 (sICAM-1) among three groups (DSPN and DM vs control, 1477.56 ± 228.00 and 1342.17 ± 237.54 vs 1308.00 ± 200.94 ng/mL, P < 0.05). The level of nerve growth factor in the DSPN group was slightly lower than that in the DM group (DSPN vs DM, 3509.11 ± 438.39 vs 3734.87 ± 647.50 pg/mL, P < 0.05). All patients with DSPN received one intramuscular injection of BM-MNCs and clinical follow-ups after the therapy for 2 days, 1, 4, 12, 24, and 48 weeks. Neuropathic symptoms of foot pain, numbness, and weakness were significantly improved within 4 weeks after BM-MNCs injection. Patients with DSPN were divided into the responder (n = 35) and nonresponder groups (n = 19) based on the improvement of nerve conduction velocity at 12 weeks post-transplantation. Compared with nonresponders, responders were younger (57.3 ± 5.2 vs 62.0 ± 4.8, P < 0.01), had a shorter history of diabetes (7.1 ± 2.7 vs 11.2 ± 5.4 years, P < 0.01), and had higher numbers of mobilized CD34⁺ cells (17.61 ± 2.64 vs 14.79 ± 1.62 ×10⁵/L, P < 0.01) and BM-MNCs (12.05 ± 2.16 vs 9.84 ± 1.53 ×10⁸/L, P < 0.01). The levels of TNF-α and sICAM-1 decreased just after BM-MNCs injection in both groups and slowly reverted to baseline levels. The duration of the downtrend of TNF-α and sICAM-1 in the responder group lasted longer than that in the nonresponder group. Serum level of VEGF in the responder group increased immediately after BM-MNC therapy and reached the highest point after the injection for 12 weeks. On the other hand, VEGF levels in the nonresponder group only increased slightly. Binary logistic regression was performed to evaluate the corresponding prognostic factors for BM-MNCs treatment. The number of applied CD34⁺ cells and the duration of diabetes were the independent predictors of responding to BM-MNCs therapy. No adverse event associated with the treatment was observed during follow-up observations. These results indicated that BM-MNCs transplantation is an effective and promising therapeutic strategy to treat refractory DSPN. The immune regulation and paracrine function of BM-MNCs may contribute to the improvement of DSPN.

Intrinsic Vascular Repair by Endothelial Progenitor Cells in Acute Coronary Syndromes: an Update Overview

Bone marrow-derived endothelial progenitor cells (EPCs) play a key role in the maintenance of endothelial homeostasis and endothelial repair at areas of vascular damage. The quantification of EPCs in peripheral blood by flow cytometry is a strategy to assess this reparative capacity. The number of circulating EPCs is inversely correlated with the number of cardiovascular risk factors and to the occurrence of cardiovascular events. Therefore, monitoring EPCs levels may provide an accurate assessment of susceptibility to cardiovascular injury, greatly improving risk stratification of patients with high cardiovascular risk, such as those with an acute myocardial infarction. However, there are many issues in the field of EPC identification and quantification that remain unsolved. In fact, there have been conflicting protocols used to the phenotypic identification of EPCs and there is still no consensual immunophenotypical profile that corresponds exactly to EPCs. In this paper we aim to give an overview on EPCs-mediated vascular repair with special focus on acute coronary syndromes and to discuss the different phenotypic profiles that have been used to identify and quantify circulating EPCs in several clinical studies. Finally, we will synthesize evidence on the prognostic role of EPCs in patients with high cardiovascular risk.

Endothelial Progenitor Cells as a Marker of Vascular Damage But not a Predictor in Acute Microangiopathy-Associated Stroke

Background: The aim of the study was to assess the number of endothelial progenitor cells (EPCs) in patients with acute stroke due to cerebral microangiopathy and evaluate whether there is a relationship between their number and clinical status, radiological findings, risk factors, selected biochemical parameters, and prognosis, both in ischemic and hemorrhagic stroke. Methods: In total, 66 patients with lacunar ischemic stroke, 38 patients with typical location hemorrhagic stroke, and 22 subjects from the control group without acute cerebrovascular incidents were included in the prospective observational study. The number of EPCs was determined in serum on the first and eighth day after stroke onset using flow cytometry and identified with the immune-phenotype classification determinant (CD)45−, CD34+, CD133+. Results: We demonstrated a significantly higher number of EPCs on the first day of stroke compared to the control group (med. 17.75 cells/µL (0–488 cells/µL) vs. 5.24 cells/µL (0–95 cells/µL); p = 0.0006). We did not find a relationship between the number of EPCs in the acute phase of stroke and the biochemical parameters, vascular risk factors, or clinical condition. In females, the higher number of EPCs on the first day of stroke is related to a favorable functional outcome on the eighth day after the stroke onset compared to males (p = 0.0355). We found that a higher volume of the hemorrhagic focus on the first day was correlated with a lower number of EPCs on the first day (correlation coefficient (R) = −0.3378, p = 0.0471), and a higher number of EPCs on the first day of the hemorrhagic stroke was correlated with a lower degree of regression of the hemorrhagic focus (R = −0.3896, p = 0.0367). Conclusion: The study showed that endothelial progenitor cells are an early marker in acute microangiopathy-associated stroke regardless of etiology and may affect the radiological findings in hemorrhagic stroke. Nevertheless, their prognostic value remains doubtful in stroke patients.

