Generalised reduction of putative endothelial progenitors and CXCR4-positive peripheral blood cells in type 2 diabetes

GLP-1RA therapy increases circulating vascular regenerative cell content in people living with type 2 diabetes

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 (SGLT2) inhibitors are guideline-recommended therapies for the management of type 2 diabetes (T2D), atherosclerotic cardiovascular disease, heart failure, and chronic kidney disease. We previously observed in people living with T2D and coronary artery disease that circulating vascular regenerative (VR) progenitor cell content increased following 6-mo use of the SGLT2 inhibitor empagliflozin. In this post hoc subanalysis of the ORIGINS-RCE CardioLink-13 study (ClinicalTrials.gov Identifier NCT05253521), we analyzed the circulating VR progenitor cell content of 92 individuals living with T2D, among whom 20 were on a GLP-1RA, 42 were on an SGLT2 inhibitor but not a GLP-1RA, and 30 were on neither of these vascular protective therapies. In the GLP-1RA group, the mean absolute count of circulating VR progenitor cells defined by high aldehyde dehydrogenase (ALDH) activity (ALDHhiSSClow) and VR progenitor cells further characterized by surface expression of the proangiogenic marker CD133 (ALDHhiSSClowCD133+) was higher than the group receiving neither a GLP-1RA nor an SGLT2 inhibitor (P = 0.02) and comparable with that in the SGLT2 inhibitor group (P = 0.25). The absolute count of proinflammatory, granulocyte-restricted precursor cells (ALDHhiSSChi) was significantly lower in the GLP-1RA group compared with the group on neither therapy (P = 0.031). Augmented vessel repair initiated by VR cells with previously documented proangiogenic activity, alongside a reduction in systemic, granulocyte precursor-driven inflammation, may represent novel mechanisms responsible for the cardiovascular-metabolic benefits of GLP-1RA therapy. Prospective, randomized clinical trials are now warranted to establish the value of recovering circulating VR progenitor cell content with blood vessel regenerative functions.NEW & NOTEWORTHY In this post hoc subanalysis of 92 individuals living with T2D and at high cardiovascular risk, the authors summarize the differences in circulating vascular regenerative (VR) progenitor cell content between those on GLP-1RA therapy, on SGLT2 inhibitor without GLP-1RA therapy, and on neither therapy. Those on GLP-1RA therapy demonstrated greater circulating VR progenitor cell content and reduced proinflammatory granulocyte precursor content. These results offer novel mechanistic insights into the cardiometabolic benefits associated with GLP-1RA therapy.

Association of vitamin D and bisphenol A levels with cardiovascular risk in an elderly Italian population: results from the InCHIANTI study

Few studies have evaluated the association between circulating levels of 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D), and the endocrine disruptor bisphenol A (BPA), with risk of cardiovascular (CV) disease in elderly individuals. This was a cross-sectional study in a subgroup of elderly people from the InCHIANTI Biobank in Italy. We examined the association between circulating serum vitamin D metabolites, 1,25(OH)2D, 25(OH)D, and the endocrine disrupting agent BPA, with an arbitrary CV risk score and the European Society of Cardiology-based 10-year CV risk (SCORE2/SCORE2-OP) using univariate and multiple regression. In 299 individuals, blood samples were tested for serum values of 25(OH)D, 1,25(OH)2D and urinary BPA levels. One hundred eighty individuals (60.2%) were deficient (< 20 ng/ml) in 25(OH)D. Levels of 25(OH)D and 1,25(OH)2D were negatively correlated with CV risk score (p < 0.0001 for both) as well as SCORE2/SCORE2-OP (p < 0.0001 for both) while BPA levels were positively correlated with both CV risk scores (p < 0.0001 for both). In a logistic regression model, male gender (odds ratio; OR: 2.1, 95% CI:1.1-3.8, p = 0.022), obesity (OR:2.8, 95% CI:1.2-6.5, p = 0.016) and BPA levels ≥ 110 ng/dl (OR:20.9, 95% CI:9.4-46.8, p < 0.0001) were associated with deficient levels of 25(OH)D. 1,25(OH)2D levels < 41 ng/dl and 25(OH)D levels < 20 ng/ml were associated with CV risk score ≥ 3 (OR: 4.16, 95% CI: 2.32-7.4, p < 0.0001 and OR: 1.86, 95% CI: 1.02-3.39, p = 0.044) respectively and 1,25(OH)2D levels < 41 ng/dl were associated with SCORE2/SCORE2-OP of ≥ 20% (OR:2.98, 95% CI: 1.7-5.2, p = 0.0001). In this cross-sectional analysis, BPA exposure was associated with significantly reduced levels of vitamin D that in turn were significantly associated with increased CV risk.

Human Cord Blood Endothelial Progenitor Cells and Pregnancy Complications (Preeclampsia, Gestational Diabetes Mellitus, and Fetal Growth Restriction)

Hemangioblasts give rise to endothelial progenitor cells (EPCs), which also express the cell surface markers CD133 and c-kit. They may differentiate into the outgrowth endothelial cells (OECs) that control neovascularization in the developing embryo. According to numerous studies, reduced levels of EPCs in circulation have been linked to human cardiovascular disorders. Furthermore, preeclampsia and senescence have been linked to levels of EPCs produced from cord blood. Uncertainties surround how preeclampsia affects the way EPCs function. It is reasonable to speculate that preeclampsia may have an impact on the function of fetal EPCs during the in utero period; however, the present literature suggests that maternal vasculopathies, including preeclampsia, damage fetal circulation. Additionally, the differentiation potential and general activity of EPCs may serve as an indicator of the health of the fetal vascular system as they promote neovascularization and repair during pregnancy. Thus, the purpose of this review is to compare-through the assessment of their quantity, differentiation potency, angiogenic activity, and senescence-the angiogenic function of fetal EPCs obtained from cord blood for normal and pregnancy problems (preeclampsia, gestational diabetes mellitus, and fetal growth restriction). This will shed light on the relationship between the angiogenic function of fetal EPCs and pregnancy complications, which could have an effect on the management of long-term health issues like metabolic and cardiovascular disorders in offspring with abnormal vasculature development.

Endothelial progenitor cells as biomarkers of diabetes-related cardiovascular complications

Diabetes mellitus (DM) constitutes a chronic metabolic disease characterized by elevated levels of blood glucose which can also lead to the so-called diabetic vascular complications (DVCs), responsible for most of the morbidity, hospitalizations and death registered in these patients. Currently, different approaches to prevent or reduce DM and its DVCs have focused on reducing blood sugar levels, cholesterol management or even changes in lifestyle habits. However, even the strictest glycaemic control strategies are not always sufficient to prevent the development of DVCs, which reflects the need to identify reliable biomarkers capable of predicting further vascular complications in diabetic patients. Endothelial progenitor cells (EPCs), widely known for their potential applications in cell therapy due to their regenerative properties, may be used as differential markers in DVCs, considering that the number and functionality of these cells are affected under the pathological environments related to DM. Besides, drugs commonly used with DM patients may influence the level or behaviour of EPCs as a pleiotropic effect that could finally be decisive in the prognosis of the disease. In the current review, we have analysed the relationship between diabetes and DVCs, focusing on the potential use of EPCs as biomarkers of diabetes progression towards the development of major vascular complications. Moreover, the effects of different drugs on the number and function of EPCs have been also addressed.

Bone marrow vasculature advanced in vitro models for cancer and cardiovascular research

Cardiometabolic diseases and cancer are among the most common diseases worldwide and are a serious concern to the healthcare system. These conditions, apparently distant, share common molecular and cellular determinants, that can represent targets for preventive and therapeutic approaches. The bone marrow plays an important role in this context as it is the main source of cells involved in cardiovascular regeneration, and one of the main sites of liquid and solid tumor metastasis, both characterized by the cellular trafficking across the bone marrow vasculature. The bone marrow vasculature has been widely studied in animal models, however, it is clear the need for human-specific in vitro models, that resemble the bone vasculature lined by endothelial cells to study the molecular mechanisms governing cell trafficking. In this review, we summarized the current knowledge on in vitro models of bone marrow vasculature developed for cardiovascular and cancer research.

