Glucose tolerance is negatively associated with circulating progenitor cell levels

Gemigliptin, a potent selective dipeptidyl peptidase 4 inhibitor, protects endothelial progenitor cells by oxidative stress via caspase-3 dependent pathway

Endothelial progenitor cells (EPCs) are exclusive players in vasculogenesis and endothelial regeneration. EPCs are of two types and their differentiation is mediated by different growth factors. A decrease in EPC number and function causes cardiovascular abnormalities and reduced angiogenesis. Various studies has documented a role of EPCs in diabetes. EPCs treatment with different drugs improve insulin secretion but causes other abnormalities. In vivo and in vitro studies have reported anti glycation effect of gemigliptin but no data is available on in vitro effect of gemigliptin on EPC number and functional credibility. The current study was aimed to find an in vitro effect of gemigliptin on EPC number and function along with an effective treatment dose of gemigliptin. EPCs were isolated, cultured and phenotypically characterized using Dil- AcLDL and ulex-lectin fluorescence staining. EPCs were then treated with different doses of Zemiglo and their viability analyzed with viability assay using water-soluble tetrazolium salt (WST-1), by Annexin V and Propidium Iodide (PI) staining, senescence-associated beta-galactosidase (SA-β-gal) staining, western blot and Flow cytometric analysis of apoptotic signals. The results demonstrated that the isolated EPCs has typical endothelial phenotypes. And these EPCs were of two types based on morphology i.e., early and late EPCs. Gemigliptin dose dependently improved the EPCs morphology and increased EPCs viability, the most effective dose being the 20 μM. Gemigliptin at 10 μM, 20 μM and 50 μM significantly increased the BCL-2 levels and at 20 μM significantly decreased the Caspase-3 levels in EPCs. In conclusion, gemigliptin dose dependently effects the EPCs viability and morphology through Caspase-3 signaling. Our results are the first report of gemigliptin effect on EPC viability and morphology.

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.

A novel therapeutic management for diabetes patients with chronic limb-threatening ischemia: comparison of autologous bone marrow mononuclear cells versus allogenic Wharton jelly-derived mesenchymal stem cells

BACKGROUND

Chronic limb-threatening ischemia (CLTI) represents the final stage of peripheral arterial disease. Approximately one-third of patients with CLTI are not eligible for conventional surgical treatments. Furthermore, patients with advanced stage of CLTI are prone to amputation and death. Thus, an effective therapeutic strategy is urgently needed. In this context, autologous bone marrow mononuclear cell (auto-BM-MNC) and allogeneic mesenchymal stem cells represent a promising therapeutic approach for treating CLTI. In this study, we compared the safety and beneficial therapeutic effect of auto-BM-MNC versus allogeneic Wharton jelly-derived mesenchymal stem cells (allo-WJ-MSCs) in diabetic patients with CLTI.

METHODS

We performed a randomized, prospective, double-blind and controlled pilot study. Twenty-four diabetic patients in the advanced stage of CLTI (4 or 5 in Rutherford's classification) and a transcutaneous oxygen pressure (TcPO2) below 30 mmHg were randomized to receive 15 injections of (i) auto-BM-MNC (7.197 × 106 ± 2.984 × 106 cells/mL) (n = 7), (ii) allo-WJ-MSCs (1.333 × 106 cells/mL) (n = 7) or (iii) placebo solution (1 mL) (n = 10), which were administered into the periadventitial layer of the arterial walls under eco-Doppler guidance. The follow-up visits were at months 1, 3, 6, and 12 to evaluate the following parameters: (i) Rutherford's classification, (ii) TcPO2, (iii) percentage of wound closure, (iv) pain, (v) pain-free walking distance, (vi) revascularization and limb-survival proportion, and (vii) life quality (EQ-5D questionnaire).

RESULTS

No adverse events were reported. Patients with CLTI who received auto-BM-MNC and allo-WJ-MSCs presented an improvement in Rutherford's classification, a significant increase in TcPO2 values‬, a reduction in the lesion size in a shorter time, a decrease in the pain score and an increase in the pain-free walking distance, in comparison with the placebo group. In addition, the participants treated with auto-BM-MNC and allo-WJ-MSCs kept their limbs during the follow-up period, unlike the placebo group, which had a marked increase in amputation.

CONCLUSIONS

Our results showed that patients with CLTI treated with auto-BM-MNC and allo-WJ-MSCs conserved 100% of their limb during 12 months of the follow-up compared to the placebo group, where 60% of participants underwent limb amputation in different times. Furthermore, we observed a faster improvement in the allo-WJ-MSC group, unlike the auto-BM-MNC group. Trial registration This study was retrospectively registered at ClinicalTrials.gov (NCT05631444).

Effects of Early Intensive Insulin Therapy on Endothelial Progenitor Cells in Patients with Newly Diagnosed Type 2 Diabetes

AIM

This study aimed to investigate the alteration of circulating CD34⁺KDR⁺CD133⁺ endothelial progenitor cells (EPCs) in patients with newly diagnosed type 2 diabetes and the mechanism of the effect of early intensive insulin therapy.

METHODS

In this study, 36 patients with newly diagnosed type 2 diabetes and 22 control subjects matched by age and gender were enrolled. All of the patients with diabetes received intensive insulin therapy. The number of EPCs was assessed by flow cytometry based on the expression of CD34, CD133, and kinase insert domain-containing receptor (KDR).

RESULTS

Levels of circulating CD34⁺KDR⁺CD133⁺ EPCs were higher in patients with diabetes compared to control subjects and significantly decreased after intensive insulin therapy. Levels of vascular endothelial growth factor (VEGF), a major contributor to EPC mobilization, were significantly higher in patients with diabetes compared to control subjects, and dramatically decreased after insulin therapy. Importantly, VEGF levels correlated with number of EPCs. Moreover, compared with control subjects, pro-inflammatory cytokines and oxidative stress were significantly higher in patients with diabetes and markedly decreased after intensive insulin therapy.

CONCLUSIONS

These results showed that type 2 diabetes is associated with an increase of circulating CD34⁺KDR⁺CD133⁺ EPCs at the onset of diabetes, indicating increased compensatory mobilization. Additionally, early intensive insulin therapy exerts a preserving effect on EPC level partly through improving inflammation status and oxidative stress, thereby implying a putative long-term beneficial effect on vascular integrity via suspending excessive EPC exhaustion.

CLINICAL TRIAL NUMBER

NCT03710811.

Plasma Lipid Profiling Contributes to Untangle the Complexity of Moyamoya Arteriopathy

Moyamoya arteriopathy (MA) is a rare cerebrovascular disorder characterized by ischemic/hemorrhagic strokes. The pathophysiology is unknown. A deregulation of vasculogenic/angiogenic/inflammatory pathways has been hypothesized as a possible pathophysiological mechanism. Since lipids are implicated in modulating neo-vascularization/angiogenesis and inflammation, their deregulation is potentially involved in MA. Our aim is to evaluate angiogenic/vasculogenic/inflammatory proteins and lipid profile in plasma of MA patients and control subjects (healthy donors HD or subjects with atherosclerotic cerebrovascular disease ACVD). Angiogenic and inflammatory protein levels were measured by ELISA and a complete lipidomic analysis was performed on plasma by mass spectrometry. ELISA showed a significant decrease for MMP-9 released in plasma of MA. The untargeted lipidomic analysis showed a cumulative depletion of lipid asset in plasma of MA as compared to HD. Specifically, a decrease in membrane complex glycosphingolipids peripherally circulating in MA plasma with respect to HD was observed, likely suggestive of cerebral cellular recruitment. The quantitative targeted approach demonstrated an increase in free sphingoid bases, likely associated with a deregulated angiogenesis. Our findings indicate that lipid signature could play a central role in MA and that a detailed biomarker profile may contribute to untangle the complex, and still obscure, pathogenesis of MA.