Exosomes from SIRT1-Overexpressing ADSCs Restore Cardiac Function by Improving Angiogenic Function of EPCs

Acute myocardial infarction (AMI) is one of the leading causes of mortality in cardiovascular diseases. The aim of this study was to investigate whether exosomes from Sirtuin 1 (SIRT1)-overexpressing adipose-derived stem cells (ADSCs) had a protective effect on AMI. The expression of C-X-C chemokine receptor type 7 (CXCR7) was significantly downregulated in peripheral blood endothelial progenitor cells (EPCs) from AMI patients (AMI-EPCs) compared with that in healthy donors, which coincided with impaired tube formation. The exosomes from SIRT1 overexpression in ADSCs (ADSCs-SIRT1-Exos) increased the expression of C-X-C motif chemokine 12 (CXCL12) and nuclear factor E2 related factor 2 (Nrf2) in AMI-EPCs, which promoted migration and tube formation of AMI-EPCs, and overexpression of CXCR7 helped AMI-EPCs to restore the function of cell migration and tube formation. Moreover, CXCR7 was downregulated in the myocardium of AMI mice, and knockout of CXCR7 exacerbated AMI-induced impairment of cardiovascular function. Injection of ADSCs-SIRT1-Exos increased the survival and promoted the recovery of myocardial function with reduced infarct size and post-AMI left ventricular remodeling, induced vasculogenesis, and decreased AMI-induced myocardial inflammation. These findings showed that ADSCs-SIRT1-Exos may recruit EPCs to the repair area and that this recruitment may be mediated by Nrf2/CXCL12/CXCR7 signaling.

Circulating angiogenic cells in glioblastoma: toward defining crucial functional differences in CAC-induced neoplastic versus reactive neovascularization

Background

In order to identify suitable therapeutic targets for glioma anti-angiogenic therapy, the process of neovascularization mediated by circulating angiogenic cells (CACs) needs to be scrutinized.

Methods

In the present study, we compared the expression of neovascularization-related genes by 3 circulating CAC subsets (hematopoietic progenitor cells [HPCs], CD34⁺, and KDR⁺ cells; internal controls: peripheral blood mononuclear cells and circulating endothelial cells) of treatment-naïve patients with glioblastoma (GBM) to those of patients undergoing reactive neovascularization (myocardial infarction (MI). CACs from umbilical cord (representing developmental neovascularization) and healthy subjects served as controls. Fluorescent-activated cell sorting was used to isolate CACs, RT-PCR to determine the expression levels of a panel of 48 neovascularization-related genes, and Luminex assays to measure plasma levels of 21 CAC-related circulating molecules.

Results

We found essential differences in gene expression between GBM and MI CACs. GBM CACs had a higher expression of proangiogenic factors (especially, KITL, CXCL12, and JAG1), growth factor and chemotactic receptors (IGF1R, TGFBR2, CXCR4, and CCR2), adhesion receptor monomers (ITGA5 and ITGA6), and matricellular factor POSTN. In addition, we found major differences in the levels of neovascularization-related plasma factors. A strong positive correlation between plasma MMP9 levels and expression of CXCR4 in the CAC subset of HPCs was found in GBM patients.

Conclusions

Our findings indicate that CAC-mediated neovascularization in GBM is characterized by more efficient CAC homing to target tissue and a more potent proangiogenic response than in physiologic tissue repair in MI. Our findings can aid in selecting targets for therapeutic strategies acting against GBM-specific CACs.

Novel Insight into Neuroimmune Regulatory Mechanisms and Biomarkers Linking Major Depression and Vascular Diseases: The Dilemma Continues