Liraglutide preserves CD34+ stem cells from dysfunction Induced by high glucose exposure

Background

Glucagon like peptide-1 receptor agonists (GLP-1RAs) have shown to reduce mortality and cardiovascular events in patients with type 2 diabetes mellitus (T2DM). Since the impairment in number and function of vasculotrophic circulating CD34⁺ hematopoietic stem progenitor cells (HSPCs) in T2D has been reported to increase cardiovascular (CV) risk, we hypothesized that one of the mechanisms whereby GLP-1 RAs exert CV protective effects may be related to the ability to improve CD34⁺ HSPC function.

Methods

In cord blood (CB)-derived CD34⁺ HSPC, the expression of GLP-1 receptor (GLP-1R) mRNA, receptor protein and intracellular signaling was evaluated by RT-qPCR and Western Blot respectively. CD34⁺ HSPCs were exposed to high glucose (HG) condition and GLP-1RA liraglutide (LIRA) was added before as well as after functional impairment. Proliferation, CXCR4/SDF-1α axis activity and intracellular ROS production of CD34⁺ HSPC were evaluated.

Results

CD34⁺ HSPCs express GLP-1R at transcriptional and protein level. LIRA treatment prevented and rescued HSPC proliferation, CXCR4/SDF-1α axis activity and metabolic imbalance from HG-induced impairment. LIRA stimulation promoted intracellular cAMP accumulation as well as ERK1/2 and AKT signaling activation. The selective GLP-1R antagonist exendin (9–39) abrogated LIRA-dependent ERK1/2 and AKT phosphorylation along with the related protective effects.

Conclusion

We provided the first evidence that CD34⁺ HSPC express GLP-1R and that LIRA can favorably impact on cell dysfunction due to HG exposure. These findings open new perspectives on the favorable CV effects of GLP-1 RAs in T2DM patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01486-9.

Beneficial Role of Vitamin D on Endothelial Progenitor Cells (EPCs) in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death in the world. Endothelial progenitor cells (EPCs) are currently being explored in the context of CVD risk. EPCs are bone marrow derived progenitor cells involved in postnatal endothelial repair and neovascularization. A large body of evidence from clinical, animal, and in vitro studies have shown that EPC numbers in circulation and their functionality reflect endogenous vascular regenerative capacity. Traditionally vitamin D is known to be beneficial for bone health and calcium metabolism and in the last two decades, its role in influencing CVD and cancer risk has generated significant interest. Observational studies have shown that low vitamin D levels are associated with an adverse cardiovascular risk profile. Still, Mendelian randomization studies and randomized control trials (RCTs) have not shown significant effects of vitamin D on cardiovascular events. The criticism regarding the RCTs on vitamin D and CVD is that they were not designed to investigate cardiovascular outcomes in vitamin D-deficient individuals. Overall, the association between vitamin D and CVD remains inconclusive. Recent clinical and experimental studies have demonstrated the beneficial role of vitamin D in increasing the circulatory level of EPC as well as their functionality. In this review we present evidence supporting the beneficial role of vitamin D in CVD through its modulation of EPC homeostasis.

Assessment of the Relationship Between CD34 Antigen and Vitamin D Level and Insulin Resistance in Patients With Type 2 Diabetes

Diabetes causes disorders in the performance of endothelial progenitor cells, and obesity and vitamin D deficiency are associated with endothelial dysfunction and cardiovascular disease. This case-control study investigated the relationship between serum CD34 antigen and vitamin D levels and insulin resistance in type 2 diabetes. The results showed that CD34 has a significant inverse relationship with BMI, A1C, fasting blood glucose, insulin resistance, and insulin levels and has a significant direct relationship with vitamin D levels. Both CD34 and vitamin D were found to be significantly associated with type 2 diabetes. The association between reduced CD34 and vitamin D levels with type 2 diabetes and increased insulin resistance suggests that these parameters may be helpful in assessing diabetes and predicting its complications.

Bradykinin Protects Human Endothelial Progenitor Cells from High-Glucose-Induced Senescence through B2 Receptor-Mediated Activation of the Akt/eNOS Signalling Pathway

BACKGROUND

Circulating endothelial progenitor cells (EPCs) play important roles in vascular repair. However, the mechanisms of high-glucose- (HG-) induced cord blood EPC senescence and the role of B2 receptor (B2R) remain unknown.

METHODS

Cord blood samples from 26 patients with gestational diabetes mellitus (GDM) and samples from 26 healthy controls were collected. B2R expression on circulating CD34+ cells of cord blood mononuclear cells (CBMCs) was detected using flow cytometry. The plasma concentrations of 8-isoprostaglandin F2α (8-iso-PGF2α) and nitric oxide (NO) were measured. EPCs were treated with HG (40 mM) alone or with bradykinin (BK) (1 nM). The B2R and eNOS small interfering RNAs (siRNAs) and the PI3K antagonist LY294002 were added to block B2R, eNOS, and PI3K separately. To determine the number of senescent cells, senescence-associated β-galactosidase (SA-β-gal) staining was performed. The level of mitochondrial reactive oxygen species (ROS) in EPCs was assessed by Mito-Sox staining. Cell viability was evaluated by Cell Counting Kit-8 (CCK-8) assays. Mitochondrial DNA (mtDNA) copy number and the relative length of telomeres were detected by real time-PCR. The distribution of human telomerase reverse transcriptase (hTERT) in the nucleus, cytosol, and mitochondria of EPCs was detected by immunofluorescence. The expression of B2R, p16, p21, p53, P-Ser473AKT, T-AKT, eNOS, and hTERT was demonstrated by Western blot.

RESULTS

B2R expression on circulating CD34+ cells of CBMCs was significantly reduced in patients with GDM compared to healthy controls. Furthermore, B2R expression on circulating CD34+ cells of CBMCs was inversely correlated with plasma 8-iso-PGF2α concentrations and positively correlated with plasma NO levels. BK treatment decreased EPC senescence and ROS generation. Furthermore, BK treatment of HG-exposed cells led to elevated P-Ser473AKT and eNOS protein expression compared with HG treatment alone. BK reduced hTERT translocation in HG-induced senescent EPCs. B2R siRNA, eNOS siRNA, and antagonist of the PI3K signalling pathway blocked the protective effects of BK.

CONCLUSION

BK, acting through PI3K-AKT-eNOS signalling pathways, reduced hTERT translocation, increased the relative length of telomeres while reducing mtDNA copy number, and finally protected against EPC senescence induced by HG.

Development of a multi-arm polyrotaxanes modified mesoporous silica-coated gold nanoplatform for protecting endothelial progenitor cells against high glucose environment

Recent study reported that endothelial progenitor cells (EPCs) have potential to treat diabetic macroangiopathy. High glucose environment of diabetes can affect the adhesion of EPCs by decreasing the expression of CXC chemokine receptor 4 (CXCR4) and affect the proliferation of EPCs by decreasing the expression of miR-126. The results showed that the cytotoxicity of GNR@MSNs@PEI to EPCs was significantly lower than PEI; the temperature of GNR@MSNs@PEI solution can be controlled between 38-40°C under 808 nm laser irradiation. 25.67 µg of pcDNA3.1-GFP-CXCR4 and 5.36 µg of FITC-miR-126 could be loaded in 1 mg of GNR@MSNs@PEI; GNR@MSNs@PEI has gene transfection almost the same as Lipofectamine 3000. Subsequent in vitro studies showed that pcDNA3.1-GFP-CXCR4 and miR-126 loaded GNR@MSNs@PEI can significantly increase the adhesion and proliferation and decrease the apoptosis of EPCs treated with high glucose under 808 nm laser irradiation. In conclusion, nano-carriers (GNR@MSNs@PEI) with high pcDNA3.1-CXCR4 and miR-126 loading capacity, high biocompatibility, well cell internalization, and controllable release ability were constructed to transfer CXCR4 expression plasmid (pcDNA3.1-CXCR4) and miR-126 into EPCs efficiently. Further in vitro studies indicated that pcDNA3.1-CXCR4 and miR-126-loaded GNR@MSNs@PEI could protect EPCs against high glucose-induced injury.