Endothelial Progenitor Cells: An Appraisal of Relevant Data from Bench to Bedside

The mobilization of endothelial progenitor cells (EPCs) into circulation from bone marrow is well known to be present in several clinical settings, including acute coronary syndrome, heart failure, diabetes and peripheral vascular disease. The aim of this review was to explore the current literature focusing on the great opportunity that EPCs can have in terms of regenerative medicine.

Altered Frequency and Phenotype of HLA-G-Expressing DC-10 in Type 1 Diabetes Patients at Onset and in Subjects at Risk to Develop the Disease

Type 1 diabetes (T1D) is a chronic autoimmune disease resulting in progressive destruction of β-cells. Several factors affecting lymphocyte and antigen-presenting cells, including dendritic cells (DCs), contribute to defective maintenance of tolerance in T1D. DC-10 are a subset of human DCs involved in IL-10-mediated tolerance. A precise monitoring of DC-10 in the peripheral blood is possible thanks to the discovery of specific biomarkers. DC-10, being cells that naturally express HLA-G, may be used for the appropriate staging of the disease. By enumerating and phenotypically characterizing DC-10 in the peripheral blood of subjects at different stages of T1D development-first-degree relatives (FDRs) of T1D patients, without (Abneg) or with (Abpos) autoantibodies, T1D patients at onset, and age-matched healthy controls (HCs)-we showed that DC-10 contain a high proportion of HLA-G-expressing cells as compared with monocytes. We reported that a low frequency of DC-10 during disease development is paralleled with the increased proportion of pro-inflammatory cDC2 cells. Moreover, DC-10 number and phenotype differ from Abneg FDRs, Abpos FDRs, and T1D patients compared with HCs, and DC-10 from T1D patients express low levels of CD83. Finally, multiple regression analysis, considering DC-10 and HLA-G-related parameters, showed that Abneg FDRs are more similar to subjects with autoimmunity than to HCs. This is the first demonstration that impairment in DC-10 number and phenotype, specifically CD83 expression, is associated with risk of developing T1D, suggesting a possible use of CD83+ DC-10 to stratify individuals at risk of T1D in conjunction with classical prognostic factors.

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.

Vascular Remodeling in Moyamoya Angiopathy: From Peripheral Blood Mononuclear Cells to Endothelial Cells

The pathophysiological mechanisms of Moyamoya angiopathy (MA), which is a rare cerebrovascular condition characterized by recurrent ischemic/hemorrhagic strokes, are still largely unknown. An imbalance of vasculogenic/angiogenic mechanisms has been proposed as one possible disease aspect. Circulating endothelial progenitor cells (cEPCs) have been hypothesized to contribute to vascular remodeling of MA, but it remains unclear whether they might be considered a disease effect or have a role in disease pathogenesis. The aim of the present study was to provide a morphological, phenotypical, and functional characterization of the cEPCs from MA patients to uncover their role in the disease pathophysiology. cEPCs were identified from whole blood as CD45^dimCD34⁺CD133⁺ mononuclear cells. Morphological, biochemical, and functional assays were performed to characterize cEPCs. A significant reduced level of cEPCs was found in blood samples collected from a homogeneous group of adult (mean age 46.86 ± 11.7; 86.36% females), Caucasian, non-operated MA patients with respect to healthy donors (HD; p = 0.032). Since no difference in cEPC characteristics and functionality was observed between MA patients and HD, a defective recruitment mechanism could be involved in the disease pathophysiology. Collectively, our results suggest that cEPC level more than endothelial progenitor cell (EPC) functionality seems to be a potential marker of MA. The validation of our results on a larger population and the correlation with clinical data as well as the use of more complex cellular model could help our understanding of EPC role in MA pathophysiology.

Reduced Circulating Endothelial Progenitor Cells and Downregulated GTCPH I Pathway Related to Endothelial Dysfunction in Premenopausal Women with Isolated Impaired Glucose Tolerance

Background

Individuals at a prediabetic stage have had an augmented cardiovascular disease (CVD) risk and CVD-related mortality compared to normal glucose tolerance (NGT) individuals, which may be attributed to the impaired vascular endothelial repair capacity. In this study, circulating endothelial progenitor cells' (EPCs) number and activity were evaluated, and the underlying mechanisms in premenopausal women with impaired glucose regulation were explored.

Methods

Circulating EPCs' number and activity and flow-mediated dilation (FMD) were compared in premenopausal women with NGT, isolated impaired fasting glucose (i-IFG), or isolated impaired glucose tolerance (i-IGT). Plasma nitric oxide (NO), EPCs-secreted NO, and intracellular BH4 levels were also measured. The key proteins (Tie2, Akt, eNOS, and GTPCH I) in the guanosine triphosphate cyclohydrolase/tetrahydrobiopterin (GTPCH/BH4) pathway and Tie2/Akt/eNOS signaling pathway were evaluated in these women.

Results

It was observed that the i-IGT premenopausal women not i-IFG premenopausal women had a significant reduction in circulating EPCs' number and activity as well as reduced FMD when compared to NGT subjects. Plasma NO levels or EPCs-secreted NO also decreased only in i-IGT women. The expression of GTCPH I as well as intracellular BH4 levels declined in i-IGT women; however, the alternations of key proteins' expression in the Tie2/Akt/eNOS signaling pathway were not observed in either i-IGT or i-IFG women.

Conclusions

The endothelial repair capacity was impaired in i-IGT premenopausal women but was preserved in i-IFG counterparts. The underlying mechanism may be associated with the downregulated GTCPH I pathway and reduced NO productions.

Endothelium-Derived Factors Influence Differentiation of Fat-Derived Stromal Cells Post-Exercise in Subjects with Prediabetes

Purpose: We investigated the effect of aerobic and resistance exercise on abdominal subcutaneous fat-derived stromal cells in middle-aged subjects with prediabetes, pre- and post-exercise to establish molecular mechanisms that drive the effect of exercise. Methods: Five subjects, aged between 40 and 60 years with a body mass index between 25 and 39.9 kg/m² and with prediabetes, were enrolled in a 12-week exercise intervention program. Biophysical parameters were assessed pre- and post-exercise. Stromal cells were obtained from subcutaneous abdominal fat and cultured for 2-3 weeks. The stromal cells were then analyzed for mRNA analysis pre- and post-exercise. This was followed up with in vitro experiments where commercially obtained human fat-derived mesenchymal stromal cells (MSCs) were exposed to adipogenic media, and conditioned media from human endothelial conditioned media (ECM) cells were added to note if ECM addition altered adipogenesis. Subsequently, MSC differentiation was monitored by reverse transcription-polymerase chain reaction (RT-PCR). Results: Post-exercise, subjects' cardiometabolic parameters improved. MSC obtained at post-exercise phase, from subcutaneous fat biopsies, on RT-PCR analysis, showed upregulation of antioxidant, mitochondrial, glucose transporter, and genes associated with osteogenesis compared with pre-exercise MSC mRNA. A concomitant increase in plasma osteocalcin levels was also noted post-exercise. In vitro, MSCs exposed to adipogenic differentiation media with the addition of ECM showed a significant reduction in expression of adipogenic marker genes and instead showed upregulation of genes associated with osteogenic differentiation. Conclusions: Exercise appears to prevent adipogenic differentiation of fat-derived stromal cells and promote osteogenic differentiation, in prediabetic middle-aged subjects. Interestingly, the addition of endothelium-derived factors to adipogenic media also appears to prevent adipogenic differentiation of commercially obtained fat-derived stromal cells and promotes osteogenic differentiation. Both in vivo and in vitro findings emphasize the paracrine effect of endothelium-derived factors on fat differentiation.