Major depressive disorder (MDD) represents a serious health problem estimated to affect 350 million people globally. Importantly, MDD has repeatedly emerged as an etiological or prognostic factor in cardiovascular disease (CVD) development, including vascular pathology. Several linking pathomechanisms between MDD and CVD involve abnormal autonomic regulation, inflammation, and endothelial dysfunction as an early preclinical stage of atherosclerosis. However, the cause of accelerated atherosclerosis in MDD patients remains unclear. Recently, the causal relationships between MDD and mediator (e.g., inflammation and/or endothelial dysfunction), as well as the causal pathways from the mediator to atherosclerosis, were discussed. Specifically, MDD is accompanied by immune dysregulation, resulting in increased production of proinflammatory cytokines (e.g., interleukin (IL)-6 and tumor necrosis factor (TNF)-α), which could lead to depression-linked abnormalities in brain function. Further, MDD has an adverse effect on endothelial function; for example, circulating markers of endothelial dysfunction (e.g., soluble adhesion molecules, von Willebrand factor) have been linked with depression. Additionally, MDD-linked autonomic dysregulation, which is characterized by disrupted sympathovagal balance associated with excessive circulating catecholamines, can contribute to CVD. Taken together, activated inflammatory response, endothelial dysfunction, and autonomic dysregulation could affect gradual atherosclerosis progression, resulting in a higher risk of developing CVD in MDD. This review focused on the pathomechanisms linking MDD and CVD with respect to neuroimmune regulation, and the description of promising biomarkers, which is important for the early diagnosis and personalized prevention of CVD in major depression.

MicroRNA-326-5p enhances therapeutic potential of endothelial progenitor cells for myocardial infarction

Background

Our study sought to investigate the therapeutic effects and mechanisms of miR-326-5p-overexpressing endothelial progenitor cells (EPCs) on acute myocardial infarction (AMI).

Methods

Mouse EPCs were isolated, purified, and identified by flow cytometry and uptake of DiI-ac-LDL. The target gene of miR-326-5p was predicted using target prediction algorithms and verified by dual-luciferase reporter assay, RT-qPCR, and Western blot. After EPCs were transfected with the agomir or antagomir of miR-326-5p, tube formation assay and Matrigel plug angiogenesis assay were conducted in four groups (NC, miR-326-5p agomir, miR-326-5p antagomir, and miR-326-5p agomir+Wnt1 agonist). In addition, a mouse model of MI was established and treated with the injection of miR-326-5p-EPCs, miR-326-5p-EPCs+ Wnt1 agonist, EPCs-NC, or PBS/control into the peri-infarcted myocardium. Subsequently, cardiac function was monitored by echocardiography at 7 and 28 days postoperatively. Finally, the infarcted hearts were collected at 28 days, and the size of myocardial infarction was measured by Masson’s trichrome staining and the neovascularization in the peri-infarcted area was examined through immunofluorescence staining.

Results

Luciferase reporter assay indicated that Wnt1 was a direct target of miR-326-5p. Using RT-qPCR and Western blot analysis, we further demonstrated that the expression level of Wnt1 was negatively correlated with miR-326-5p expression in EPCs. Both in vitro study of tube formation assay and in vivo investigation of subcutaneous Matrigel plug assay revealed that the miR-326-5p agomir could significantly enhance the angiogenic capacity of EPCs, and this effect was partially inhibited by Wnt1 agonist. Meanwhile, miR-326-5p antagomir could obviously reduce the the angiogenic capacity of EPCs in vivo compared with that in the NC group. Moreover, the transplantation of miR-326-5p-overexpressing EPCs in the ischemic hearts of mice significantly enhanced the angiogenesis in the peri-infarcted zone and improved the cardiac function. However, the enhanced capacity of angiogenesis of miR-326-5p-overexpressing EPCs was remarkably neutralized by Wnt1 agonist, accompanied by the decreased improvement in cardiac function.

Conclusion

miR-326-5p significantly enhanced the angiogenic capacity of EPCs. Transplantation of miR-326-5p-overexpressing EPCs improved cardiac function for AMI therapy, which can be a novel strategy for enhancing therapeutic angiogenesis in ischemic heart diseases.

Endothelial Ca2+ Signaling, Angiogenesis and Vasculogenesis: just What It Takes to Make a Blood Vessel

It has long been known that endothelial Ca²⁺ signals drive angiogenesis by recruiting multiple Ca²⁺-sensitive decoders in response to pro-angiogenic cues, such as vascular endothelial growth factor, basic fibroblast growth factor, stromal derived factor-1α and angiopoietins. Recently, it was shown that intracellular Ca²⁺ signaling also drives vasculogenesis by stimulation proliferation, tube formation and neovessel formation in endothelial progenitor cells. Herein, we survey how growth factors, chemokines and angiogenic modulators use endothelial Ca²⁺ signaling to regulate angiogenesis and vasculogenesis. The endothelial Ca²⁺ response to pro-angiogenic cues may adopt different waveforms, ranging from Ca²⁺ transients or biphasic Ca²⁺ signals to repetitive Ca²⁺ oscillations, and is mainly driven by endogenous Ca²⁺ release through inositol-1,4,5-trisphosphate receptors and by store-operated Ca²⁺ entry through Orai1 channels. Lysosomal Ca²⁺ release through nicotinic acid adenine dinucleotide phosphate-gated two-pore channels is, however, emerging as a crucial pro-angiogenic pathway, which sustains intracellular Ca²⁺ mobilization. Understanding how endothelial Ca²⁺ signaling regulates angiogenesis and vasculogenesis could shed light on alternative strategies to induce therapeutic angiogenesis or interfere with the aberrant vascularization featuring cancer and intraocular disorders.