Type 1 diabetes patients increase CXCR4+ and CXCR7+ haematopoietic and endothelial progenitor cells with exercise, but the response is attenuated

Exercise mobilizes angiogenic cells, which stimulate vascular repair. However, limited research suggests exercise-induced increase of endothelial progenitor cell (EPCs) is completely lacking in type 1 diabetes (T1D). Clarification, along with investigating how T1D influences exercise-induced increases of other angiogenic cells (hematopoietic progenitor cells; HPCs) and cell surface expression of chemokine receptor 4 (CXCR4) and 7 (CXCR7), is needed. Thirty T1D patients and 30 matched non-diabetes controls completed 45 min of incline walking. Circulating HPCs (CD34⁺, CD34⁺CD45^dim) and EPCs (CD34⁺VEGFR2⁺, CD34⁺CD45^dimVEGFR2⁺), and subsequent expression of CXCR4 and CXCR7, were enumerated by flow cytometry at rest and post-exercise. Counts of HPCs, EPCs and expression of CXCR4 and CXCR7 were significantly lower at rest in the T1D group. In both groups, exercise increased circulating angiogenic cells. However, increases was largely attenuated in the T1D group, up to 55% lower, with CD34⁺ (331 ± 437 Δcells/mL vs. 734 ± 876 Δcells/mL p = 0.048), CD34⁺VEGFR2⁺ (171 ± 342 Δcells/mL vs. 303 ± 267 Δcells/mL, p = 0.006) and CD34⁺VEGFR2⁺CXCR4⁺ (126 ± 242 Δcells/mL vs. 218 ± 217 Δcells/mL, p = 0.040) significantly lower. Exercise-induced increases of angiogenic cells is possible in T1D patients, albeit attenuated compared to controls. Decreased mobilization likely results in reduced migration to, and repair of, vascular damage, potentially limiting the cardiovascular benefits of exercise.Trial registration: ISRCTN63739203.

Endothelial Progenitor Cells Dysfunctions and Cardiometabolic Disorders: From Mechanisms to Therapeutic Approaches

Metabolic syndrome (MetS) is a cluster of several disorders, such as hypertension, central obesity, dyslipidemia, hyperglycemia, insulin resistance and non-alcoholic fatty liver disease. Despite health policies based on the promotion of physical exercise, the reduction of calorie intake and the consumption of healthy food, there is still a global rise in the incidence and prevalence of MetS in the world. This phenomenon can partly be explained by the fact that adverse events in the perinatal period can increase the susceptibility to develop cardiometabolic diseases in adulthood. Individuals born after intrauterine growth restriction (IUGR) are particularly at risk of developing cardiovascular diseases (CVD) and metabolic disorders later in life. It has been shown that alterations in the structural and functional integrity of the endothelium can lead to the development of cardiometabolic diseases. The endothelial progenitor cells (EPCs) are circulating components of the endothelium playing a major role in vascular homeostasis. An association has been found between the maintenance of endothelial structure and function by EPCs and their ability to differentiate and repair damaged endothelial tissue. In this narrative review, we explore the alterations of EPCs observed in individuals with cardiometabolic disorders, describe some mechanisms related to such dysfunction and propose some therapeutical approaches to reverse the EPCs dysfunction.

Growth Factor Deregulation and Emerging Role of Phosphatases in Diabetic Peripheral Artery Disease

Peripheral artery disease is caused by atherosclerosis of lower extremity arteries leading to the loss of blood perfusion and subsequent critical ischemia. The presence of diabetes mellitus is an important risk factor that greatly increases the incidence, the progression and the severity of the disease. In addition to accelerated disease progression, diabetic patients are also more susceptible to develop serious impairment of their walking abilities through an increased risk of lower limb amputation. Hyperglycemia is known to alter the physiological development of collateral arteries in response to ischemia. Deregulation in the production of several critical pro-angiogenic factors has been reported in diabetes along with vascular cell unresponsiveness in initiating angiogenic processes. Among the multiple molecular mechanisms involved in the angiogenic response, protein tyrosine phosphatases are potent regulators by dephosphorylating pro-angiogenic tyrosine kinase receptors. However, evidence has indicated that diabetes-induced deregulation of phosphatases contributes to the progression of several micro and macrovascular complications. This review provides an overview of growth factor alterations in the context of diabetes and peripheral artery disease, as well as a description of the role of phosphatases in the regulation of angiogenic pathways followed by an analysis of the effects of hyperglycemia on the modulation of protein tyrosine phosphatase expression and activity. Knowledge of the role of phosphatases in diabetic peripheral artery disease will help the development of future therapeutics to locally regulate phosphatases and improve angiogenesis.

Abnormal DNA Methylation Induced by Hyperglycemia Reduces CXCR 4 Gene Expression in CD 34+ Stem Cells

Background CD 34⁺ stem/progenitor cells are involved in vascular homeostasis and in neovascularization of ischemic tissues. The number of circulating CD 34⁺ stem cells is a predictive biomarker of adverse cardiovascular outcomes in diabetic patients. Here, we provide evidence that hyperglycemia can be "memorized" by the stem cells through epigenetic changes that contribute to onset and maintenance of their dysfunction in diabetes mellitus. Methods and Results Cord-blood-derived CD 34⁺ stem cells exposed to high glucose displayed increased reactive oxygen species production, overexpression of p66^shc gene, and downregulation of antioxidant genes catalase and manganese superoxide dismutase when compared with normoglycemic cells. This altered oxidative state was associated with impaired migration ability toward stromal-cell-derived factor 1 alpha and reduced protein and mRNA expression of the C-X-C chemokine receptor type 4 ( CXCR 4) receptor. The methylation analysis by bisulfite Sanger sequencing of the CXCR 4 promoter revealed a significant increase in DNA methylation density in high-glucose CD 34⁺ stem cells that negatively correlated with mRNA expression (Pearson r=-0.76; P=0.004). Consistently, we found, by chromatin immunoprecipitation assay, a more transcriptionally inactive chromatin conformation and reduced RNA polymerase II engagement on the CXCR 4 promoter. Notably, alteration of CXCR 4 DNA methylation, as well as transcriptional and functional defects, persisted in high-glucose CD 34⁺ stem cells despite recovery in normoglycemic conditions. Importantly, such an epigenetic modification was thoroughly confirmed in bone marrow CD 34⁺ stem cells isolated from sternal biopsies of diabetic patients undergoing coronary bypass surgery. Conclusions CD 34⁺ stem cells "memorize" the hyperglycemic environment in the form of epigenetic modifications that collude to alter CXCR 4 receptor expression and migration.

Effects of Complement Regulators and Chemokine Receptors in Type 2 Diabetes

CD55 and CD59 are complement regulatory proteins suggested to be related with progression of diabetes and its complications. The stromal cell-derived factor 1 (SDF-1) and C-X-C chemokine receptor type 4 (CXCR-4) are chemokine proteins. We aimed to investigate the relation of CD55 and CD59 expression levels and polymorphisms of SDF-1 and CXCR-4 with type 2 diabetes mellitus (T2DM) and its complications. Seventy-five T2DM patients and 73 controls were enrolled. Expression levels of CD55 and CD59 were measured by FACS Calibur; qRT-PCR was used to determine SDF-1 and CXCR-4 gene polymorphisms. CD55 and CD59 expressions in patients with nephropathy, retinopathy and cardiovascular disease were significantly lower than controls. Frequency of CXCR-4 T allele carrying was high in patients and created 1.6 fold risk for the disease (p = .07). CXCR-4 a allele carriers had decreased nephropathy; although there was no statistical significance in carrying CXCR-4 T allele, presence of nephropathy was approximately 2 times higher (p = .254). The nephropathy risk increased 10-fold in CXCR-4 TT genotype carriers (p = .02). All SDF-1 CC genotype carriers had retinopathy, so, it was considered that the CC genotype was effective in retinopathy development (p = .031). For the presence of cardiovascular disease, significant difference was observed for SDF-1 genotypes. Increased cardiovascular risk of 5- and 1.9-fold in SDF-1 T (p = .007) and CXCR-4 T (p = .216) allele carriers, respectively, was observed. We suggest that CD55 and CD59 protein levels and SDF-1 and CXCR-4 have predictive importance in process, complications and tendency of T2DM.