Exercise and Cardiovascular Progenitor Cells

Autologous stem/progenitor cell-based methods to restore blood flow and function to ischemic tissues are clinically appealing for the substantial proportion of the population with cardiovascular diseases. Early preclinical and case studies established the therapeutic potential of autologous cell therapies for neovascularization in ischemic tissues. However, trials over the past ∼15 years reveal the benefits of such therapies to be much smaller than originally estimated and a definitive clinical benefit is yet to be established. Recently, there has been an emphasis on improving the number and function of cells [herein generally referred to as circulating angiogenic cells (CACs)] used for autologous cell therapies. CACs include of several subsets of circulating cells, including endothelial progenitor cells, with proangiogenic potential that is largely exerted through paracrine functions. As exercise is known to improve CV outcomes such as angiogenesis and endothelial function, much attention is being given to exercise to improve the number and function of CACs. Accordingly, there is a growing body of evidence that acute, short-term, and chronic exercise have beneficial effects on the number and function of different subsets of CACs. In particular, recent studies show that aerobic exercise training can increase the number of CACs in circulation and enhance the function of isolated CACs as assessed in ex vivo assays. This review summarizes the roles of different subsets of CACs and the effects of acute and chronic exercise on CAC number and function, with a focus on the number and paracrine function of circulating CD34+ cells, CD31+ cells, and CD62E+ cells. © 2019 American Physiological Society. Compr Physiol 9:767-797, 2019.

Green Tea Polyphenol Epigallocatechin-3-Gallate Promotes Reendothelialization in Carotid Artery of Diabetic Rabbits by Reactivating Akt/eNOS Pathway

Background: Epigallocatechin gallate (EGCG) is the most abundant catechin in green tea and has proven benefits on endothelial cells in diabetes. However, it remains unclear whether EGCG could improve function of late endothelial progenitor cells (L-EPCs) in diabetes.

Methods: Thirty-six rabbits were randomized into six groups. Thirty diabetic rabbits were induced by a single dose of alloxan (100 mg/kg injection intraperitoneally). All of them were given intragastrically EGCG (50 mg/kg/day) or saline for 7 days after carotid injury. In autotransfusion experiment, L-EPCs were cultured with pre-treated EGCG (40 μM for 72 h) and then were injected into the site of injured vascular. Proliferation and migration of EGCG pre-treated L-EPCs in high glucose condition were assessed by EDU incorporation assay and modified Boyden chamber assay, respectively. The mRNA and protein expression of Akt-eNOS pathway were detected by real-time PCR and western blot.

Results: Reendothelialization rate in injured carotid artery of diabetic rabbits was augmented in the EGCG group (50 mg/kg/d for 7 days) compared with the non-EGCG group (74.2 ± 4.6% vs. 25.6 ± 5.9%, P < 0.001). EGCG pre-treated L-EPCs autologous transfusion also accelerated the diabetic rabbits’ carotid reendothelialization compared with the diabetic sham-operated group (65.6 ± 8.5% vs. 32.9 ± 5.0%, P = 0.011). In vitro studies showed, 40 μM EGCG treatment for 72 h recovered L-EPCs’ proliferation and migration, as well as restored the phosphorylation level of Akt and eNOS blocked by high glucose condition.

Conclusion: EGCG accelerated reendothelialization in diabetic rabbits after carotid injury in part by reactivating the Akt/eNOS pathway, which might contribute to recovering proliferation and migration of L-EPCs impaired by high glucose.

Cardiac mesenchymal cells from diabetic mice are ineffective for cell therapy-mediated myocardial repair

Although cell therapy improves cardiac function after myocardial infarction, highly variable results and limited understanding of the underlying mechanisms preclude its clinical translation. Because many heart failure patients are diabetic, we examined how diabetic conditions affect the characteristics of cardiac mesenchymal cells (CMC) and their ability to promote myocardial repair in mice. To examine how diabetes affects CMC function, we isolated CMCs from non-diabetic C57BL/6J (CMCWT) or diabetic B6.BKS(D)-Leprdb/J (CMCdb/db) mice. When CMCs were grown in 17.5 mM glucose, CMCdb/db cells showed > twofold higher glycolytic activity and a threefold higher expression of Pfkfb3 compared with CMCWT cells; however, culture of CMCdb/db cells in 5.5 mM glucose led to metabolic remodeling characterized by normalization of metabolism, a higher NAD+/NADH ratio, and a sixfold upregulation of Sirt1. These changes were associated with altered extracellular vesicle miRNA content as well as proliferation and cytotoxicity parameters comparable to CMCWT cells. To test whether this metabolic improvement of CMCdb/db cells renders them suitable for cell therapy, we cultured CMCWT or CMCdb/db cells in 5.5 mM glucose and then injected them into infarcted hearts of non-diabetic mice (CMCWT, n = 17; CMCdb/db, n = 13; Veh, n = 14). Hemodynamic measurements performed 35 days after transplantation showed that, despite normalization of their properties in vitro, and unlike CMCWT cells, CMCdb/db cells did not improve load-dependent and -independent parameters of left ventricular function. These results suggest that diabetes adversely affects the reparative capacity of CMCs and that modulating CMC characteristics via culture in lower glucose does not render them efficacious for cell therapy.

Influence of high density lipoprotein cholesterol levels on circulating monocytic angiogenic cells functions in individuals with type 2 diabetes mellitus

Background

High-density lipoproteins (HDLs) can exert anti-atherogenic effects. On top of removing excess cholesterol through reverse cholesterol transport, HDLs play beneficial actions on endothelial function and integrity. In particular, HDLs are strong determinant of endothelial progenitor cells (EPCs) number and function. To gain further insights into such an effect we characterized in vitro functionality of circulating “early” EPCs obtained from 60 type 2 diabetes individuals with low HDL-cholesterol (HDL-C) and 59 with high HDL-C levels.

Methods

After an overnight fast, venous blood was drawn in EDTA tubes and processed within 2-h from sampling. Peripheral blood mononuclear cells were isolated and plated on fibronectin coated culture dishes; after 3 days culture, adherent cells positive for Dil-ac-LDL/Lectin dual fluorescent staining were identified as monocytic angiogenic cells (MACs). After 5–7 days culture in EBM-2 medium, adherent cells were evaluated for viability/proliferation (MTT assay), senescence (beta-galactosidase activity detection), migration (modified Boyden chamber using VEGF as chemoattractant), adhesion capacity (on fibronectin-coated culture dishes) and ROS production (ROS-sensitive fluorescent probe CM-H₂DCFDA).