Circulating Proangiogenic Cells and Proteins in Patients with Glioma and Acute Myocardial Infarction: Differences in Neovascularization between Neoplasia and Tissue Regeneration

Although extensive angiogenesis takes place in glial tumors, antiangiogenic therapies have remained without the expected success. In the peripheral circulation of glioma patients, increased numbers of endothelial precursor cells (EPCs) are present, potentially offering targets for antiangiogenic therapy. However, for an antiangiogenic therapy to be successful, the therapy should specifically target glioma-related EPC subsets and secreted factors only. Here, we compared the EPC subsets and plasma factors in the peripheral circulation of patients with gliomas to acute myocardial infarctions. We investigated the five most important EPC subsets and 21 angiogenesis-related plasma factors in peripheral blood samples of 29 patients with glioma, 14 patients with myocardial infarction, and 20 healthy people as controls, by FACS and Luminex assay. In GBM patients, all EPC subsets were elevated as compared to healthy subjects. In addition, HPC and KDR⁺ cell fractions were higher than in MI, while CD133⁺ and KDR⁺CD133⁺ cell fractions were lower. There were differences in relative EPC fractions between the groups: KDR⁺ cells were the largest fraction in GBM, while CD133⁺ cells were the largest fraction in MI. An increase in glioma malignancy grade coincided with an increase in the KDR⁺ fraction, while the CD133⁺ cell fraction decreased relatively. Most plasma angiogenic factors were higher in GBM than in MI patients. In both MI and GBM, the ratio of CD133⁺ HPCs correlated significantly with elevated levels of MMP9. In the GBM patients, MMP9 correlated strongly with levels of all HPCs. In conclusion, the data demonstrate that EPC traffic in patients with glioma, representing neoplasia, is different from that in myocardial infarction, representing tissue regeneration. Glioma patients may benefit from therapies aimed at lowering KDR⁺ cells and HPCs.

Coronary circulating mononuclear progenitor cells and soluble biomarkers in the cardiovascular prognosis after coronary angioplasty

Currently, there are no confident prognostic markers in patients with coronary artery disease (CAD) undergoing angioplasty. The present study aimed to explore whether basal coronary circulating Mononuclear Progenitor Cells (MPCs) and vascular injury biomarkers were related to development of major adverse cardiovascular events (MACEs) and may impact clinical prognosis.

Methods

The number of MPCs and soluble mediators such as IL‐1β, sICAM‐1, MMP‐9, malondialdehyde, superoxide dismutase and nitric oxide were determined in coronary and peripheral circulation. Prognostic ability for MACEs occurring at 6 months follow up was assessed by time‐to‐event and event free survival estimations.

Results

Lower coronary circulating MPCs subpopulations CD45⁺CD34⁺, CD45⁺CD34⁺CD133⁺CD184⁺, lower MMP‐9 and higher sICAM‐1 significantly associated with MACEs presentation and showed prognostic ability; while peripheral blood increase in malondialdehyde and decreased superoxide dismutase were observed in patients with MACEs.

Conclusion

Coronary concentration of biomarkers related with vascular repair, such as MPCs subpopulations and adhesion molecules, may predict MACEs and impact prognosis in patients with CAD undergoing angioplasty; whereas peripheral pro‐oxidative condition may be also associated.

Rapid and selective mobilization of specific stem cell types after consumption of a polyphenol-rich extract from sea buckthorn berries (Hippophae) in healthy human subjects

Purpose

The aim of this study was to evaluate the effects of a proanthocyanidin-rich extract of sea buckthorn berry (SBB-PE) on the numbers of various types of adult stem cells in the blood circulation of healthy human subjects.

Study design and methods

A randomized, double-blind, placebo-controlled, cross-over trial was conducted in 12 healthy subjects. Blood samples were taken immediately before and at 1 and 2 hours after consuming either placebo or 500 mg SBB-PE. Whole blood was used for immunophenotyping and flow cytometry to quantify the numbers of CD45dim CD34+ CD309+ and CD45dim CD34+ CD309− stem cells, CD45− CD31+ CD309+ endothelial stem cells, and CD45− CD90+ mesenchymal stem cells.

Results

Consumption of SBB-PE was associated with a rapid and highly selective mobilization of CD45dim CD34+ CD309− progenitor stem cells, CD45− CD31+ CD309+ endothelial stem cells, and CD45− CD90+ lymphocytoid mesenchymal stem cells. In contrast, only minor effects were seen for CD45dim CD34+ CD309+ pluripotential stem cells.

Conclusion

Consumption of SBB-PE resulted in selective mobilization of stem cell types involved in regenerative and reparative functions. These data may contribute to the understanding of the traditional uses of SBB for preventive health, regenerative health, and postponing the aging process.

