Endothelial progenitor cells dysfunction and impaired tissue reparation: The missed link in diabetes mellitus development

The Impact of Modern Anti-Diabetic Treatment on Endothelial Progenitor Cells

Diabetes is one of the leading chronic diseases globally with a significant impact on mortality. This condition is associated with chronic microvascular and macrovascular complications caused by vascular damage. Recently, endothelial progenitor cells (EPCs) raised interest due to their regenerative properties. EPCs are mononuclear cells that are derived from different tissues. Circulating EPCs contribute to regenerating the vessel's intima and restoring vascular function. The ability of EPCs to repair vascular damage depends on their number and functionality. Diabetic patients have a decreased circulating EPC count and impaired EPC function. This may at least partially explain the increased risk of diabetic complications, including the increased cardiovascular risk in these patients. Recent studies have confirmed that many currently available drugs with proven cardiovascular benefits have beneficial effects on EPC count and function. Among these drugs are also medications used to treat different types of diabetes. This manuscript aims to critically review currently available evidence about the ways anti-diabetic treatment affects EPC biology and to provide a broader context considering cardiovascular complications. The therapies that will be discussed include lifestyle adjustments, metformin, sulphonylureas, gut glucosidase inhibitors, thiazolidinediones, dipeptidyl peptidase 4 inhibitors, glucagon-like peptide 1 receptor analogs, sodium-glucose transporter 2 inhibitors, and insulin.

The Role of Endothelial Progenitor Cells in Atherosclerosis and Impact of Anti-Lipemic Treatments on Endothelial Repair

Cardiovascular complications are associated with advanced atherosclerosis. Although atherosclerosis is still regarded as an incurable disease, at least in its more advanced stages, the discovery of endothelial progenitor cells (EPCs), with their ability to replace old and injured cells and differentiate into healthy and functional mature endothelial cells, has shifted our view of atherosclerosis as an incurable disease, and merged traditional theories of atherosclerosis pathogenesis with evolving concepts of vascular biology. EPC alterations are involved in the pathogenesis of vascular abnormalities in atherosclerosis, but many questions remain unanswered. Many currently available drugs that impact cardiovascular morbidity and mortality have shown a positive effect on EPC biology. This review examines the role of endothelial progenitor cells in atherosclerosis development, and the impact standard antilipemic drugs, including statins, fibrates, and ezetimibe, as well as more novel treatments such as proprotein convertase subtilisin/kexin type 9 (PCSK9) modulating agents and angiopoietin-like proteins (Angtpl3) inhibitors have on EPC biology.

Up-regulation of GLP-1R improved the dysfunction of late EPCs under hyperglycemia by regulating SIRT1 expression

The dysfunction of endothelial progenitor cells (EPCs) is closely associated with diabetic vascular complications. Both glucagonlike peptide-1 receptor (GLP-1R) and silent information regulator 1 (SIRT1) can control systemic glucose homeostasis and protect endothelial cells against hyperglycemia-induced oxidative stress. In this study, we mainly assessed the role played by SIRT1 and GLP-1R and their relationship in regulating the function of late EPCs under hyperglycemia stimulation. Human peripheral blood mononuclear cells (PBMCs) were cultured in EGM-2 medium and induced to differentiate into EPCs and 25 mM glucose was used to stimulate EPCs to obtain a hyperglycemia condition. Subsequently, the expression and location of GLP-1R and SIRT1 in EPCs were detected. After GLP-1R or SIRT1 knockdown, or the treatment by GLP-1R agonist and/or SIRT1 agonist/inhibitor, the effects of SIRT1 and GLP-1R and their relationship in regulating the function of late EPCs under hyperglycemia stimulation was studied by detecting the apoptosis, migration, adhesion and angiogenicity abilities of EPCs. Results demonstrated that, in high-glucose stimulated EPCs, the expression of GLP-1R and SIRT1 was down-regulated. The knockdown of either GLP-1R or SIRT1 could increase EPCs apoptosis and weaken the migration, adhesion and angiogenicity abilities of EPCs. In addition, the improvement effects of Exendin-4 or GLP-1R over-expression on EPCs dysfunction could be weakened to some degree under SIRT1 knockdown. In conclusion, both GLP-1R and SIRT1 expression played important roles in regulating EPCs dysfunction under hyperglycemia and the up-regulation of GLP-1R improved the dysfunction of late EPCs by regulating SIRT1 expression.