Results

MACs obtained from diabetic individuals with high HDL-C had 23% higher viability compared to low HDL-C (111.6 ± 32.7% vs. 90.5 ± 28.6% optical density; p = 0.002). H₂O₂ exposure impaired MACs viability to a similar extent in both groups (109.2 ± 31.7% vs. 74.5 ± 40.8% in high HDL-C, p < 0.0001; 88.3 ± 25.5% vs. 72.3 ± 22.5% in low-HDL, p = 0.004). MACs senescence was comparable in the two groups (102.7 ± 29.8% vs. 99.2 ± 27.8%; p = 0.703) and was only slightly modified by exposure to H₂O₂. There was no difference in the MACs migration capacity between the two groups (91.3 ± 34.2% vs. 108.7 ± 39.5%; p = 0.111), as well as in MACs adhesion capacity (105.2 ± 32.7% vs. 94.1 ± 26.1%; p = 0.223). Finally, ROS production was slightly thought not significantly higher in MACs from type 2 diabetes individuals with low- than high-HDL. After stratification of HDL-C levels into quartiles, viability (p < 0.0001) and adhesion (p = 0.044) were higher in Q4 than in Q1–Q3. In logistic regression analysis, HDL-C was correlated to MACs viability and adhesion independently of HbA1c or BMI, respectively.

Conclusions

Our data suggest that in type 2 diabetes subjects, HDL-cholesterol is an independent determinant of circulating MACs functional capacities—mainly viability, to a lesser extent adhesion—likely contributing also through this mechanism to cardiovascular protection even in type 2 diabetes.

The synergistic effects of saxagliptin and metformin on CD34+ endothelial progenitor cells in early type 2 diabetes patients: a randomized clinical trial

AIMS

Type 2 diabetes is associated with endothelial dysfunction leading to cardiovascular disease. CD34+ endothelial Progenitor Cells (EPCs) are responsible for endothelial repair and neo-angiogenesis and can be used as a cardiovascular disease risk biomarker. This study investigated whether the addition of saxagliptin, a DPP-IV inhibitor, to metformin, may reduce cardiovascular disease risk in addition to improving glycemic control in Type 2 diabetes patients.

METHODS

In 12 week, double-blind, randomized placebo-controlled trial, 42 subjects already taking metformin 1-2 grams/day were randomized to placebo or saxagliptin 5 mg. Subjects aged 40-70 years with diabetes for < 10 years, with no known cardiovascular disease, BMI 25-39.9, HbA1C 6-9% were included. We evaluated EPCs number, function, surface markers and gene expression, in addition to arterial stiffness, blood biochemistries, resting energy expenditure, and body composition parameters. A mixed model regression to examine saxagliptin vs placebo, accounting for within-subject autocorrelation, was done with SAS (p < 0.05).

RESULTS

Although there was no significant increase in CD34+ cell number, CD31+ cells percentage increased. Saxagliptin increased migration (in response to SDF1α) with a trend of higher colony formation count. MNCs cytometry showed higher percentage of CXCR4 double positivity for both CD34 and CD31 positive cells, indicating a functional improvement. Gene expression analysis showed an upregulation in CD34+ cells for antioxidant SOD1 (p < 0.05) and a downregulation in CD34- cells for IL-6 (p < 0.01). For arterial stiffness, both augmentation index and systolic blood pressure measures went down in saxagliptin subjects (p < 0.05).

CONCLUSION

Saxagliptin, in combination with metformin, can help improve endothelial dysfunction in early diabetes before macrovascular complications appear. Trial registration Trial is registered under clinicaltrials.gov, NCT02024477.

Decreased diabetes risk over 9 year after 18-month oral L-arginine treatment in middle-aged subjects with impaired glucose tolerance and metabolic syndrome (extension evaluation of L-arginine study)

Purpose

This study aimed to determine whether l-arginine supplementation lasting for 18 months maintained long-lasting effects on diabetes incidence, insulin secretion and sensitivity, oxidative stress, and endothelial function during 108 months among subjects at high risk of developing type 2 diabetes.

Methods

One hundred and forty-four middle-aged subjects with impaired glucose tolerance and metabolic syndrome were randomized in 2006 to an l-arginine supplementation (6.4 g orally/day) or placebo therapy lasting 18 months. This period was followed by a 90-month follow-up. The primary outcome was a diagnosis of diabetes during the 108 month study period. Secondary outcomes included changes in insulin secretion (proinsulin/c-peptide ratio), insulin sensitivity (IGI/HOMA-IR), oxidative stress (AOPPs), and vascular function. After the 18 month participation, subjects that were still free of diabetes and willing to continue their participation (104 subjects) were further followed until diabetes diagnosis, with a time span of about 9 years from baseline.

Results

Although results derived from the 18 month of the intervention study demonstrated no differences in the probability of becoming diabetics, at the end of the study, the cumulative incidence of diabetes was of 40.6% in the l-arginine group and of 57.4% in the placebo group. The adjusted HR for diabetes (l-arginine vs. placebo) was 0.66; 95% CI 0.48, 0.91; p < 0.02). Proinsulin/c-peptide ratio (p < 0.001), IGI/HOMA-IR (p < 0.01), and AOPP (p < 0.05) levels were ameliorated in l-arginine compared to placebo.

Conclusions

These results may suggest that the administration of l-arginine could delay the development of T2DM for a long period. This effect could be mediated, in some extent, by l-arginine-induced reduction in oxidative stress.

Increase in acid sphingomyelinase level in human retinal endothelial cells and CD34+ circulating angiogenic cells isolated from diabetic individuals is associated with dysfunctional retinal vasculature and vascular repair process in diabetes

BACKGROUND

Diabetic retinopathy is a microvascular disease that results from retinal vascular degeneration and defective repair due to diabetes-induced endothelial progenitor dysfunction.

OBJECTIVE

Understanding key molecular factors involved in vascular degeneration and repair is paramount for developing effective diabetic retinopathy treatment strategies. We propose that diabetes-induced activation of acid sphingomyelinase (ASM) plays essential role in retinal endothelial and CD34+ circulating angiogenic cell (CAC) dysfunction in diabetes.

METHODS

Human retinal endothelial cells (HRECs) isolated from control and diabetic donor tissue and human CD34+ CACs from control and diabetic patients were used in this study. ASM messenger RNA and protein expression were assessed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. To evaluate the effect of diabetes-induced ASM on HRECs and CD34+ CACs function, tube formation, CAC incorporation into endothelial tubes, and diurnal release of CD34+ CACs in diabetic individuals were determined.

RESULTS

ASM expression level was significantly increased in HRECs isolated from diabetic compared with control donor tissue, as well as CD34+ CACs and plasma of diabetic patients. A significant decrease in tube area was observed in HRECs from diabetic donors compared with control HRECs. The tube formation deficiency was associated with increased expression of ASM in diabetic HRECs. Moreover, diabetic CD34+ CACs with high ASM showed defective incorporation into endothelial tubes. Diurnal release of CD34+ CACs was disrupted with the rhythmicity lost in diabetic patients.

CONCLUSION

Collectively, these findings support that diabetes-induced ASM upregulation has a marked detrimental effect on both retinal endothelial cells and CACs.

The acute impact of high-dose lipid-lowering treatment on endothelial progenitor cells in patients with coronary artery disease-The REMEDY-EPC early substudy

RATIONALE AND OBJECTIVE

Endothelial progenitor cells (EPCs) play a role in vascular repair, while circulating endothelial cells (CECs) are biomarkers of vascular damage and regeneration. Statins may promote EPC/CEC mobilization in the peripheral blood. We evaluated whether pre-procedural exposure to different lipid-lowering drugs (statins±ezetimibe) can acutely increase levels/activity of EPCs/CECs in patients with stable coronary artery disease (CAD).