The role of endothelial colony forming cells in kidney cancer's pathogenesis, and in resistance to anti-VEGFR agents and mTOR inhibitors: A speculative review

Renal cell carcinoma (RCC) is highly dependent on angiogenesis, due to the overactivation of the VHL/HIF/VEGF/VEGFRs axis; this justifies the marked sensitivity of this neoplasm to antiangiogenic agents which, however, ultimately fail to control tumor growth. RCC also frequently shows alterations in the mTOR signaling pathway, and mTOR inhibitors have shown a similar pattern of initial activity/late failure as pure antiangiogenic agents. Understanding mechanisms of resistance to these agents would be key to improve the outcome of our patients. Circulating endothelial cells are a family of mainly bone marrow-derived progenitors, which have been postulated to be responsible of the reactivation of angiogenesis in different tumors. In this review, we shall discuss the complex nature and function of these cells, the evidence pro and contra their contribution to tumor vascularization, especially as far as RCC is concerned, and their possible role in determining resistance to presently available treatments.

Revascularization and endothelial progenitor cells in stroke

Stroke is one of the leading causes of death and disability worldwide. Tremendous improvements have been achieved in the acute care of stroke patients with the implementation of stroke units, thrombolytic drugs, and endovascular trombectomies. However, stroke survivors with neurological deficits require long periods of neurorehabilitation, which is the only approved therapy for poststroke recovery. With this scenario, more treatments are urgently needed, and only the understanding of the mechanisms of brain recovery might contribute to identify new therapeutic agents. Fortunately, brain injury after stroke is counteracted by the birth and migration of several populations of progenitor cells towards the injured areas, where angiogenesis and vascular remodeling play a key role providing trophic support and guidance during neurorepair. Endothelial progenitor cells (EPCs) constitute a pool of circulating bone-marrow derived cells that mobilize after an ischemic injury with the potential to incorporate into the damaged endothelium, to form new vessels, or to secrete trophic factors stimulating vessel remodeling. The circulating levels of EPCs are altered after stroke, and several subpopulations have proved to boost brain neurorepair in preclinical models of cerebral ischemia. The goal of this review is to discuss the current state of the neuroreparative actions of EPCs, focusing on their paracrine signaling mechanisms thorough their secretome and released extracellular vesicles.

Trichosanthes pericarpium Aqueous Extract Enhances the Mobilization of Endothelial Progenitor Cells and Up-regulates the Expression of VEGF, eNOS, NO, and MMP-9 in Acute Myocardial Ischemic Rats

Trichosanthes pericarpium (TP) had been widely used to cure patients of cardiovascular disease for 2,000 years in China. This study aims to extend our previous work to explore the mechanism underlying the protective effect of TP on acute myocardial ischemia (AMI). We hypothesized that TP may display its protective effect on AMI by promoting the mobilization of endothelial progenitor cells (EPC) via up-regulating the expression level of vascular endothelial growth factor (VEGF), endothelial nitric oxide syntheses (eNOS), nitric oxide (NO), and matrix metalloproteinase 9 (MMP-9) in AMI rats. To confirm this hypothesis, we treated AMI model rats with intragastrical administration of TP aqueous extract (TPAE), and examined both changes in the number of CEPC, and the expression levels of VEGF, eNOS, NO, and MMP-9 in myocardial tissue and their plasma content in these rats. Rats in each group were randomly divided into seven subgroups. From day 1 to 7 following AMI modeling, rats in these subgroups was sequentially phlebotomized from their celiac artery after being anesthetized by chloral hydrate. We found that, compared with the AMI model rats, in rats treated by TPAE, the CEPC counts, the expression of VEGF, eNOS, NO, and MMP-9 in myocardial tissue and their plasma content all increased more rapidly 7 days after AMI and remained at higher level (P < 0.05 or P < 0.01). Our results showed that, in AMI rats, the TPAE could significantly promote the mobilization of EPC and up-regulate the expression level of VEGF, eNOS, NO, and MMP-9 in myocardium and their plasma content. Therefore, our results suggest that TAPE may regulate EPC mobilization through up-regulating the expression level of VEGF, eNOS, NO and MMP-9 in the myocardium of AMI rats.

The role of polysaccharide peptide of Ganoderma lucidum as a potent antioxidant against atherosclerosis in high risk and stable angina patients

Objectives

Antioxidants can reduce oxidative radicals that affect the early phase of atherogenesis, that is endothelial dysfunction. Polysaccharide Peptide (PsP) derived from Ganoderma lucidum has an active substance in the form of β-glucan. Previous studies have proven the PsP of Ganoderma lucidum as an effective antioxidant in atherosclerotic rats and shows no toxicity in animal model. This study aims to prove the effect of PsP as potent antioxidant in high risk and stable angina patients.

