Endothelial progenitor cells in diabetes mellitus

Circulating endothelial progenitor cells in acromegaly

BACKGROUND

Endothelial progenitor cells (EPCs), involved in the repairing mechanisms of vascular damage, are positively correlated to insulin-like growth factor I (IGF-I) concentrations in healthy adults. However, the levels of EPCs and their role in acromegalic patients have never been investigated.

AIM

We conducted a cross-sectional study in order to assess the levels of the different phenotypes of circulating EPC in acromegalic patients.

SUBJECTS AND METHODS

The study was performed at the Endocrinology Unit of Federico II University and at the Unit of Metabolic Diseases and Endocrinology of the Second University of Naples. Fifty-five acromegalic patients and 65 healthy controls were studied. EPCs were assessed by flow cytometry and IGF-I by immunoradiometric assay.

RESULTS

Compared with subjects of the control group, acromegalic patients showed significantly higher levels of EPCs phenotypes expressing KDR antigen [KDR+, cells per 106 events, median and interquartile range, 44 (28-67) vs 23 (13-40), p=0.006; CD34+KDR+ 25 (18-38) vs 12 (8-17), p<0.001; CD133+KDR+ 17 (13-30) vs 8 (6-12), p<0.001; CD34+KDR+CD133+ 16 (12-25) vs 8 (6-10), p<0.001]. There was a positive correlations between CD34+KDR+CD133+ cells count and IGF-I in acromegaly group (r=0.79, p<0.001).

CONCLUSIONS

Acromegalic patients show higher circulating EPCs levels expressing KDR, positively correlated with IGF-I, suggesting a role for IGF-I in regulating the expression of this surface marker in the early phase of EPCs differentiation.

Cryopreservation and Enumeration of Human Endothelial Progenitor and Endothelial Cells for Clinical Trials

BACKGROUND

Endothelial progenitor cells (EPC) are markers of endothelial injury and may serve as a surrogate marker for vascular repair in interventional clinical trials. Objectives of this study were to modify a method of isolation of peripheral blood mononuclear cells (PBMC) and enumeration of EPC and mature endothelial cells (EC) from peripheral blood and to evaluate influence of cryopreservation on viability of PBMC and on numbers of EPC and EC.

PATIENTS/METHODS

EPC and EC were analyzed in healthy volunteers in freshly isolated PBMC collected in CPT (cell preparation tubes) and in PBMC cryopreserved with: 1) Gibco Recovery™ Cell Culture Freezing Medium, 2) custom freezing medium. Viability of PBMC was tested using DAPI. EPC were gated for CD45- CD34+CD133+/-VEGFR2+/- and EC were gated for CD45-CD146+CD34+/-VEGFR2+/-.

RESULTS

Cryopreservation for 7 days at -80°C decreased viable PBMC from 94 ± 0.5% (fresh) to 84 ± 4% (the custom medium) and to 69 ± 8% (Gibco medium), while cryopreservation at -65°C decreased viability to 60 ± 6% (p<0.001, the custom medium) and 49 ± 5% (p<0.001, Gibco medium). In fresh samples early EPC (CD45- CD34+CD133+VEGFR2+) were enumerated as 0.2 ± 0.06%, late EPC(CD45-CD146+CD34+VEGFR2+) as 0.6 ± 0.1% and mature EC (CD45-CD146+CD34-VEGFR2+) as 0.8 ± 0.3%of live PBMC. Cryopreservation with Gibco and the custom freezing medium at -80°C for 7 days decreased numbers EPC and EC, however, this decrease was not statistically significant.

CONCLUSIONS

Our data indicate that cryopreservation at -80°C for 7 days decreases, although not significantly, viability of PBMC and numbers of subsets of EC and EPC. This method may provide an optimized approach to isolation and short-term cryopreservation of subsets of EPC and of mature EC suitable for multicenter trials.

Dysglycaemia, vasculopenia, and the chronic consequences of diabetes

High glucose concentrations are independent risk factors for many serious disorders. Glucose lowering can reduce or prevent many of these disorders. The mechanisms that cause glucose-linked tissue damage are unclear; however, the sequence of tissue changes that lead to one of these consequences (ie, retinopathy) have been understood for decades because the retina can be easily inspected and changes in its vascular supply can easily be assessed. The possibility that the long-term harms of raised glucose concentrations are mediated through reduced capillary perfusion (ie, vasculopenia) is suggested by strong epidemiological links between capillary abnormalities in the retina and most of the complications of diabetes, a delay between the therapeutic effect of glucose lowering in the retina and in other tissues, laboratory evidence that atherosclerosis is promoted by abnormalities in the capillary-rich vasa vasorum of conductance vessels, and similarities in capillary abnormalities in the retina and the kidney of people with diabetes. These findings also suggest that the retina might be a window through which the effect of raised glucose concentrations on a wide range of tissues can be seen. If continuing research lends support to this theory, treatments that counteract the effect of glucose on capillaries such as those in the retina might ultimately also reduce other serious consequences of dysglycaemia.