Differences of Angiogenesis Factors in Tumor and Diabetes Mellitus

Angiogenesis, as a process occurring under the regulation of a variety of factors, is one of the important ways of vascular development. It coexists in a variety of pathological and physiological processes. Now a large number of studies have proved that tumor growth, metastasis, and various vascular complications of diabetes are closely related to angiogenesis, and an increasing number of studies have shown that there are many common factors between the two. But angiogenesis is the opposite of the two: it is enhanced in tumors and suppressed in diabetes. Therefore, this review discusses the causes of the phenomenon from the expression of various factors affecting angiogenesis in these two diseases and their effects on angiogenesis in the relevant microenvironment, as well as the application status of these factors or cells as therapeutic targets in the treatment of these two diseases.

Exendin-4 reverses high glucose-induced endothelial progenitor cell dysfunction via SDF-1β/CXCR7-AMPK/p38-MAPK/IL-6 axis

AIM

Exendin-4, a glucagon-like peptide-1 (GLP-1) analog, has been used for treating diabetes mellitus (DM). However, its effects on improving the dysfunction of high glucose (HG)-induced endothelial progenitor cells (EPCs) remain unclear. The present study explored the effects of Exendin-4 on improving dysfunction of EPCs and the underlying mechanism.

METHODS

EPCs were isolated from SD rats and identified by flow cytometry. Next, the EPCs were treated by HG and high or low concentration of Exendin-4, and cell viability, migration and tube formation were, respectively, examined by performing MTT assay, wound-healing assay and tube formation assay. Interleukin-6 (IL-6) secretion was measured by enzyme-linked immunosorbent assay (ELISA). The protein expressions of relative stromal-derived growth factor-1β (SDF-1β), C-X-C chemokine receptor type 7 (CXCR7), AMP-activated protein kinase (AMPK), p38 and expressions of CXCR7 and IL-6 in EPCs were measured by Western blot. The cell behaviors of EPCs treated by HG and Exendin-4 with or without silencing of CXCR7 and IL-6 were detected.

RESULTS

Exendin-4 reversed the inhibitory effects of HG on viability, migration and tube formation of EPCs and on SDF-1β/CXCR7-AMPK pathway in EPCs in a dose-dependent manner. Moreover, Exendin-4 promoted the effects of HG on IL-6 level in EPCs through the promotion of p38-MAPK phosphorylation and reduction of cleaved caspase-3 protein expressions in EPCs. However, silencing of CXCR7 and IL-6 reversed the effects of Exendin-4 on cell behaviors, inactivated SDF-1β/CXCR7-AMPK pathway and increased cleaved caspase-3 expression in EPCs.

CONCLUSIONS

Exendin-4 could ameliorate HG-induced EPC dysfunction through regulating the production of IL-6 via SDF-1β/CXCR7-AMPK/p38-MAPK axis.

Exendin-4 regulates endoplasmic reticulum stress to protect endothelial progenitor cells from high-glucose damage

BACKGROUND

High glucose affects the function of endothelial cells by increasing oxidative stress. Studies have found that exendin-4 can improve wound healing in diabetic mice and mice with normal blood glucose. However, the mechanism of exendin-4 in endothelial progenitor cells under high-glucose condition has not been fully elucidated.

METHODS

Diabetic mouse models were established to investigate the effects of exendin-4 on endothelial progenitor cells in diabetic mice. Serum superoxide dismutase (SOD) and malondialdehyde (MDA) were determined by WST-8 and thiobarbituric acid (TBA) colorimetry, respectively. Cell viability, apoptosis and reactive oxygen species (ROS) were detected by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and flow cytometry. Gene and protein expressions were determined by Quantitative reverse transcription PCR (qRT-PCR) assay and Western blot (WB).