METHODS

In a planned sub-analysis of the Rosuvastatin For REduction Of Myocardial DamagE During Coronary AngioplastY (REMEDY) trial, 38 patients with stable CAD on chronic low-dose statin therapy were randomized, in a double-blind, placebo-controlled design, into 4 groups before PCI: i. placebo (n = 11); ii. atorvastatin (80 mg+40 mg, n = 9); iii. rosuvastatin (40 mg twice, n = 9); and iv. rosuvastatin (5 mg) and ezetimibe (10 mg) twice, (n = 9). At baseline and 24 h after treatment-before PCI-, patients underwent blinded analyses of EPCs [colony forming units-endothelial cells (CFU-ECs), endothelial colony-forming cells (ECFCs) and tubulization activity] and CECs in peripheral blood.

RESULTS

We found no significant treatment effects on parameters investigated such as number of CECs [Median (IQR): i. 0(0), ii. 4.5(27), iii. 1.9(2.3), iv. 1.9(2.3)], CFU-ECs [Median (IQR): i. 27(11), ii. 19(31), iii. 47(36), iv. 30(98)], and ECFCs [Median (IQR): i. 86(84), ii. 7(84), iii. 8/(42.5), iv. 5(2)], as well as tubulization activity [total tubuli (well), Median (IQR): i. 19(7), ii. 5(4), iii. 25(13), iv. 15(24)].

CONCLUSIONS

In this study, we found no evidence of acute changes in levels or activity of EPCs and CECs after high-dose lipid-lowering therapy in stable CAD patients.

Cell therapy of critical limb ischemia in diabetic patients - State of art

In this review we report on the state of cell therapy of critical limb ischemia (CLI) with respect to differences between diabetic and non-diabetic patients mainly from the clinical point of view. CLI is the most severe form of peripheral arterial disease and its diagnosis and treatment in diabetic patients is very difficult. The therapeutic effect of standard methods of CLI treatment is only partial - more than one third of diabetic patients are not eligible for standard revascularization; therefore, new therapeutic techniques such as cell therapy have been studied in clinical trials. Presence of CLI in patients with diabetic foot disease is associated with worse clinical outcomes such as lack of healing of foot ulcers, major amputations and premature mortality. A revascularization procedure cannot be successful as the only method in contrast to patients without diabetes, but it must always be part of a complex therapy focused not only on ischemia, but also on treatment of infection, off-loading, metabolic control of diabetes and nutrition, local therapy, etc. Therefore, the main criteria for cell therapy may vary in diabetic patients and non-diabetic persons and results of this treatment method should always be assessed in the context of ensuring comprehensive therapy. This review carries out an analysis of the source of precursor cells, route of administration and brings a brief report of published data with respect to diabetic and non-diabetic patients and our experience with autologous cell therapy of diabetic patients with CLI. Analysis of the studies in terms of diabetes is difficult, because in most of them sub-analysis for diabetic patients is not performed separately. The other problem is that it is not clear if diabetic patients received adequate complex treatment for their foot ulcers which can strongly affect the rate of major amputation as an outcome of CLI treatment.

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.

Exercise-induced endothelial progenitor cell mobilization is attenuated in impaired glucose tolerance and type 2 diabetes

Circulating endothelial progenitor cells (EPCs) contribute to vascular homeostasis and are fewer in those with type 2 diabetes mellitus (T2DM) compared with normal glucose tolerance (NGT), suggesting a link between EPCs and T2DM-associated vasculopathies. The purpose of this study was to assess EPC number and mobilization by acute submaximal exercise in older adults with NGT, impaired glucose tolerance (IGT) or T2DM. We tested the hypothesis that EPC mobilization is lower in IGT compared with NGT and further reduced in older adults with T2DM. Forty-five older (50-75 yr of age) men and women with NGT (n = 18), IGT (n = 10), or T2DM (n = 17) were characterized and underwent submaximal aerobic exercise tests with blood sampling for enumeration of vascular endothelial growth factor receptor 2+ (VEGFR2+) cells, CD34+ hematopoetic progenitor cells, and CD34+/VEGFR2+ EPCs by flow cytometry before and after exercise. Basal EPC number was 65 and 61% lower in the IGT and T2DM groups, respectively, compared with the NGT group (P < 0.05). EPC number increased 23% after acute exercise in the NGT group (P < 0.01), but did not change in the IGT or T2DM groups. Before and after exercise, VEGFR2+ cell number was lower in a stepwise manner across the NGT, IGT, and T2DM groups (P < 0.05). Basal CD34+ cell number was lower in the IGT group compared with NGT (P < 0.05), but did not change after exercise in any group. These findings suggest a CD34+/VEGFR2+ EPC mobilization defect in IGT and T2DM that could play a role in the cardiovascular diseases and capillary rarefaction associated with insulin resistance.

Glucose and acute exercise influence factors secreted by circulating angiogenic cells in vitro

Circulating angiogenic cells (CAC) influence vascular repair through the secretion of proangiogenic factors and cytokines. While CAC are deficient in patients with diabetes and exercise has a beneficial effect on CACs, the impact of these factors on paracrine secretion from CAC is unknown. We aimed to determine whether the in vitro secretion of selected cytokines and nitric oxide (NO) from CAC is influenced by hyperglycemia and acute exercise. Colony‐forming unit CAC (CFU‐CAC) were cultured from young active men (n = 9, 24 ± 2 years) at rest and after exercise under normal (5 mmol/L) and elevated (15 mmol/L) glucose. Preliminary relative multiplex cytokine analysis revealed that CAC conditioned culture media contained three of six measured cytokines: transforming growth factor‐beta‐1 (TGFβ1), tumor necrosis factor alpha (TNFα), and monocyte chemotactic protein‐1 (MCP‐1). Single quantitative cytokine analysis was used to determine the concentration of each cytokine from the four conditions. NO was measured via Griess assay. There was a significant effect of CAC exposure to in vivo exercise on in vitro TGFβ1 secretion (P = 0.024) that was independent of glucose concentration. There was no effect of glucose or acute exercise on TNFα or MCP‐1 concentration (both P > 0.05). The concentration of NO from CFU‐CAC cultured in elevated glucose was lower following acute exercise (P = 0.002) suggesting that exercise did not maintain NO secretion under hyperglycemic conditions. Our results identify paracrine signaling factors that may be responsible for the proangiogenic function of CFU‐CAC and an influence of acute exercise and elevated glucose on CFU‐CAC soluble factor secretion.

Integrating medical and surgical therapies to optimize the outcomes of type 2 diabetes

Modern treatment of type 2 diabetes must rely on therapy individualization. Morbid obesity confers an independent excess of risk to diabetes. In these individuals metabolic surgery is an opportunity the physician should consider, especially at the time of the diabetes diagnosis, because of its efficacy and long-term effects. In addition to the possible remission of diabetes, bariatric surgery is also associated with reduced risk of micro- and macrovascular complications. A multidisciplinary team approach is necessary to maximize the beneficial effects and minimize the adverse events of metabolic surgery and to ensure proper follow-up based on the residual possibility of developing complications. In this regard, a consensus on definition of remission must be reached to define the residual risk after antidiabetic drug withdrawal. Finally, randomized clinical trials are deemed necessary to establish the risk-to-benefit profile of glucose-lowering agents for those patients who have remained diabetic or experience a disease relapse.