Biomolecular basis of the role of diabetes mellitus in osteoporosis and bone fractures

Osteoporosis has become a serious health problem throughout the world which is associated with an increased risk of bone fractures and mortality among the people of middle to old ages. Diabetes is also a major health problem among the people of all age ranges and the sufferers due to this abnormality increasing day by day. The aim of this review is to summarize the possible mechanisms through which diabetes may induce osteoporosis. Diabetes mellitus generally exerts its effect on different parts of the body including bone cells specially the osteoblast and osteoclast, muscles, retina of the eyes, adipose tissue, endocrine system specially parathyroid hormone (PTH) and estrogen, cytokines, nervous system and digestive system. Diabetes negatively regulates osteoblast differentiation and function while positively regulates osteoclast differentiation and function through the regulation of different intermediate factors and thereby decreases bone formation while increases bone resorption. Some factors such as diabetic neuropathy, reactive oxygen species, Vitamin D, PTH have their effects on muscle cells. Diabetes decreases the muscle strength through regulating these factors in various ways and ultimately increases the risk of fall that may cause bone fractures.

Enhanced growth of endothelial precursor cells on PCG-matrix facilitates accelerated, fibrosis-free, wound healing: a diabetic mouse model

Diabetes mellitus (DM)-induced endothelial progenitor cell (EPC) dysfunction causes impaired wound healing, which can be rescued by delivery of large numbers of 'normal' EPCs onto such wounds. The principal challenges herein are (a) the high number of EPCs required and (b) their sustained delivery onto the wounds. Most of the currently available scaffolds either serve as passive devices for cellular delivery or allow adherence and proliferation, but not both. This clearly indicates that matrices possessing both attributes are 'the need of the day' for efficient healing of diabetic wounds. Therefore, we developed a system that not only allows selective enrichment and expansion of EPCs, but also efficiently delivers them onto the wounds. Murine bone marrow-derived mononuclear cells (MNCs) were seeded onto a PolyCaprolactone-Gelatin (PCG) nano-fiber matrix that offers a combined advantage of strength, biocompatibility wettability; and cultured them in EGM2 to allow EPC growth. The efficacy of the PCG matrix in supporting the EPC growth and delivery was assessed by various in vitro parameters. Its efficacy in diabetic wound healing was assessed by a topical application of the PCG-EPCs onto diabetic wounds. The PCG matrix promoted a high-level attachment of EPCs and enhanced their growth, colony formation, and proliferation without compromising their viability as compared to Poly L-lactic acid (PLLA) and Vitronectin (VN), the matrix and non-matrix controls respectively. The PCG-matrix also allowed a sustained chemotactic migration of EPCs in vitro. The matrix-effected sustained delivery of EPCs onto the diabetic wounds resulted in an enhanced fibrosis-free wound healing as compared to the controls. Our data, thus, highlight the novel therapeutic potential of PCG-EPCs as a combined 'growth and delivery system' to achieve an accelerated fibrosis-free healing of dermal lesions, including diabetic wounds.

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.

Increase of palmitic acid concentration impairs endothelial progenitor cell and bone marrow-derived progenitor cell bioavailability: role of the STAT5/PPARγ transcriptional complex

Metabolic profiling of plasma nonesterified fatty acids discovered that palmitic acid (PA), a natural peroxisome proliferator-activated receptor γ (PPARγ) ligand, is a reliable type 2 diabetes biomarker. We investigated whether and how PA diabetic (d-PA) concentrations affected endothelial progenitor cell (EPC) and bone marrow-derived hematopoietic cell (BM-HC) biology. PA physiologic (n-PA) and d-PA concentrations were used. Proliferating cell nuclear antigen content and signal transducer and activator of transcription 5 (STAT5), PPARγ, cyclin D1, and p21(Waf) expression were evaluated. Small interfering RNA technology, gene reporter luciferase assay, electrophoretic mobility shift assay, chromatin immunoprecipitation assay, and coimmunoprecipitation were exploited. In vivo studies and migration assays were also performed. d-PA, unlike n-PA or physiological and diabetic oleic and stearic acid concentrations, impaired EPC migration and EPC/BM-HC proliferation through a PPARγ-mediated STAT5 transcription inhibition. This event did not prevent the formation of a STAT5/PPARγ transcriptional complex but was crucial for gene targeting, as p21(Waf) gene promoter, unlike cyclin D1, was the STAT5/PPARγ transcriptional target. Similar molecular events could be detected in EPCs isolated from type 2 diabetic patients. By expressing a constitutively activated STAT5 form, we demonstrated that STAT5 content is crucial for gene targeting and EPC fate. Finally, we also provide in vivo data that d-PA-mediated EPC dysfunction could be rescued by PPARγ blockade. These data provide first insights on how mechanistically d-PA drives EPC/BM-HC dysfunction in diabetes.