RESULTS

The results showed that in diabetic mice, exendin-4 did not affect blood glucose or body weight, moreover, it improved aortic diastolic function, increased SOD activity and down-regulated malondialdehyde (MDA) level in the mice. In addition, exendin-4 also increased endothelial progenitor cell (EPCs) viability and reduced cell apoptosis through inhibiting p38 MAPK pathway and reducing endoplasmic reticulum stress and ROS.

CONCLUSION

Exndin-4 can alleviate diabetes-caused damage to mice, moreover, it reduced endoplasmic reticulum stress and ROS through inhibiting p38 MAPK pathway in MPCs cells under high-glucose condition, thus increasing cell viability and reducing cell apoptosis.

Altered signature of apoptotic endothelial cell-derived microvesicles predicts chronic heart failure phenotypes

Aim: to evaluate the associations between signatures of apoptotic endothelial cell-derived microvesicles (MVs) with phenotypes of chronic heart failure (HF). Methods: The study cohort consisted of 388 prospectively involved subjects with HF patients with predominantly reduced left ventricular ejection fraction (HFrEF), HF with preserved ejection fraction (HFpEF) and HF with mid-range ejection fraction (HFmrEF). All biomarkers were measured at baseline. Results: The number of circulating CD31+/annexin V+ MVs in HFrEF and HFmrEF patients was similar. The number of circulating CD144+/annexin V+ MVs in HFrEF patients was significantly higher than HFmrEF and HFpEF. We determined that a combination of number of circulating CD31+/annexin V+ MVs and Gal-3 was the best predictor of HFpEF and that number of circulating CD144+/annexin V+ MVs is able to increase predictive capabilities of soluble ST2 (sST2) and Gal-3 for HFrEF. Conclusion: We found that the number of circulating CD31+/annexin V+ MVs may improve a predictive capacity for conventional HF biomarkers.

Ameliorating Methylglyoxal-Induced Progenitor Cell Dysfunction for Tissue Repair in Diabetes

Patient-derived progenitor cell (PC) dysfunction is severely impaired in diabetes, but the molecular triggers that contribute to mechanisms of PC dysfunction are not fully understood. Methylglyoxal (MGO) is one of the highly reactive dicarbonyl species formed during hyperglycemia. We hypothesized that the MGO scavenger glyoxalase 1 (GLO1) reverses bone marrow-derived PC (BMPC) dysfunction through augmenting the activity of an important endoplasmic reticulum stress sensor, inositol-requiring enzyme 1α (IRE1α), resulting in improved diabetic wound healing. BMPCs were isolated from adult male db/db type 2 diabetic mice and their healthy corresponding control db/+ mice. MGO at the concentration of 10 µmol/L induced immediate and severe BMPC dysfunction, including impaired network formation, migration, and proliferation and increased apoptosis, which were rescued by adenovirus-mediated GLO1 overexpression. IRE1α expression and activation in BMPCs were significantly attenuated by MGO exposure but rescued by GLO1 overexpression. MGO can diminish IRE1α RNase activity by directly binding to IRE1α in vitro. In a diabetic mouse cutaneous wound model in vivo, cell therapies using diabetic cells with GLO1 overexpression remarkably accelerated wound closure by enhancing angiogenesis compared with diabetic control cell therapy. Augmenting tissue GLO1 expression by adenovirus-mediated gene transfer or with the small-molecule inducer trans-resveratrol and hesperetin formulation also improved wound closure and angiogenesis in diabetic mice. In conclusion, our data suggest that GLO1 rescues BMPC dysfunction and facilitates wound healing in diabetic animals, at least partly through preventing MGO-induced impairment of IRE1α expression and activity. Our results provide important knowledge for the development of novel therapeutic approaches targeting MGO to improve PC-mediated angiogenesis and tissue repair in diabetes.