Peripheral blood stem cell mobilization failure

Autologous hematopoietic stem cell transplantation (HSCT) is an important and often life saving treatment for many hematological malignancies and selected solid tumors. To rescue hematopoiesis after high-dose chemotherapy in autologous HSCT depends on maintaining sufficient stem cells. Hematopoietic stem cells and progenitor cells expressing CD34 in the BM are mobilized into the circulation with granulocyte-colony stimulating factor ± chemotherapy prior to autologous HSCT. One of the most important factors for success of autologous HSCT is hematopoietic stem cell (HSC) count. Minimum threshold for the engraftment of hematopoietic cells is accepted as 2 × 10(6) CD34 + cells/kg especially for platelet engraftment. Below this level it is defined as stem cell mobilization failure. There are several factors affecting stem cell mobilization: prior chemotherapy (such as fludarabine, melphalan, lenalidomide) and radiotherapy, age, type of disease, bone marrow cellularity. We tried to summarize the reasons of peripheral stem cell mobilization failure.

Hematopoietic Progenitor Cell Harvesting Is Feasible after Treatment with Brentuximab Vedotin in CD30(+) Lymphoma Patients Who Received Multiple Prior Lines of Treatment

Brentuximab vedotin (BV), an antibody-drug conjugate that targets CD30, induces high response rates in CD30(+) lymphoid malignancies. It is unknown if BV use affects procurement of autologous CD34(+) stem cells and hematopoietic engraftment after autologous stem cell transplantation (ASCT). We examined 42 patients treated with BV before mobilization. Median times from diagnosis to transplantation, from initial BV treatment to transplantation, and from last BV treatment to stem cell collection were 21 months (range, 10 to 210), 5 months (range, 1.5 to 16.8), and 30 days (range, 2 to 280), respectively. Mobilization was successful on the first attempt in 38 patients (90.4%). The median number of infused CD34(+) cells was 5.46 × 10(6)/kg (range, 1.65 to 54.78 × 10(6)/kg). The median times to neutrophil and platelet engraftment were 10 (range, 9 to 13), and 10.5 days (range, 7 to 35), respectively. BV before high-dose chemotherapy-ASCT did not adversely affect peripheral blood stem cell mobilization and subsequent engraftment in a cohort of heavily pretreated patients with CD30(+) lymphomas.

Contemporary treatment strategies for Type 2 diabetes-related macrovascular disease

Type 2 diabetes mellitus poses a major challenge to healthcare providers in the coming years as its prevalence increases across the globe. The disease doubles the risk of cardiovascular morbidity and mortality, with 70% of sufferers dying from a cardiac cause. Large clinical trials of current glucose-lowering therapies for Type 2 diabetes have shown no benefit in reducing the risk of macrovascular events. Blood pressure control, angiotensin-converting enzyme inhibitor therapy and improvement of dyslipidemia with statins have proven benefit in reducing cardiovascular risk in Type 2 diabetes. A growing understanding of the importance of pathological processes including endothelial dysfunction, abnormal growth factor biology, oxidative stress, dysregulation of adipokines and deficient vascular repair and regeneration in insulin-resistant states promises new treatments to combat the problem.

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.

Reduced levels of circulating endothelial progenitor cells in acute myocardial infarction patients with diabetes or pre-diabetes: accompanying the glycemic continuum

Background

Diabetic patients have a significantly worse prognosis after an acute myocardial infarction (AMI) than their counterparts. Previous studies have shown that the number of circulating endothelial progenitor cells (EPCs) significantly increase early after an AMI in normoglycemic patients. However, it is well known that type 2 diabetes mellitus (DM) is associated with impaired function and reduced circulating EPCs levels. Nonetheless, few studies have analyzed EPCs response of diabetics to an AMI and the EPC response of pre-diabetic patients has not been reported yet. Therefore, we hypothesized that in the acute phase of an AMI, diabetic and pre-diabetics have lower circulating EPCs levels than patients with normal glucose metabolism. We also evaluated the possible capacity of chronic antidiabetic treatment in the recovery of EPCs response to an AMI in diabetics.

Methods

One-hundred AMI patients were prospectively enrolled in the study. Using the high-performance flow cytometer FACSCanto II, circulating EPCs (CD45dimCD34+KDR+ and CD45dimCD133+KDR+ cells) were quantified, within the first 24 hours of admission. In addition, as an indirect functional parameter, we also analyzed the fraction of EPCs coexpressing the homing marker CXCR4.

Results

We found that in the acute phase of an AMI, diabetic patients presented significantly lower levels of circulating CD45dimCD34+KDR+ and CD45dimCD133+KDR+ EPCs by comparison with nondiabetics, with a parallel decrease in the subpopulations CXCR4+ (p < 0.001). Indeed, this study suggests that the impaired response of EPCs to an AMI is an early event in the natural history of DM, being present even in pre-diabetes. Our results, also demonstrated that numbers of all EPCs populations were inversely correlated with HbA1c (r = -0.432, p < 0.001 for CD45dimCD34+KDR+ cells). Finally, this study suggests that previous chronic insulin therapy (but not oral antidiabetic drugs) attenuate the deficient response of diabetic EPCs to an AMI.

Conclusion

This study indicates that there is a progressive decrease in EPCs levels, from pre-diabetes to DM, in AMI patients. Moreover, glycemic control seems to be determinant for circulating EPCs levels presented in the acute phase of an AMI and chronic insulin therapy may probably attenuate the deficit in EPCs pool seen in diabetics.

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.

Endothelial progenitor cells as a cardiometabolic risk factor marker in prediabetes

OBJECTIVE

Endothelial progenitor cells (EPCs) have recently been considered as a potential novel marker of vascular integrity, atherosclerosis and cardiovascular risk. This study was performed to investigate the main determinants of EPC levels in individuals with prediabetes.

DESIGN

Thirty-nine participants with newly diagnosed prediabetes were enrolled. Flow cytometric analysis was used to quantify EPCs (CD34+CD133+VEGFR-2+). Traditional risk factors, high-sensitivity C-reactive protein (hs-CRP), homeostasis model assessment of insulin resistance (HOMA-IR) and anthropometric parameters, including ultrasonographic-determined visceral and subcutaneous fat, were recorded.

RESULTS

In univariate analysis, EPC levels significantly correlated with waist circumference (p=0.017), mean arterial pressure (p=0.009), total cholesterol (p=0.003), hs-CRP (p=0.006), HOMA-IR (p=0.031) and visceral fat (p=0.040). However, in stepwise multivariate ordinal logistic regression analysis, only visceral fat retained its statistical significance (OR=0.79, 95%Cl:0.64-0.98, p=0.032).

CONCLUSIONS

Visceral fat seems to be the main determinant of EPC levels in individuals with prediabetes and to form a plausible link between mild metabolic abnormalities, cardiovascular risk and vascular homeostasis process.