When Good Guys Turn Bad: Bone Marrow's and Hematopoietic Stem Cells' Role in the Pathobiology of Diabetic Complications

Diabetes strongly contributes to the development of cardiovascular disease, the leading cause of mortality and morbidity in these patients. It is widely accepted that hyperglycemia impairs hematopoietic stem/progenitor cell (HSPC) mobilization from the bone marrow (BM) by inducing stem cell niche dysfunction. Moreover, a recent study demonstrated that type 2 diabetic patients are characterized by significant depletion of circulating provascular progenitor cells and increased frequency of inflammatory cells. This unbalance, potentially responsible for the reduction of intrinsic vascular homeostatic capacity and for the establishment of a low-grade inflammatory status, suggests that bone BM-derived HSPCs are not only victims but also active perpetrators in diabetic complications. In this review, we will discuss the most recent literature on the molecular mechanisms underpinning hyperglycemia-mediated BM dysfunction and differentiation abnormality of HSPCs. Moreover, a section will be dedicated to the new glucose-lowering therapies that by specifically targeting the culprits may prevent or treat diabetic complications.

Identification of differentially expressed genes in the endothelial precursor cells of patients with type 2 diabetes mellitus by bioinformatics analysis

Type 2 diabetes mellitus (DM) is a metabolic disease with worldwide prevalence that is associated with a decrease in the number and function of endothelial progenitor cells (EPCs). The aim of the present study was to explore the potential hub genes of EPCs in patients with type 2 DM. Differentially expressed genes (DEGs) were screened from a public microarray dataset (accession no. GSE43950). Pathway and functional enrichment analyses were performed using the Database for Annotation, Visualization and Integrated Discovery. The protein-protein interaction (PPI) network was visualized. The most significantly clustered modules and hub genes were identified using Cytoscape. Furthermore, hub genes were validated by quantitative PCR analysis of EPCs isolated from diabetic and normal subjects. Subsequently, weighted gene co-expression network analysis (WGCNA) was performed to identify the modules incorporating the genes exhibiting the most significant variance. A total of 970 DEGs were obtained and they were mainly accumulated in inflammation-associated pathways. A total of 9 hub genes were extracted from the PPI network and the highest differential expression was determined for the interleukin 8 (IL8) and CXC chemokine ligand 1 (CXCL1) genes. In the WGCNA performed to determine the modules associated with type 2 DM, one module incorporated IL8 and CXCL1. Finally, pathway enrichment of 10% genes in the pink module ordered by intramodular connectivity (IC) was associated with the IL17 and the chemokine signaling pathways. The present results revealed that the expression of IL8 and CXCL1 may serve important roles in the pathophysiology of EPCs during type 2 DM and inflammatory response may be critical for the reduced number and hypofunction of EPCs isolated from patients with diabetes.

Molecular interplay between microRNA-130a and PTEN in palmitic acid-mediated impaired function of endothelial progenitor cells: Effects of metformin

Metformin serves an important role in improving the functions of endothelial progenitor cells (EPCs). MicroRNAs (miRNAs), small non‑coding RNAs, have been investigated as significant regulators of EPC vascular functions. The present study investigated the molecular crosstalk between metformin and miRNA‑130a (miR‑130a) in the functions of EPCs exposed to palmitic acid (PA). Isolated EPCs were treated with metformin, PA, and metformin + PA, respectively. Cell Counting Kit‑8, Transwell and Matrigel assays were performed to detect the proliferation, migration and tube formation ability of EPCs following different treatments. The expression of miR‑130a, phosphatase and tensin homolog (PTEN) and phosphorylated‑AKT was analyzed by reverse transcription‑quantitative polymerase chain reaction and western blotting. The specific mechanism underlying the function of metformin in EPCs was further elucidated by transfecting miR‑130a mimics and inhibitor to overexpress and inhibit the expression of miR‑130a in EPCs, respectively. EPCs exhibited impaired functions of proliferation (P<0.01 compared with the control), migration (P<0.01 compared with the control) and tube formation (P<0.01 compared with the control) following treatment with PA, and the expression levels of miR‑130a and PTEN were decreased and increased, respectively. However, the presence of metformin, or the overexpression of miR‑130a using miR‑130a mimic alleviated the impairment of angiogenesis and proliferation, decreased the expression of PTEN and activated the phosphoinositide‑3 kinase/AKT pathway in EPCs exposed to PA. By contrast, downregulating the expression of miR‑130a with a miR‑130a inhibitor reversed the metformin‑mediated protection. These results demonstrate the beneficial effect of miR‑130a/PTEN on EPC functions, which can be regulated by metformin. The effects of metformin on improving PA‑induced EPC dysfunction are mediated by miR‑130a and PTEN, which may assist in the prevention and/or treatment of diabetic vascular disease.

Update on the impact of type 2 diabetes mellitus on bone metabolism and material properties

The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide, especially as a result of our aging society, high caloric intake and sedentary lifestyle. Besides the well-known complications of T2DM on the cardiovascular system, the eyes, kidneys and nerves, bone strength is also impaired in diabetic patients. Patients with T2DM have a 40-70% increased risk for fractures, despite having a normal to increased bone mineral density, suggesting that other factors besides bone quantity must account for increased bone fragility. This review summarizes the current knowledge on the complex effects of T2DM on bone including effects on bone cells, bone material properties and other endocrine systems that subsequently affect bone, discusses the effects of T2DM medications on bone and concludes with a model identifying factors that may contribute to poor bone quality and increased bone fragility in T2DM.

ADSC-conditioned media elicit an ex vivo anti-inflammatory macrophage response

Obesity-associated inflammatory mechanisms play a key role in the pathogenesis of metabolic-related diseases. Failure of anti-inflammatory control mechanisms within adipose tissue and peripheral blood mononuclear cells (PBMCs) have been implicated in disease progression. This study investigated the efficacy of allogeneic adipose tissue-derived mesenchymal stem cells conditioned media (ADSC-CM) to counteract persistent inflammation by inducing an anti-inflammatory phenotype and cytokine response within PBMCs derived from patients with and without metabolic syndrome. Forty six (n=46) mixed ancestry females (18 - 45 years) were subdivided into a) healthy lean (HL) (n=10) (BMI < 25 kg/m2), b) overweight/obese (OW/OB) (BMI ≥ 25 kg/m2, < 3 metabolic risk factors) (n=22) and c) metabolic syndrome (MetS) (visceral adiposity , ≥ 3 metabolic risk factors) (n=14) groups. Body composition (DXA scan), metabolic (cholesterol, HDL, LDL, triglycerides, blood glucose) and inflammatory profiles (38-Plex cytokine panel) were determined. PBMCs were isolated from whole blood and treated ex vivo with either i) autologous participant-derived serum ii) ADSCs-CM or iii) a successive treatment regime. The activation status (CD11b+) and intracellular cytokine (IL6, IL10, TNFa) expression were determined in M1 (CD68+CD206-CD163-) and M2 (CD68+CD163+ CD206+) macrophage populations using flow cytometry. ADSC-CM treatment, promoted a M2 macrophage phenotype and induced IL10 expression, this was most pronounced in the OW/OB group. This response is likely mediated by multiple complementing factors within ADSC-CM, yet to be identified. This study is the first to demonstrate the therapeutic potential of ADSC-CM to restore the inflammatory balance in immune compromised obese individuals.