Method

This is a clinical trial conducted to 37 high risk and 34 stable angina patients, which were determined based on ESC Stable CAD Guidelines and Framingham risk score, with pre and post test design without control group. The parameters are superoxide dimustase (SOD) and malondialdehyde (MDA) concentration, circulating endothelial cell (CEC) and endothelial progenitor cell (EPC) counts. The patients were given PsP 750 mg/day in 3 divided dose for 90 days. Paired t-test was performed for normally distributed data, and Wilcoxon test for not normally distributed data, and significant level of p ≤ 0,05.

Results

SOD level in high risk patients slightly increased but not statistically significant with p = 0,22. Level of SOD in stable angina group significantly increased with p = 0,001. MDA concentration significantly reduced in high risk and stable angina patients with p = 0.000. CEC significantly reduced both in high risk and stable angina patients, with p = 0.000 in both groups. EPC count significantly reduced in high risk and stable angina with p = 0.000.

Conclusion

PsP of Ganoderma lucidum is a potent antioxidant against pathogenesis of atherosclerosis in stable angina and high risk patients

Myocardial infarction does not affect circulating haematopoietic stem and progenitor cell self-renewal ability in a rat model

NEW FINDINGS

What is the central question of this study? Although peripheral blood haematopoietic stem and progenitor cells are potentially important in regeneration after acute myocardial infarction, their self-renewal ability in the post-acute phase has not yet been addressed. What is the main finding and its importance? In rat peripheral blood, we show that myocardial infarction does not negatively affect circulating haematopoietic stem and progenitor cell self-renewal ability 2 weeks after acute infarction, which suggests a constant regenerative potential in the myocardial infarction post-acute phase. Given the importance of peripheral blood haematopoietic stem and progenitor cells (HPCs) in post-acute regeneration after acute myocardial infarction (MI), the aim of the present study was to investigate the number and secondary replating capacity/self-renewal ability of HPCs in peripheral blood before and 2 weeks after MI. In female Lewis inbred rats (n = 9), MI was induced by ligation of the left coronary artery, and another nine underwent sham surgery, without ligation, for control purposes. Myocardial infarction was confirmed by troponin I concentrations 24 h after surgery. Peripheral blood was withdrawn and fractional shortening and ejection fraction of the left ventricle were assessed before (day 0) and 14 days after MI or sham surgery (day 14). After mononuclear cell isolation, primary and secondary functional colony-forming unit granulocyte-macrophage (CFU-GM) assays were performed in order to detect the kinetics of functional HPC colony counts and cell self-renewal ability in vitro. The CFU-GM counts and cell self-renewal ability remained unchanged (P > 0.05) in both groups at day 14, without interaction between groups. In the intervention group, higher day 0 CFU-GM counts showed a relationship to lower fractional shortening on day 14 (ρ = -0.82; P < 0.01). Myocardial infarction did not negatively affect circulating HPC self-renewal ability, which suggests a constant regenerative potential in the post-acute phase. A relationship of cardiac contractile function 14 days after MI with circulating CFU-GM counts on day 0 might imply functional colony count as a predictive factor for outcome after infarction.

TRPC3-mediated Ca2+ signals as a promising strategy to boost therapeutic angiogenesis in failing hearts: The role of autologous endothelial colony forming cells

Endothelial progenitor cells (EPCs) are a sub-population of bone marrow-derived mononuclear cells that are released in circulation to restore damaged endothelium during its physiological turnover or rescue blood perfusion after an ischemic insult. Additionally, they may be mobilized from perivascular niches located within larger arteries' wall in response to hypoxic conditions. For this reason, EPCs have been regarded as an effective tool to promote revascularization and functional recovery of ischemic hearts, but clinical application failed to exploit the full potential of patients-derived cells. Indeed, the frequency and biological activity of EPCs are compromised in aging individuals or in subjects suffering from severe cardiovascular risk factors. Rejuvenating the reparative phenotype of autologous EPCs through a gene transfer approach has, therefore, been put forward as an alternative approach to enhance their therapeutic potential in cardiovascular patients. An increase in intracellular Ca²⁺ concentration constitutes a pivotal signal for the activation of the so-called endothelial colony forming cells (ECFCs), the only known truly endothelial EPC subset. Studies from our group showed that the Ca²⁺ toolkit differs between peripheral blood- and umbilical cord blood (UCB)-derived ECFCs. In the present article, we first discuss how VEGF uses repetitive Ca²⁺ spikes to regulate angiogenesis in ECFCs and outline how VEGF-induced intracellular Ca²⁺ oscillations differ between the two ECFC subtypes. We then hypothesize about the possibility to rejuvenate the biological activity of autologous ECFCs by transfecting the cell with the Ca²⁺ -permeable channel Transient Receptor Potential Canonical 3, which selectively drives the Ca²⁺ response to VEGF in UCB-derived ECFCs.