Advances in stem cell mobilization

Use of granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood hematopoietic progenitor cells (HPCs) has largely replaced bone marrow (BM) as a source of stem cells for both autologous and allogeneic cell transplantation. With G-CSF alone, up to 35% of patients are unable to mobilize sufficient numbers of CD34 cells/kg to ensure successful and consistent multi-lineage engraftment and sustained hematopoietic recovery. To this end, research is ongoing to identify new agents or combinations which will lead to the most effective and efficient stem cell mobilization strategies, especially in those patients who are at risk for mobilization failure. We describe both established agents and novel strategies at various stages of development. The latter include but are not limited to drugs that target the SDF-1/CXCR4 axis, S1P agonists, VCAM/VLA-4 inhibitors, parathyroid hormone, proteosome inhibitors, Groβ, and agents that stabilize HIF. While none of the novel agents have yet gained an established role in HPC mobilization in clinical practice, many early studies exploring these new pathways show promising results and warrant further investigation.

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.

Caloric restriction and aging stem cells: the stick and the carrot?

Adult tissue stem cells have the ability to adjust to environmental changes and affect also the proliferation of neighboring cells, with important consequences on tissue maintenance and regeneration. Stem cell renewal and proliferation is strongly regulated during aging of the organism. Caloric restriction is the most powerful anti-aging strategy conserved throughout evolution in the animal kingdom. Recent studies relate the properties of caloric restriction to its ability in reprogramming stem-like cell states and in prolonging the capacity of stem cells to self-renew, proliferate, differentiate, and replace cells in several adult tissues. However this general paradigm presents with exceptions. The scope of this review is to highlight how caloric restriction impacts on diverse stem cell compartments and, by doing so, might differentially delay aging in the tissues of lower and higher organisms.

Depletion of circulating progenitor cells precedes overt diabetes: a substudy from the VA enhanced fitness trial

BACKGROUND

One theory of aging and disease development is that chronic injury (pathology) results in activation of regenerative processes and initial repair, with overt disease arising only after exhaustion of reparative capability leads to inadequate repair. While depletion of circulating progenitor cells (CPCs) has been noted in diabetes, the degree to which CPC depletion predates and is associated with propensity to develop overt disease is unclear.

METHODS

The Enhanced Fitness trial enrolled overweight/obese (body mass index >25) sedentary patients with glucose intolerance but without overt diabetes. Baseline CPCs were measured in 129 patients based on the cell surface markers CD34, CD133, and aldehyde dehydrogenase (ALDH) activity. HgbA1C, fasting insulin and glucose levels, and HOMA calculations were ascertained.

RESULTS

Lower counts of early angiogenic CPCs identified as CD34(+), CD34(+)CD133(+), and ALDH-bright (ALDH(br)) cells were associated with impairments in glucose homeostasis as reflected by HgbA1C, but not fasting insulin, glucose, or HOMA-IR. These associations remained when corrected for age and cardiovascular risk factors.

CONCLUSIONS/INTERPRETATION

The numbers of CD34(+) and ALDH(br) CPCs were significantly lower in patients with impaired glucose tolerance. Depletion of reparative capacity as reflected by loss of CPCs may presage overt disease as exemplified in this pre-diabetes model.

The effect of diabetes mellitus and end-stage renal disease on the number of CD34+ cells in the blood

The aim of this study was to investigate the effect of end-stage renal disease (ESRD) and diabetes mellitus (DM) on the number of stem cells in the peripheral blood. Sixty-two patients diagnosed with ESRD who had not received dialysis previously, 25 patients with a diagnosis of DM without nephropathy, and 21 healthy volunteers were included in the study. The group diagnosed with ESRD was divided into two groups. The first group (DM-CRD) consisted of 28 patients with DM who had developed chronic renal disease (CRD). The second group (NON-DM-CRD) consisted of 34 patients without DM who had CRD by etiology. The routine complete blood count, renal function, and number of CD34+ cells were determined for all of those involved in the study. The microalbumin/creatinine levels were measured, and glomerular filtration rates were calculated in all patients. The number of CD34+ cells was found to be significantly lower in the DM control group and DM-CRD group compared with the healthy group. No statistically significant difference was found between the NON-DM-CRD and the healthy control group. There was a moderate negative correlation between the ratio of microalbumin/creatinine and the number of CD34+ cells. A significant reduction in the number of CD34+ cells was shown in subjects with DM and ESRD caused by diabetic nephropathy.

Activated platelets correlate with mobilization of naïve CD34(+) cells and generation of CD34(+) /KDR(+) cells in the circulation. A meta-regression analysis

BACKGROUND

Bone marrow-derived circulating CD34(+) progenitor cells participate in remodeling and repair of the vasculature. Coexpression of the kinase-insert domain-containing receptor (KDR) has been proposed to identify the regenerative capacity. Recently, we provided evidence that the major fraction of circulating CD34(+) /KDR(+) cells is not mobilized from bone marrow, but is generated at sites of vascular injury through interaction with platelets.

OBJECTIVES

To determine the relationship between platelet activation, the recruitment of naïve CD34(+) cells and the generation of CD34(+) /KDR(+) progenitor cells in a broad range of (patho)physiologic conditions, a detailed meta-regression analysis was conducted.

METHODS/RESULTS

Twenty-eight conditions were found in which the numbers of CD34(+) and/or CD34(+) /KDR(+) cells and the levels of soluble P-selectin, as a marker for in vivo platelet activation, were documented. To combine heterogeneous data from 214 selected articles, results were standardized to a uniform scale by calculating standardized mean differences (SMDs) obtained from patient and control cohorts. Subsequently, a random-effects meta-regression analysis was performed on pooled SMDs.

CONCLUSIONS

Our systemic survey supports a model in which activated platelets are a determinant for mobilization of CD34(+) cells from the bone marrow and the generation of CD34(+) /KDR(+) cells in the circulation.

Human endothelial progenitor cells

Human endothelial progenitor cells (EPCs) have been generally defined as circulating cells that express a variety of cell surface markers similar to those expressed by vascular endothelial cells, adhere to endothelium at sites of hypoxia/ischemia, and participate in new vessel formation. Although no specific marker for an EPC has been identified, a panel of markers has been consistently used as a surrogate marker for cells displaying the vascular regenerative properties of the putative EPC. However, it is now clear that a host of hematopoietic and vascular endothelial subsets display the same panel of antigens and can only be discriminated by an extensive gene expression analysis or use of a variety of functional assays that are not often applied. This article reviews our current understanding of the many cell subsets that constitute the term EPC and provides a concluding perspective as to the various roles played by these circulating or resident cells in vessel repair and regeneration in human subjects.

Importance of insulin resistance to vascular repair and regeneration

Metabolic insulin resistance is apparent across a spectrum of clinical disorders, including obesity and diabetes, and is characterized by an adverse clustering of cardiovascular risk factors related to abnormal cellular responses to insulin. These disorders are becoming increasingly prevalent and represent a major global public health concern because of their association with significant increases in atherosclerosis-related mortality. Endogenous repair mechanisms are thought to retard the development of vascular disease, and a growing evidence base supports the adverse impact of the insulin-resistant phenotype upon indices of vascular repair. Beyond the impact of systemic metabolic changes, emerging data from murine studies also provide support for abnormal insulin signaling at the level of vascular cells in retarding vascular repair. Interrelated pathophysiological factors, including reduced nitric oxide bioavailability, oxidative stress, altered growth factor activity, and abnormal intracellular signaling, are likely to act in conjunction to impede vascular repair while also driving vascular damage. Understanding of these processes is shaping novel therapeutic paradigms that aim to promote vascular repair and regeneration, either by recruiting endogenous mechanisms or by the administration of cell-based therapies.