Microvascular Density and Circulating Endothelial Progenitor Cells Before and After Treatment with Incretin Mimetics in Diabetic Patients

INTRODUCTION

Glucagon-like peptide 1-receptor agonists (incretin mimetics) and dipeptidyl peptidase-4 inhibitors (incretin enhancers) have been recently introduced in the treatment of diabetes mellitus. In particular, incretin mimetics seems to have ancillary antioxidant/antinflammatory properties that might be involved in endothelial protection.

AIM

To investigate the effect of incretin mimetic therapy (liraglutide, exenatide) given to 11 patients with type 2 diabetes mellitus, on circulating endothelial progenitor cells (EPCs) (bone marrow-derived cells possibly participating in neovascularization and endothelial protection and repair) and capillary density.

METHODS

Four diabetic patients were treated with exenatide (5 μg twice daily for 4 weeks and then 10 μg twice daily for 3 weeks) and 7 with liraglutide (0.6 mg per day for 1 week and then 1.2 mg per day for 3 weeks). Peripheral venous blood samples were obtained before treatment (basal) and after 4 week in patients treated with liraglutide, and after 4 and 7 weeks in patients treated with exenatide, since drug titration is usually longer. EPCs were evaluated by flow cytometry as CD34⁺/KDR⁺ cells. Capillary density was evaluated by videomicroscopy, before and after venous congestion, in the dorsum of the 4th finger.

RESULTS

Patients treated with liraglutide (6 males 1 female, age 54 ± 12 years) showed a decrease in body mass index and blood pressure during treatment, while patients treated with exenatide (3 males 1 female, age 57 ± 6 years) did not show any relevant change. EPCs were significantly increased after treatment with exenatide, but not after treatment with liraglutide. Capillary density was slightly increased only after 4 weeks of treatment with exenatide, however the increase was no longer present at the final evaluation.

CONCLUSIONS

Treatment with exenatide, but not with liraglutide, was able to increase the number of circulating EPCs, possibly through an antioxidative/antiinflammatory effect.

Migratory, metabolic and functional alterations of fibrocytes in type 2 diabetes

Fibrocytes are bloodborne mesenchymal progenitor cells that are recruited to injured tissue sites and contribute to the repair process by acquiring a myofibroblast-like phenotype and producing extracellular matrix components and growth factors. Treatment with normal fibrocytes or their exosomes restores the ability of genetically diabetic mice to heal skin wounds, suggesting the existence of dysfunctional alterations in diabetic fibrocytes. This study compared the migratory, metabolic and functional characteristics of fibrocytes from patients with type 2 diabetes (T2DPs) and healthy controls (HCs). It was found that the frequency of these cells was abnormally low in the peripheral blood of T2DPs. Diabetic fibrocytes showed reduced expression of the C-X-C motif and C-C motif chemokine receptors (CXCR)4, (CCR)5, and CCR7, and demonstrated reduced migration in response to their ligands (CXCL)12, (CCL)5, and CCL21. They exhibited increased expression of the receptor for advanced glycation end product, suppression of the alternative AGE receptor 1, increased intracellular concentrations of AGEs, decreased expression of sirtuin-1 and elevated oxidative stress. In short-term cultures, fibrocytes from T2DPs released larger amounts of proinflammatory cytokines than those from HCs. Unlike normal fibrocytes, diabetic fibrocytes did not exhibit increased expression of type I collagen and α-smooth muscle actin on stimulation with transforming growth factor (TGF)-β1 and this abnormal response was associated with downregulation of TGF-β1 type II receptor on the cell surface. Study findings uncover multiple migratory and functional alterations of diabetic fibrocytes that may contribute to explain why T2DPs experience impaired wound healing and chronic ulcers. © 2018 IUBMB Life, 70(11):1122-1132, 2018.

Long-term Prediction of Cardiovascular Outcomes by Circulating CD34+ and CD34+CD133+ Stem Cells in Patients With Type 2 Diabetes

OBJECTIVE

Cardiovascular risk varies substantially in the population with diabetes, and biomarkers can improve risk stratification. Circulating stem cells predict future cardiovascular events and death, but data for the population with diabetes are scant. In this study we evaluated the ability of circulating stem cell levels to predict future cardiovascular outcomes and improve risk discrimination in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A cohort of 187 patients with type 2 diabetes was monitored for a median of 6.1 years. The primary outcome was time to a first cardiovascular event, defined as 3-point major adverse cardiovascular event (cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke) plus hospitalization for cardiovascular causes. At baseline, we measured six stem/progenitor cell phenotypes in peripheral blood based on expression of CD34, CD133, and KDR.

RESULTS

The primary outcome occurred in 48 patients (4.5/100 patient-years). Patients with incident cardiovascular events had significantly lower CD34⁺ and CD34⁺CD133⁺ cells than those without. Higher rates of cardiovascular events occurred in patients with below median levels of CD34⁺ and CD34⁺CD133⁺. In Cox proportional hazards regression analyses, a reduced CD34⁺ (hazard ratio 2.21 [95% CI 1.14-4.29]) and CD34⁺CD133⁺ (2.98 [1.46-6.08]) cell count independently predicted future events. Addition of the CD34⁺ cell count to the reference model or the UK Prospective Diabetes Study risk engine improved C statistics, continuous net reclassification improvement, and/or integrated discrimination index.

CONCLUSIONS

In patients with type 2 diabetes, a reduced baseline level of circulating CD34⁺ stem cells predicts adverse cardiovascular outcomes up to 6 years later and improves risk stratification.

Modulating putative endothelial progenitor cells for the treatment of endothelial dysfunction and cardiovascular complications in diabetes

Diabetes induces a decrease in the number and function of different pro-angiogenic cell types generically designated as putative endothelial progenitor cells (EPC), which encompasses cells from myeloid origin that act in a paracrine fashion to promote angiogenesis and putative "true" EPC that contribute to endothelial replacement. This not only compromises neovasculogenesis in ischemic tissues but also impairs, at an early stage, the reendotheliziation process at sites of injury, contributing to the development of endothelial dysfunction and cardiovascular complications. Hyperglycemia, insulin resistance and dyslipidemia promote putative EPC dysregulation by affecting the SDF-1/CXCR-4 and NO pathways and the p53/SIRT1/p66Shc axis that contribute to their mobilization, migration, homing and vasculogenic properties. To optimize the clinical management of patients with hypoglycemic agents, statins and renin-angiotensin system inhibitors, which display pleiotropic effects on putative EPC, is a first step to improve their number and angiogenic potential but specific strategies are needed. Among them, mobilizing therapies based on G-CSF, erythropoietin or CXCR-4 antagonism have been developed to increase putative EPC number to treat ischemic diseases with or without prior cell isolation and transplantation. Growth factors, genetic and pharmacological strategies are also evaluated to improve ex vivo cultured EPC function before transplantation. Moreover, pharmacological agents increasing in vivo the bioavailability of NO and other endothelial factors demonstrated beneficial effects on neovascularization in diabetic ischemic models but their effects on endothelial dysfunction remain poorly evaluated. More experiments are warranted to develop orally available drugs and specific agents targeting p66Shc to reverse putative EPC dysfunction in the expected goal of preventing endothelial dysfunction and diabetic cardiovascular complications.