Kinetics of plasma von Willebrand factor in acute myocardial infarction patients: a meta-analysis

Previous studies have shown a variation in plasma level of von Willebrand factor (vWF) in acute myocardial infarction (AMI) patients but with contentious results. In this study, we performed a meta-analysis to evaluate the kinetics of plasma vWF after AMI. A total of 11 qualified studies were obtained through systematical search in PubMed, Web of science, Cochrane Library database and CNKI, followed by search of reference lists, involving 519 AMI patients and 466 non-AMI controls. The standard mean difference (SMD) and 95% confidence intervals (95% CI) were calculated using random-effects model. Results indicated that the plasma vWF was significantly increased in the first several hours after onset of AMI (SMD = 1.94, 95% CI = 1.39-2.48, P < 0.001) and stayed at high level until 24 h (SMD = 1.17, 95% CI = 0.45-1.89, P = 0.001). Elevated level of vWF appeared to persist for one week and reduced to normal until the fourteenth day after AMI (SMD = 0.44, 95% CI = -0.14-1.02, P = 0.14). Subgroup analysis revealed that the high level of vWF lasted just for 1 day in patients with a symptom duration ≤ 6 h before admission. For patients with a symptom duration > 6 h, elevated vWF was found in all 7 days except day 1. Our findings determined the kinetics of plasma vWF after AMI, and might provide a new insight in monitoring AMI progression.

Beneficial Effects of Reconstituted High-Density Lipoprotein (rHDL) on Circulating CD34+ Cells in Patients after an Acute Coronary Syndrome

Background

High-density lipoproteins (HDL) favorably affect endothelial progenitor cells (EPC). Circulating progenitor cell level and function are impaired in patients with acute coronary syndrome (ACS). This study investigates the short-term effects of reconstituted HDL (rHDL) on circulating progenitor cells in patients with ACS.

Methods and Findings

The study population consisted of 33 patients with recent ACS: 20 patients from the ERASE trial (randomized to receive 4 weekly intravenous infusions of CSL-111 40 mg/kg or placebo) and 13 additional patients recruited as controls using the same enrolment criteria. Blood was collected from 16 rHDL (CSL-111)-treated patients and 17 controls at baseline and at 6–7 weeks (i.e. 2–3 weeks after the fourth infusion of CSL-111 in ERASE). CD34⁺ and CD34⁺/kinase insert domain receptor (KDR⁺) progenitor cell counts were analyzed by flow cytometry. We found preserved CD34⁺ cell counts in CSL-111-treated subjects at follow-up (change of 1.6%), while the number of CD34⁺ cells was reduced (-32.9%) in controls (p = 0.017 between groups). The level of circulating SDF-1 (stromal cell-derived factor-1), a chemokine involved in progenitor cell recruitment, increased significantly (change of 21.5%) in controls, while it remained unchanged in CSL-111-treated patients (p = 0.031 between groups). In vitro exposure to CSL-111 of early EPC isolated from healthy volunteers significantly increased CD34⁺ cells, reduced early EPC apoptosis and enhanced their migration capacity towards SDF-1.

Conclusions

The relative increase in circulating CD34⁺ cells and the low SDF-1 levels observed following rHDL infusions in ACS patients point towards a role of rHDL in cardiovascular repair mechanisms.

Endothelial damage in major depression patients is modulated by SSRI treatment, as demonstrated by circulating biomarkers and an in vitro cell model

There is a link between depression, cardiovascular events and inflammation. We have explored this connection through endothelial dysfunction, using in vivo and in vitro approaches. We evaluated circulating biomarkers of endothelial dysfunction in patients with major depression at their diagnosis (MD-0) and during antidepressant treatment with the selective serotonin reuptake inhibitor escitalopram, for 8 and 24 weeks (MD-8 and MD-24). Results were always compared with matched healthy controls (CON). We measured in vivo circulating endothelial cells (CECs) and endothelial progenitor cells (EPCs) in blood samples, and assessed plasma levels of soluble von Willebrand factor (VWF) and vascular cell adhesion molecule-1 (VCAM-1). CEC counts, soluble VWF and VCAM-1 were statistically elevated in MD-0 (P<0.01 versus CON) and gradually decreased during treatment. Conversely, EPC levels were lower in MD-0, tending to increase throughout treatment. In vitro studies were performed in human endothelial cells cultured in the presence of sera from each study group. Elevated expression of the inflammation marker intercellular adhesion molecule-1 and oxidative stress, with lower presence of endothelial nitric oxide synthase and higher reactive oxygen species production, were found in cells exposed to MD-0 sera (P<0.05 versus CON). These results were normalized in cells exposed to MD-24 sera. Thrombogenicity of extracellular matrices generated by these cells, measured as expression of VWF, tissue factor and platelet reactivity, showed non-significant differences. We provide a model of cultured endothelial cells reproducing endothelial dysfunction in naive patients with major depression, demonstrating endothelial damage and inflammation at diagnosis, and recovering with selective serotonin reuptake inhibitor treatment for 24 weeks.