Review: Endothelial progenitor cells in pregnancy and obstetric pathologies

Since their discovery, endothelial progenitor cells (EPCs) have generated considerable interest in vascular biology. They are a heterogeneous population of cells that exist in both the fetus and adult, and are mobilized to support de novo vessel formation or encourage vascular health. This review summarizes our understanding of these cells in pregnancy, paying particular attention to their physiological role in placental development and the uterus, alongside their involvement in related obstetric pathologies.

Restoring stem cell mobilization to promote vascular repair in diabetes

Diabetes triggers endothelial dysfunction, which is linked to increased risk of cardiovascular diseases. Stem and progenitor cells from the bone marrow are involved in the maintenance of vascular integrity. Diabetic patients show a dysfunction of these cells, which might represent a novel pathophysiological mechanism of vascular disease. Specifically, stem and progenitor cells fail to egress from the bone marrow (BM) due to BM pathological alterations and unresponsiveness to mobilizing stimuli. In this review, we describe impaired stem cell mobilization in diabetes as a mechanism of failed vascular repair and we provide evidence that pharmacological strategies can restore mobilization. We discuss recent advances in the knowledge of aberrant organization of the diabetic BM and its implications for impaired mobilization. Finally, we describe in detail the pharmacological exploitation of the G-CSF/DPP-4(CD26)/SDF-1α axis as a novel strategy to improve mobilization and attain vascular repair in diabetes.

Worse clinical outcomes in acute myocardial infarction patients with type 2 diabetes mellitus: relevance to impaired endothelial progenitor cells mobilization

Background

Although the clinical outcome of acute myocardial infarction (AMI) in patients with type 2 diabetes mellitus (T2DM) is well established to be worse than for non-diabetic patients, the reasons for this remain unclear. We hypothesized that this may be related to impairment of bone marrow-derived endothelial progenitor cells (EPCs) mobilization.

Methodology/Principal Findings

We observed short term bone marrow EPCs mobilization and long term clinical outcomes in 62 AMI patients with or without T2DM and investigated EPCs levels as well as bone marrow pathway changes in a rat model of diabetes after AMI. Patients with T2DM exhibited a delay (peak time diabetics vs. non-diabetics: day 7 vs. day 5) and a decrease in EPCs mobilization (diabetics vs. non-diabetics: 285±56/10⁶ mononuclear cells (MNCs) vs. 431±88/10⁶ MNCs, p<0.05) within one month after AMI. Plasma levels of VEGF and SDF-1α as well as of hsCRP were higher in T2DM patients. Over a mean of 2.26 years follow-up, T2DM patients exhibited a pronounced decrease in LVEF as well as an increase in clinical events. Glucose (HR 2.01, 95% CI 1.42–2.85, p = 0.008), first day EPC (HR 0.974, 95% CI 0.952–0.997, p = 0.02) and seven day EPCs (HR 0.966, 95% CI 0.945–0.988, p = 0.003) were independent prognostic variables for cardiovascular mortality. In a diabetic rat model of AMI, decreased circulating EPCs was accompanied by lower expression of phospho-Akt, phospho-eNOS, HIF, MMP-9 and MMP-9 activity in the bone marrow as well as impaired cardiac function, angiogenesis and increased left ventricle remodeling.

Conclusions/Significance

Bone marrow EPCs mobilization is delayed and reduced in diabetes, with impaired HIF/p-Akt/p-eNOS/MMP-9 signaling. This is likely to contribute to the deterioration in cardiac function and worsened clinical outcome seen in patients with T2DM.

A diseased bone marrow fuels atherosclerosis in diabetes

Diabetes accelerates atherosclerosis through shortage of vascular regenerative cells derived from the bone marrow (BM). In addition, diabetes shifts the differentiation of BM progenitor cells to pro-calcific and smooth muscle phenotypes. In a paper published in Atherosclerosis, Fledderus et al. demonstrate that the accelerated atherosclerosis in diabetic ApoE(-/-) mice is associated with an increased amount of BM-derived smooth muscle cells in the plaques. The role of ApoE in the regulation of vascular BM progenitors may explain inconsistencies in the literature on the contribution of extraparietal cells to atherosclerotic lesions. Herein, the pathophysiological meaning of a deranged kinetic of smooth muscle progenitor cells in diabetes is discussed.

The small MAF transcription factors MAFF, MAFG and MAFK: current knowledge and perspectives

The small MAFs, MAFF, MAFG and MAFK have emerged as crucial regulators of mammalian gene expression. Previous studies have linked small MAF function, by virtue of their heterodimerization with the Cap 'n' Collar (CNC) family of transcription factors, to the stress response and detoxification pathways. Recent analyses have revealed a complex regulatory network involving small MAF transcription factors and other cellular proteins. The expression and activity of small MAFs are tightly regulated at multiple levels. With regard to their clinical importance, small MAFs have been linked to various diseases, such as diabetes, neuronal disorders, thrombocytopenia and carcinogenesis. A better understanding of the molecular mechanisms governing the activity of small MAFs will provide novel insights into the control of mammalian transcription and may lead to the development of novel therapeutic strategies to treat common human disorders.