Angiogenesis and Inflammation Crosstalk in Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most prevalent microvascular complications of diabetes and one of the most frequent causes of blindness in active age. Etiopathogenesis behind this important complication is related to several biochemical, hemodynamic and endocrine mechanisms with a preponderant initial role assumed by polyol pathways, increment of growth factors, accumulation of advanced glycation end products (AGE), activation of protein kinase C (PKC), activation of the renin-angiotensin-aldosterone system (RAAS), and leukostasis. Chronic and sustained hyperglycemia works as a trigger to the early alterations that culminate in vascular dysfunction. Hypoxia also plays an essential role in disease progression with promotion of neovascularization and vascular dystrophies with vitreous hemorrhages induction. Thus, the accumulation of fluids and protein exudates in ocular cavities leads to an opacity augmentation of the cornea that associated to neurodegeneration results in vision loss, being this a devastating characteristic of the disease final stage. During disease progression, inflammatory molecules are produced and angiogenesis occur. Furthermore, VEGF is overexpressed by the maintained hyperglycemic environment and up-regulated by tissue hypoxia. Also pro-inflammatory mediators regulated by cytokines, such as tumor necrosis factor (TNF-α) and interleukin-1 beta (IL-1β), and growth factors leads to the progression of these processes, culminating in vasopermeability (diabetes macular edema) and/or pathological angiogenesis (proliferative diabetic retinopathy). It was found a mutual contribution between inflammation and angiogenesis along the process. J. Cell. Biochem. 117: 2443-2453, 2016. © 2016 Wiley Periodicals, Inc.

Concise Review: Perspectives and Clinical Implications of Bone Marrow and Circulating Stem Cell Defects in Diabetes

Diabetes mellitus is a complex systemic disease characterized by severe morbidity and excess mortality. The burden of its multiorgan complications relies on an imbalance between hyperglycemic cell damage and defective endogenous reparative mechanisms. Inflammation and abnormalities in several hematopoietic components are typically found in diabetes. The discovery that diabetes reduces circulating stem/progenitor cells and impairs their function has opened an entire new field of study where diabetology comes into contact with hematology and regenerative medicine. It is being progressively recognized that such rare circulating cell populations mirror finely regulated processes involved in hematopoiesis, immunosurveillance, and peripheral tissue homeostasis. From a clinical perspective, pauperization of circulating stem cells predicts adverse outcomes and death. Furthermore, studies in murine models and humans have identified the bone marrow (BM) as a previously neglected site of diabetic end-organ damage, characterized by microangiopathy, neuropathy, fat deposition, and inflammation. As a result, diabetes impairs the mobilization of BM stem/progenitor cells, a defect known as mobilopathy or myelokathexis, with negative consequences for physiologic hematopoiesis, immune regulation, and tissue regeneration. A better understanding of the molecular and cellular processes that govern the BM stem cell niche, cell mobilization, and kinetics in peripheral tissues may uncover new therapeutic strategies for patients with diabetes. This concise review summarizes the current knowledge on the interplay between the BM, circulating stem cells, and diabetes, and sets the stages for future developments in the field. Stem Cells 2017;35:106-116.

Collection and immunoselection of CD34+ cells: the impact of age, sex, and diabetes in patients with chronic heart failure

BACKGROUND

Mobilized peripheral blood is the most common source of CD34+ cells intended for transplantations. The collection and enrichment of CD34+ cells could be affected by various factors and there are some controversies regarding the effects of patient-related factors. The aim of this study was to assess the impact of age, sex, and diabetes on the CD34+ cell grafts in patients with chronic heart failure.

STUDY DESIGN AND METHODS

Cell grafts from 100 adult patients scheduled for autologous CD34+ cell transplantation were investigated. The CD34+ cells were collected using leukapheresis after granulocyte-colony-stimulating factor mobilization and further enriched using the immunomagnetic CD34+ selection. The number of CD34+ cells and their viability were determined by flow cytometry.

RESULTS

Older patients had significantly lower CD34+ cell counts than younger patients. The differences between men and women were not found. There was a trend toward an inverse relationship between diabetes and the CD34+ cell count, however, without any significance. No differences in the CD34+ cell viability (97.6% before and 97.9% after selection) were found. The mean CD34+ cell recovery was 59.7% and was not statistically different between age groups, sex, and diabetic patients.

CONCLUSION

Before the CD34+ cells are collected the patient's age should be considered. The study did not demonstrate a significant impact of sex and diabetes on the CD34+ cell count. While age and sex did not affect the immunoselection process, diabetes slightly reduced cell recovery. Cell viabilities before and after the cell enrichment were comparable between the tested samples.

Endothelial Progenitor Cells for Diagnosis and Prognosis in Cardiovascular Disease

Objective. To identify, evaluate, and synthesize evidence on the predictive power of circulating endothelial progenitor cells (EPCs) in cardiovascular disease, through a systematic review of quantitative studies. Data Sources. MEDLINE was searched using keywords related to "endothelial progenitor cells" and "endothelium" and, for the different categories, respectively, "smoking"; "blood pressure"; "diabetes mellitus" or "insulin resistance"; "dyslipidemia"; "aging" or "elderly"; "angina pectoris" or "myocardial infarction"; "stroke" or "cerebrovascular disease"; "homocysteine"; "C-reactive protein"; "vitamin D". Study Selection. Database hits were evaluated against explicit inclusion criteria. From 927 database hits, 43 quantitative studies were included. Data Syntheses. EPC count has been suggested for cardiovascular risk estimation in the clinical practice, since it is currently accepted that EPCs can work as proangiogenic support cells, maintaining their importance as regenerative/reparative potential, and also as prognostic markers. Conclusions. EPCs showed an important role in identifying cardiovascular risk conditions, and to suggest their evaluation as predictor of outcomes appears to be reasonable in different defined clinical settings. Due to their capability of proliferation, circulation, and the development of functional progeny, great interest has been directed to therapeutic use of progenitor cells in atherosclerotic diseases. This trial is registered with registration number: Prospero CRD42015023717.

Sitagliptin, a dipeptidyl peptidase-4 inhibitor, increases the number of circulating CD34⁺CXCR4⁺ cells in patients with type 2 diabetes

We investigated the effects of sitagliptin, a dipeptidyl peptidase (DPP)-4 inhibitor, on the number of circulating CD34(+)CXCR4(+)cells, a candidate for endothelial progenitor cells (EPCs), plasma levels of stromal cell-derived factor (SDF)-1α, a ligand for CXCR4 receptor and a substrate for DPP-4, and plasma levels of interferon-inducible protein (IP)-10, for a substrate for DPP-4, in patients with type 2 diabetes. We studied 30 consecutive patients with type 2 diabetes who had poor glycemic control despite treatment with metformin and/or sulfonylurea. Thirty diabetic patients were randomized in a 2:1 ratio into a sitagliptin (50 mg/day) treatment group or an active placebo group (glimepiride 1 mg/day) for 12 weeks. Both groups showed similar improvements in glycemic control. The number of circulating CD34(+)CXCR4(+) cells was increased from 30.5 (20.0, 47.0)/10(6) cells at baseline to 55.5 (31.5, 80.5)/10(6) cells at 12 weeks of treatment with 50 mg/day sitagliptin (P = 0.0014), while showing no significant changes in patients treated with glimepiride. Plasma levels of SDF-1α and IP-10, both physiological substrates of endogenous DPP-4 and chemokines, were significantly decreased at 12 weeks of sitagliptin treatment. In conclusion, treatment with sitagliptin increased the number of circulating CD34(+)CXCR4(+) cells by approximately 2-fold in patients with type 2 diabetes.

Heme-Mediated Induction of CXCL10 and Depletion of CD34+ Progenitor Cells Is Toll-Like Receptor 4 Dependent

Plasmodium falciparum infection can cause microvascular dysfunction, cerebral encephalopathy and death if untreated. We have previously shown that high concentrations of free heme, and C-X-C motif chemokine 10 (CXCL10) in sera of malaria patients induce apoptosis in microvascular endothelial and neuronal cells contributing to vascular dysfunction, blood-brain barrier (BBB) damage and mortality. Endothelial progenitor cells (EPC) are microvascular endothelial cell precursors partly responsible for repair and regeneration of damaged BBB endothelium. Studies have shown that EPC's are depleted in severe malaria patients, but the mechanisms mediating this phenomenon are unknown. Toll-like receptors recognize a wide variety of pathogen-associated molecular patterns generated by pathogens such as bacteria and parasites. We tested the hypothesis that EPC depletion during malaria pathogenesis is a function of heme-induced apoptosis mediated by CXCL10 induction and toll-like receptor (TLR) activation. Heme and CXCL10 concentrations in plasma obtained from malaria patients were elevated compared with non-malaria subjects. EPC numbers were significantly decreased in malaria patients (P < 0.02) and TLR4 expression was significantly elevated in vivo. These findings were confirmed in EPC precursors in vitro; where it was determined that heme-induced apoptosis and CXCL10 expression was TLR4-mediated. We conclude that increased serum heme mediates depletion of EPC during malaria pathogenesis.