Potential role of Peroxisome Proliferator Activated Receptor gamma analogues in regulation of endothelial progenitor cells in diabetes mellitus: An overview

Endothelial progenitor cells are recognized as the potential targets for the revascularization and angiogenesis because of their ability to get themselves transformed into mature endothelial cells. Underlying pathophysiology in diabetes mellitus leads to decrease in circulatory endothelial progenitor cells, resulting in diabetic macro-vascular and micro-vascular complications. Peroxisome Proliferator Activated Receptor (PPAR) gamma analogues serves as an effective therapy for controlling blood sugar levels and preventing its complications. Reports of clinical trials and meta-analysis of clinical trial suggests the beneficial aspects of PPAR gamma therapy in increasing the number and function of circulating endothelial progenitor cells. This review highlights the pleotropic effect of PPAR gamma analogs, apart from their antidiabetic action via reduction of oxidative stress, increasing expression of eNOS, reducing level of miR 22, miR 222 levels and positive modulation of rapamycin/Protein kinase B/phosphoinoside3-kinase pathways, preventing the early apoptosis, enhanced mobility proliferation and transformation into mature endothelial cells. PPAR gamma therapy in diabetes regulates endothelial progenitor cells, reduces complications of diabetes like retinopathy, nephropathy, neuropathy, cardiomyopathy, deep vein thrombosis, and maintains the healthy vasculature.

Attenuated endothelial function is associated with decreased endothelial progenitor cells and nitric oxide in premenopausal diabetic women

Previous studies have demonstrated that the deleterious effect of diabetes mellitus (DM) on the risk of cardiovascular disease also occurs in premenopausal women, in spite of their relatively high estrogen levels; however, the underlying mechanism remains unclear. The present study aimed to investigate the sex‑related differences in circulating endothelial progenitor cells (EPCs) in a relatively young population with type 2 DM (T2DM) and its underlying mechanism. The number and functional activity of circulating EPCs, and vascular endothelial function assessed using flow‑mediated dilation (FMD), were compared in premenopausal women and age‑matched men with or without T2DM. Nitric oxide (NO) in the plasma or NO secreted by EPCs was also measured. The number and activity of circulating EPCs, and NO levels in the plasma or culture medium, were lower in premenopausal women with T2DM compared with those without T2DM. In addition, the number and activity of circulating EPCs and NO levels were decreased in men with T2DM compared with in age‑matched premenopausal women with T2DM. FMD was positively correlated with the number and activity of circulating EPCs, and NO levels. In conclusion, DM in premenopausal women may significantly impair the repair capability of EPCs and lead to endothelial dysfunction, which may be associated with reduced NO production. In patients with both DM and normal glucose tolerance, sex‑related differences of EPCs are presented in a young population.

Endothelial Progenitor Cells: New Targets for Therapeutics for Inflammatory Conditions With High Cardiovascular Risk

Over the past decade, we have witnessed an exponential growth of interest into the role of endothelial progenitor cells (EPCs) in cardiovascular disease. While the major thinking revolves around EPC angiogenic repair properties, we have used a hypothesis-driven approach to discover disease-related defects in their characteristics and based on these findings, have identified opportunities for functional enhancement, which offer an exciting avenue for translation into clinical intervention. In this review, we focus on two groups; circulating myeloid angiogenic cells (MACs) and late outgrowth endothelial colony forming cells (ECFCs), and will discuss the unique properties and defects of each population, as new insights have been gained into the potential function of each sub-type using current techniques and multiomic technology. We will discuss their role in inflammatory disorders and alterations in mitochondrial function. In addition, we share key insights into the glycocalyx, and propose this network of membrane-bound proteoglycans and glycoproteins, covering the endothelium warrants further investigation in order to clarify its significance in ECFC regulation of vascularization and angiogenesis and ultimately for potential translational therapeutic aspects.

iPSCs-based generation of vascular cells: reprogramming approaches and applications

Recent advances in the field of induced pluripotent stem cells (iPSCs) research have opened a new avenue for stem cell-based generation of vascular cells. Based on their growth and differentiation potential, human iPSCs constitute a well-characterized, generally unlimited cell source for the mass generation of lineage- and patient-specific vascular cells without any ethical concerns. Human iPSCs-derived vascular cells are perfectly suited for vascular disease modeling studies because patient-derived iPSCs possess the disease-causing mutation, which might be decisive for full expression of the disease phenotype. The application of vascular cells for autologous cell replacement therapy or vascular engineering derived from immune-compatible iPSCs possesses huge clinical potential, but the large-scale production of vascular-specific lineages for regenerative cell therapies depends on well-defined, highly reproducible culture and differentiation conditions. This review will focus on the different strategies to derive vascular cells from human iPSCs and their applications in regenerative therapy, disease modeling and drug discovery approaches.