The role of endothelial progenitor cells in transient ischemic attack patients for future cerebrovascular events

Background:

The role of endothelial progenitor cells (EPCs) in the maintenance of vascularization following ischemic brain after experimental stroke has been established. Accordingly, in this study, we evaluated the role of circulating EPCs in transient ischemic attack (TIA) patients for future cerebrovascular (CV) events.

Materials and Methods:

The level of circulating EPCs (staining markers: CD34, CD309) were determined using flow cytometry at 24 h after TIA in thirty consecutive patients. The EPCs level was also evaluated once in thirty healthy volunteers. Over a period of 12 months, all patients were evaluated by an experienced neurologist for recurrent TIA, stroke or death induced by CV disorders.

Results:

Circulating EPCs increased in patients group following the first attack of TIA when compared with controls. By analysis of covariance, cardiovascular event history, hyperlipidemia, and statin therapy remained significant independent predictors of EPCs. The mean (standard deviation) duration of follow-up was 10.5 (3.1) months (range, 2–12 months). During follow-up, a total of three patients died due to CV accident and four patients experienced again recurrent TIA. By analyzing data with Cox regression, EPC did not predict the future CV events in TIA patients.

Conclusion:

Increased incidence of future CV events did not occur in those patients with elevated EPCs in the first attack of TIA. The significant predicting factors of EPCs were cardiovascular event history, hyperlipidemia, and statin therapy.

Endothelial Progenitor Cells Predict Cardiovascular Events after Atherothrombotic Stroke and Acute Myocardial Infarction. A PROCELL Substudy

Introduction

The aim of this study was to determine prognostic factors for the risk of new vascular events during the first 6 months after acute myocardial infarction (AMI) or atherothrombotic stroke (AS). We were interested in the prognostic role of endothelial progenitor cells (EPC) and circulating endothelial cells (CEC)

Methods

Between February 2009 and July 2012, 100 AMI and 50 AS patients were consecutively studied in three Spanish centres. Patients with previously documented coronary artery disease or ischemic strokes were excluded. Samples were collected within 24h of onset of symptoms. EPC and CEC were studied using flow cytometry and categorized by quartiles. Patients were followed for up to 6 months. NVE was defined as new acute coronary syndrome, transient ischemic attack (TIA), stroke, or any hospitalization or death from cardiovascular causes. The variables included in the analysis included: vascular risk factors, carotid intima-media thickness (IMT), atherosclerotic burden and basal EPC and CEC count. Multivariate survival analysis was performed using Cox regression analysis.

Results

During follow-up, 19 patients (12.66%) had a new vascular event (5 strokes; 3 TIAs; 4 AMI; 6 hospitalizations; 1 death). Vascular events were associated with age (P = 0.039), carotid IMT≥0.9 (P = 0.044), and EPC count (P = 0.041) in the univariate analysis. Multivariate Cox regression analysis showed an independent association with EPC in the lowest quartile (HR: 10.33, 95%CI (1.22–87.34), P = 0.032] and IMT≥0.9 [HR: 4.12, 95%CI (1.21–13.95), P = 0.023].

Conclusions

Basal EPC and IMT≥0.9 can predict future vascular events in patients with AMI and AS, but CEC count does not affect cardiovascular risk.

Activation of the Neuroprotective Angiotensin-Converting Enzyme 2 in Rat Ischemic Stroke

The angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas axis represents a promising target for inducing stroke neuroprotection. Here, we explored stroke-induced changes in expression and activity of endogenous angiotensin-converting enzyme 2 and other system components in Sprague-Dawley rats. To evaluate the clinical feasibility of treatments that target this axis and that may act in synergy with stroke-induced changes, we also tested the neuroprotective effects of diminazene aceturate, an angiotensin-converting enzyme 2 activator, administered systemically post stroke. Among rats that underwent experimental endothelin-1-induced ischemic stroke, angiotensin-converting enzyme 2 activity in the cerebral cortex and striatum increased in the 24 hours after stroke. Serum angiotensin-converting enzyme 2 activity was decreased within 4 hours post stroke, but rebounded to reach higher than baseline levels 3 days post stroke. Treatment after stroke with systemically applied diminazene resulted in decreased infarct volume and improved neurological function without apparent increases in cerebral blood flow. Central infusion of A-779, a Mas receptor antagonist, resulted in larger infarct volumes in diminazene-treated rats, and central infusion of the angiotensin-converting enzyme 2 inhibitor MLN-4760 alone worsened neurological function. The dynamic alterations of the protective angiotensin-converting enzyme 2 pathway after stroke suggest that it may be a favorable therapeutic target. Indeed, significant neuroprotection resulted from poststroke angiotensin-converting enzyme 2 activation, likely via Mas signaling in a blood flow-independent manner. Our findings suggest that stroke therapeutics that target the angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas axis may interact cooperatively with endogenous stroke-induced changes, lending promise to their further study as neuroprotective agents.