Vascular repair strategies in type 2 diabetes: novel insights

Impaired functions of vascular cells are responsible for the majority of complications in patients with type 2 diabetes (T2D). Recently a better understanding of mechanisms contributing to development of vascular dysfunction and the role of systemic inflammatory activation and functional alterations of several secretory organs, of which adipose tissue has more recently been investigated, has been achieved. Notably, the progression of vascular disease within the context of T2D appears to be driven by a multitude of incremental signaling shifts. Hence, successful therapies need to target several mechanisms in parallel, and over a long time period. This review will summarize the latest molecular strategies and translational developments of cardiovascular therapy in patients with T2D.

Stem cell therapies in the treatment of diabetic retinopathy and keratopathy

Nonproliferative diabetic retinopathy (DR) is characterized by multiple degenerative changes that could be potentially corrected by stem cell therapies. Most studies so far have attempted to alleviate typical abnormalities of early retinopathy, including vascular hyperpermeability, capillary closure and pericyte dropout. Success was reported with adult stem cells (vascular progenitors or adipose stem cells), as well as induced pluripotent stem cells from cord blood. The cells were able to associate with damaged vessels in both pericyte and endothelial lining positions in models of DR and ischemia-reperfusion. In some diabetic models, functional amelioration of vasculature and electroretinograms was noted. Another approach for endogenous progenitor cell therapy is to normalize dysfunctional diabetic bone marrow and residing endothelial progenitors using NO donors, PPAR-δ and -γ agonists, or inhibition of TGF-β. A potentially important strategy would be to reduce neuropathy by stem cell inoculations, either naïve (e.g., paracrine-acting adipose stem cells) or secreting specific neuroprotectants, such as ciliary neurotrophic factor or brain-derived neurotrophic factor that showed benefit in amyotrophic lateral sclerosis and Parkinson's disease. Recent advances in stem cell therapies for diabetic retinal microangiopathy may form the basis of first clinical trials in the near future. Additionally, stem cell therapies may prove beneficial for diabetic corneal disease (diabetic keratopathy) with pronounced epithelial stem cell dysfunction.

Epigenetic Changes in Endothelial Progenitors as a Possible Cellular Basis for Glycemic Memory in Diabetic Vascular Complications

The vascular complications of diabetes significantly impact the quality of life and mortality in diabetic patients. Extensive evidence from various human clinical trials has clearly established that a period of poor glycemic control early in the disease process carries negative consequences, such as an increase in the development and progression of vascular complications that becomes evident many years later. Importantly, intensive glycemic control established later in the disease process cannot reverse or slow down the onset or progression of diabetic vasculopathy. This has been named the glycemic memory phenomenon. Scientists have successfully modelled glycemic memory using various in vitro and in vivo systems. This review emphasizes that oxidative stress and accumulation of advanced glycation end products are key factors driving glycemic memory in endothelial cells. Furthermore, various epigenetic marks have been proposed to closely associate with vascular glycemic memory. In addition, we comment on the importance of endothelial progenitors and their role as endogenous vasoreparative cells that are negatively impacted by the diabetic milieu and may constitute a "carrier" of glycemic memory. Considering the potential of endothelial progenitor-based cytotherapies, future studies on their glycemic memory are warranted to develop epigenetics-based therapeutics targeting diabetic vascular complications.

Diabetes, Endothelial Dysfunction, and Vascular Repair: What Should a Diabetologist Keep His Eye on?

Cardiovascular complications are the most common complications of diabetes mellitus. A prominent attribute of diabetic cardiovascular complications is accelerated atherosclerosis, considered as a still incurable disease, at least at more advanced stages. The discovery of endothelial progenitor cells (EPCs), able to replace old and injured mature endothelial cells and capable of differentiating into healthy and functional endothelial cells, has offered the prospect of merging the traditional theories on the pathogenesis of atherosclerosis with evolving concepts of vascular biology. The literature supports the notion that EPC alterations are involved in the pathogenesis of vascular diseases in diabetics, but at present many questions remain unanswered. In this review the aspects linking endothelial progenitor cells to the altered vascular biology in diabetes mellitus are discussed.

The endothelium in diabetic nephropathy

Diabetes is characterised by widespread endothelial cell dysfunction that underlies the development of both the micro- and macrovascular complications of the disease, including nephropathy, cardiomyopathy, and non-proliferative retinopathy. In the kidney, major changes are noted in glomerular endothelial cell structure in their fenestrations and glycocalyx. These changes, along with endothelial cell loss and capillary rarefaction in both the glomerulus and tubulointerstitium, lead to the progressive loss of glomerular filtration that render diabetes the most common cause of end-stage renal disease in much of the developed world. New treatments in diabetes that directly address the abnormal structure and function of the endothelial cell are desperately needed.

Impact of prior chronic statin therapy and high-intensity statin therapy at discharge on circulating endothelial progenitor cell levels in patients with acute myocardial infarction: a prospective observational study

BACKGROUND

Endothelial progenitor stem cells (EPCs) are mobilized to the peripheral circulation in response to myocardial ischemia, playing a crucial role in vascular repair. Statins have been shown to stimulate EPCs. However, neither the impact of previous statin therapy on EPC response of acute myocardial infarction (AMI) patients nor the effect of post-AMI high-intensity statin therapy on the evolution of circulating EPC levels has yet been addressed. Therefore, we aimed to compare circulating EPC levels between patients receiving long-term statin therapy before the AMI and statin-naive patients and to assess the impact of high-intensity statin therapy at discharge on the evolution of circulating EPCs post-AMI.

METHODS

This is a prospective observational study of 100 AMI patients. Circulating EPCs (CD45dimCD34 + KDR + cells) and their subpopulation coexpressing the homing marker CXCR4 were quantified by the high-performance flow cytometer FACSCanto II in whole blood, in two different moments: within the first 24 h of admission and 3 months post-AMI. Patients were followed up clinically for 2 years.

RESULTS

Patients previously treated with statins had significantly higher levels of EPCs coexpressing CXCR4 (1.9 ± 1.4 vs. 1.3 ± 1.0 cells/1,000,000 events, p = 0.031) than statin-naive patients. In addition, the subanalysis of diabetics (N = 38) also revealed that patients previously on statins had significantly greater numbers of both CD45dimCD34 + KDR + CXCR4+ cells (p = 0.024) and CD45dimCD34 + KDR + CD133+ cells (p = 0.022) than statin-naive patients. Regarding the evolution of EPC levels after the AMI, patients not on a high-intensity statin therapy at discharge had a significant reduction of CD45dimCD34 + KDR + and CD45dimCD34 + KDR + CXCR4+ cells from baseline to 3 months follow-up (p = 0.031 and p = 0.005, respectively). However, patients discharged on a high-intensity statin therapy maintained circulating levels of all EPC populations, presenting at 3 months of follow-up significantly higher EPC levels than patients not on an intensive statin therapy. Moreover, the high-intensity statin treatment group had significantly better clinical outcomes during the 2-year follow-up period than patients not discharged on a high-intensity statin therapy.

CONCLUSION

Chronic statin therapy prior to an AMI strongly enhances the response of EPCs to myocardial ischemia, even in diabetic patients. Furthermore, high-intensity statin therapy after an AMI prevents the expected decrease of circulating EPC levels during follow-up. These results reinforce the importance of an early and intensive statin therapy in AMI patients.