Reduced mRNA and Protein Expression Levels of Tet Methylcytosine Dioxygenase 3 in Endothelial Progenitor Cells of Patients of Type 2 Diabetes With Peripheral Artery Disease

Endothelial progenitor cells (EPCs) with immunological properties repair microvasculature to prevent the complications in patients with diabetes. Epigenetic changes such as DNA methylation alter the functions of cells. Tet methylcytosine dioxygenases (TETs) are enzymes responsible for the demethylation of cytosine on genomic DNA in cells. We hypothesized that EPCs of diabetic patients with peripheral artery disease (D-PAD) might have altered expression levels of TETs. Subjects who were non-diabetic (ND, n = 22), with diabetes only (D, n = 29) and with D-PAD (n = 22) were recruited for the collection of EPCs, which were isolated and subjected to analysis. The mRNA and protein expression levels of TET1, TET2, and TET3 were determined using real-time PCR and immunoblot, respectively. The TET1 mRNA expression level in ND group was lower than that in the D and D-PAD groups. The TET3 mRNA level in the ND group was higher than that in the D group, which was higher than that in the D-PAD group. The TET1 protein level in the D-PAD group, but not the D group, was higher than that in the ND group. The TET2 protein level in the D-PAD group, but not the D group, was lower than that in the ND group. The TET3 protein level in the ND group was higher than that in the D group, which was higher than that in the D-PAD group, which is the lowest among the three groups. The changes of TETs protein levels were due to the alterations of their transcripts. These probably lead to epigenetic changes, which may be responsible for the reductions of EPCs numbers and functions in patients with the D-PAD. The expression pattern of TET3 mRNA and TET3 protein in EPCs may be a biomarker of angiopathy in diabetic patients.

MiR-27b augments bone marrow progenitor cell survival via suppressing the mitochondrial apoptotic pathway in Type 2 diabetes

Bone marrow-derived progenitor cells (BMPCs) are potential candidates for autologous cell therapy in tissue repair and regeneration because of their high angiogenic potential. However, increased progenitor cell apoptosis in diabetes directly limits their success in the clinic. MicroRNAs are endogenous noncoding RNAs that regulate gene expression at the posttranscriptional level, but their roles in BMPC-mediated angiogenesis are incompletely understood. In the present study, we tested the hypothesis that the proangiogenic miR-27b inhibits BMPC apoptosis in Type 2 diabetes. 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 after 24 h of exposure to methylglyoxal (MGO) or oxidized low-density lipoprotein but not high glucose, advanced glycation end products, the reactive oxygen species generator LY83583, or H2O2 The increase in BMPC apoptosis in the diabetic mice was rescued following transfection with a miR-27b mimic, and the increased apoptosis induced by MGO was also rescued by the miR-27b mimic. p53 protein expression and the Bax/Bcl-2 ratio in EPCs (Western blot analyses) were significantly higher in db/db mice, both of which were suppressed by miR-27b. Furthermore, mitochondrial respiration, as measured by oxygen consumption rate, was enhanced by miR-27b in diabetic BMPCs, with concomitant decrease of mitochondrial Bax/Bcl-2 ratio. The 3' UTR binding assays revealed that both Bax, and its activator RUNX1, were direct targets of miR-27b, suggesting that miR-27b inhibits Bax expression in both direct and indirect manners. miR-27b prevents EPC apoptosis in Type 2 diabetic mice, at least in part, by suppressing p53 and the Bax/Bcl-2 ratio. These findings may provide a mechanistic basis for rescuing BMPC dysfunction in diabetes for successful autologous cell therapy.