Glucose metabolism, hyperosmotic stress, and reprogramming of somatic cells

The availability of glucose and oxygen are important regulatory elements that help directing stem cell fate. In the undifferentiated state, stem cells, and their artificially reprogrammed equivalent-induced pluripotent stem cells (iPS) are characterized by limited oxidative capacity and active anaerobic glycolysis. Recent studies have shown that pluripotency-a characteristic of staminality-is associated with a poorly developed mitochondrial patrimony, while differentiation is accompanied by an activation of mitochondrial biogenesis. Besides being an important energy source in hypoxia, high glucose level results in hyperosmotic stress. The identification of specific metabolic pathways and biophysical factors that regulate stem cell fate, including high glucose in the extracellular medium, may therefore facilitate reprogramming efficiency and control the differentiation and fate of iPS cells, which are increasingly being explored as therapeutic tools. In this article, we review recent knowledge of the role of glucose metabolism and high glucose level as major anaerobic energy source, and a determinant of osmolarity as possible tools for reprogramming therapies in clinical applications. As in the diabetic setting hyperglycemia negatively affect the stem/progenitor cell fate and likely somatic reprogramming, we also discuss the in vivo potential transferability of the available in vitro findings.

Specific role of impaired glucose metabolism and diabetes mellitus in endothelial progenitor cell characteristics and function

The disease burden of diabetes mellitus (DM) and its associated cardiovascular complications represent a growing and major global health problem. Recent studies suggest that circulating exogenous endothelial progenitor cells (EPCs) play an important role in endothelial repair and neovascularization at sites of injury or ischemia. Both experimental and clinical studies have demonstrated that hyperglycemia related to DM can induce alterations to EPCs. The reduction and dysfunction of EPCs related to DM correlate with the occurrence and severity of microvascular and macrovascular complications, suggesting a close mechanistic link between EPC dysfunction and impaired vascular function/repair in DM. These alterations to EPCs, likely mediated by multiple pathophysiological mechanisms, including inflammation, oxidative stress, and alterations in Akt and the nitric oxide pathway, affect EPCs at multiple stages: differentiation and mobilization in the bone marrow, trafficking and survival in the circulation, and homing and neovascularization. Several different therapeutic approaches have consequently been proposed to reverse the reduction and dysfunction of EPCs in DM and may represent a novel therapeutic approach to prevent and treat DM-related cardiovascular complications.

Emerging roles of hematopoietic cells in the pathobiology of diabetic complications

Diabetic complications encompass macrovascular events, mainly the result of accelerated atherosclerosis, and microvascular events that strike the eye (retinopathy), kidney (nephropathy), and nervous system (neuropathy). The traditional view is that hyperglycemia-induced dysregulated biochemical pathways cause injury and death of cells intrinsic to the organs affected. There is emerging evidence that diabetes compromises the function of the bone marrow (BM), producing a stem cell niche-dependent defect in hematopoietic stem cell mobilization. Furthermore, dysfunctional BM-derived hematopoietic cells contribute to diabetic complications. Thus, BM cells are not only a victim but also an accomplice in diabetes and diabetic complications. Understanding the underlying molecular mechanisms may lead to the development of new therapies to prevent and/or treat diabetic complications by specifically targeting these perpetrators.

A reappraisal of the role of circulating (progenitor) cells in the pathobiology of diabetic complications

Traditionally, the development of diabetic complications has been attributed to the biochemical pathways driving hyperglycaemic cell damage, while reparatory mechanisms have been long overlooked. A more comprehensive view of the balance between damage and repair suggests that an impaired regenerative capacity of bone marrow (BM)-derived cells strongly contributes to defective re-endothelisation and neoangiogenesis in diabetes. Although recent technological advances have redefined the biology and function of endothelial progenitor cells (EPCs), interest in BM-derived vasculotropic cells in the setting of diabetes and its complications remains high. Several circulating cell types of haematopoietic and non-haematopoietic origin are affected by diabetes and are potentially involved in the pathobiology of chronic complications. In addition to classical EPCs, these include circulating (pro-)angiogenic cells, polarised monocytes/macrophages (M1 and M2), myeloid calcifying cells and smooth muscle progenitor cells, having disparate roles in vascular biology. In parallel with the study of elusive progenitor cell phenotypes, it has been recognised that diabetes induces a profound remodelling of the BM stem cell niche. The alteration of circulating (progenitor) cells in the BM is now believed to be the link among distant end-organ complications. The field is rapidly evolving and interest is shifting from specific cell populations to the complex network of interactions that orchestrate trafficking of circulating vasculotropic cells.

Does drug therapy reverse endothelial progenitor cell dysfunction in diabetes?

Endothelial progenitor cells (EPCs) are vital for the maintenance and repair of the endothelium. Decreased EPC number and function have been associated with increased cardiovascular (CVD) risk. Patients with diabetes have decreased number of circulating EPCs and decreased EPC function. This may account for some of the increased CVD risk seen in patients with diabetes that is not explained by traditional risk factors such as glycemic control, dyslipidemia and hypertension. Recent studies seem to indicate that drugs commonly used in diabetes patients such as metformin, thiazolidinediones, GLP-1 agonists, DPP-4 inhibitors, insulin, statins and ACE inhibitors may increase EPC number and improve EPC function. The mechanisms by which these drugs modulate EPC function may involve reduction in inflammation, oxidative stress and insulin resistance as well as an increase in nitric oxide (NO) bioavailability. This review will discuss the evidence in the literature regarding the above mentioned topics.

Potential therapeutic use of deferoxamine and mesenchymal stem cells in type-1 diabetes: assembling another piece of the jigsaw, in what is a complex puzzle

Mesenchymal stem cells (MSCs) are recognized for their potential in regenerative medicine. Due to long-term negative effects associated with insulin administration and difficulty with pancreas transplantation, patients with type-1 diabetes could significantly benefit from organ-targeted cell-based therapy. Although several pharmacological agents increase the homing capacity of MSCs, the mechanisms regulating this process are still poorly understood. In this issue, Najafi et al. have demonstrated that pre-treatment of bone marrow-derived MSCs with the iron chelator and hypoxia mimetic, deferoxamine, can increase homing to the pancreas in a rat model of diabetes. This effect appears to be driven through specific chemokines in addition to hypoxia-inducing factor 1-alpha. Results from this study provide important clues in our endeavour to solve a complex process. Further studies will help determine whether these findings may offer potential therapeutic benefit to patients with diabetes.

Decreased levels and function of circulating endothelial progenitor cells in unruptured intracranial saccular aneurysm patients

Circulating endothelial progenitor cells (EPCs) play a critical role in maintaining endothelial integrity and keeping vascular homeostasis. Previously, we reported that EPCs were involved in repair and remodeling of aneurismal wall. In the present study, we verified this hypothesis by investigating the proliferative ability and count of EPCs in peripheral blood of patients with unruptured intracranial aneurysms (UIAs). Twenty-four patients with UIAs (UIA group) and 24 negative controls (control group) were included in this study. Peripheral blood monocytes (PBMCs) were harvested and selectively cultured. The colony-forming ability of cultured cells was analyzed and the biological functions were examined by testing the adsorption of ulex europaeus agglutinin-1 labeled by fluorescein isothiocyanate and acetylated low-density lipoprotein internalization. The migratory and adhesive ability of cultured EPCs were assessed. In vitro cultured PBMCs were identified as EPCs by examining surface markers CD34, CD133 and vascular endothelial growth factor receptor 2 using flow cytometry. EPCs from UIA group possessed significantly decreased proliferative, migratory and adhesive capacities compared with EPCs from control group. Furthermore, EPCs count in UIA group was significantly decreased. Collectively, these results indicated that the circulating EPCs of UIA patients may be involved in intracranial aneurysm repair and remodeling.