Low clonogenic potential of circulating angiogenic cells is associated with lower density of capillaries in skeletal muscle in patients with impaired glucose tolerance

BACKGROUND

Reduced density of capillaries in skeletal muscle can limit insulin, glucose, and oxygen supply to the muscle, thereby contributing to worsening metabolism in older adults. The lower skeletal muscle capillarization in impaired glucose tolerance (IGT) may partially be due to circulating angiogenic cell dysfunction. Circulating angiogenic cells maintain the vasculature and promote angiogenesis, but circulating angiogenic cell number and function may be reduced in IGT. The goal of this study was to determine whether the clonogenic potential of circulating angiogenic cells is lower in IGT compared with normal-glucose-tolerant (NGT) controls and is associated with skeletal muscle capillarization.

METHODS

Glucose tolerance, endothelial cell colony-forming unit (CFU-EC) number, and vastus lateralis capillary density were measured in sedentary, older (62 ± 1 years, mean ± SEM) men and women with NGT (n = 16) and IGT (n = 12).

RESULTS

Adults with IGT had 43% lower CFU-EC number (11.4 ± 2.3 versus 20.1 ± 2.0 colonies, p < 0.01) and 12% lower capillary density (291 ± 11 versus 330 ± 9 capillaries/mm², p < 0.01) compared with those with NGT. In regression analyses, CFU-EC number inversely correlated with 120-min postprandial glucose in all subjects (r = -0.47, p < 0.05), and capillary density was directly associated with CFU-EC number (r = 0.53, p < 0.05).

CONCLUSIONS

We conclude that the clonogenic potential of circulating angiogenic cells is lower in sedentary older adults with IGT and is associated with lower skeletal muscle capillarization. Low circulating angiogenic cell clonogenic potential in IGT suggests a state of impaired angiogenesis occurring prior to overt type 2 diabetes that may mediate early microvascular changes in the development and progression of IGT to type 2 diabetes.

Endothelial progenitor cells, cardiovascular risk factors and lifestyle modifications

Endothelial progenitor cells (EPCs) contribute substantially to preservation of a structurally and functionally intact endothelium. EPCs home in to the sites of endothelial injury and ischemia, where they proliferate, differentiate and integrate into the endothelial layer or exert a paracrine function by producing vascular growth factors. This review will focus on successful lifestyle interventions that aim to maintain vascular health through beneficial actions on cell populations with vasculogenic potential. The results of the studies proving the role of healthy lifestyle are particularly emphasized.

Impact of ADMA, endothelial progenitor cells and traditional cardiovascular risk factors on pulse wave velocity among prediabetic individuals

Background

Central arterial stiffness represents a well-established predictor of cardiovascular disease. Decreased circulating endothelial progenitor cells (EPCs), increased asymmetric dimethyl-arginine (ADMA) levels, traditional cardiovascular risk factors and insulin resistance have all been associated with increased arterial stiffness. The correlations of novel and traditional cardiovascular risk factors with central arterial stiffness in prediabetic individuals were investigated in the present study.

Methods

The study population consisted of 53 prediabetic individuals. Individuals were divided into groups of isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT) and combined IGT-IFG. Age, sex, family history of diabetes, smoking history, body mass index (BMI), waist to hip ratio (WHR), waist circumference (WC), blood pressure, lipid profile, levels of high sensitive C-reactive protein (hsCRP), glomerular filtration rate (GFR), and history of antihypertensive or statin therapy were obtained from all participants. Insulin resistance was evaluated using the Homeostatic Model Assessment (HOMA-IR). Carotid -femoral pulse wave velocity was used as an index of arterial stiffness. Circulating EPC count and ADMA serum levels were also determined.

Results

Among studied individuals 30 (56.6%) subjects were diagnosed with isolated IFG, 9 (17%) with isolated IGT (17%) and 14 with combined IFG-IGT (26.4%). In univariate analysis age, mean blood pressure, fasting glucose, total cholesterol, LDL cholesterol, and ADMA levels positively correlated with pulse-wave velocity while exercise and GFR correlated negatively. EPC count did not correlate with PWV. In multivariate stepwise regression analysis PWV correlated independently and positively with LDL-Cholesterol (low density lipoprotein) and ADMA levels and negatively with exercise.

Conclusions

Elevated ADMA and LDL-C levels are strongly associated with increased arterial stiffness among pre-diabetic subjects. In contrast exercise inversely correlated with arterial stiffness.

Pioglitazone improves in vitro viability and function of endothelial progenitor cells from individuals with impaired glucose tolerance

Background

Evidence suggests that the PPARγ-agonist insulin sensitizer pioglitazone, may provide potential beneficial cardiovascular (CV) effects beyond its anti-hyperglycaemic function. A reduced endothelial progenitor cell (EPC) number is associated with impaired glucose tolerance (IGT) or diabetes, conditions characterised by increased CV risk.

Aim

To evaluate whether pioglitazone can provide benefit in vitro in EPCs obtained from IGT subjects.

Materials and Methods

Early and late-outgrowth EPCs were obtained from peripheral blood mononuclear cells of 14 IGT subjects. The in vitro effect of pioglitazone (10 µM) with/without PPARγ-antagonist GW9662 (1 µM) was assessed on EPC viability, apoptosis, ability to form tubular-like structures and pro-inflammatory molecule expression.

Results

Pioglitazone increased early and late-outgrowth EPC viability, with negligible effects on apoptosis. The capacity of EPCs to form tubular-like structures was improved by pioglitazone in early (mean increase 28%; p = 0.005) and late-outgrowth (mean increase 30%; p = 0.037) EPCs. Pioglitazone reduced ICAM-1 and VCAM-1 adhesion molecule expression in both early (p = 0.001 and p = 0.012 respectively) and late-outgrowth (p = 0.047 and p = 0.048, respectively) EPCs. Similarly, pioglitazone reduced TNFα gene and protein expression in both early (p = 0.034;p = 0.022) and late-outgrowth (p = 0.026;p = 0.017) EPCs compared to control. These effects were prevented by incubation with the PPARγ-antagonist GW9662.

Conclusion

Pioglitazone exerts beneficial effects in vitro on EPCs isolated from IGT subjects, supporting the potential implication of pioglitazone as a CV protective agents.

Advances in stem cell mobilization

The use of mobilized peripheral blood stem cells (PBSCs) has largely replaced the use of bone marrow as a source of stem cells for both allogeneic and autologous stem cell transplantation. G-CSF with or without chemotherapy is the most commonly used regimen for stem cell mobilization. Some donors or patients, especially the heavily pretreated patients, fail to mobilize the targeted number of stem cells with this regimen. A better understanding of the mechanisms involved in hematopoietic stem cell (HSC) trafficking could lead to the development of newer mobilizing agents and therapeutic approaches. This review will cover the current methods for stem cell mobilization and recent developments in the understanding of the biology of stem cells and the bone marrow microenvironment.

Impact of serum source and inflammatory cytokines on the isolation of endothelial colony-forming cells from peripheral blood

Endothelial colony-forming cells (ECFCs) isolated from peripheral blood are a highly promising cell source for a wide range of applications, including tissue engineering, in vivo vasculogenesis and anti-cancer therapeutics. Because of the potential for clinical translation, it is increasingly important to isolate and study ECFCs from patient cohorts that may benefit from such technologies. The primary objective of this investigation was to determine whether ECFCs could be obtained from patients with chronic kidney disease and diabetes (CKD-DM), using techniques that can be readily applied in the clinical setting. We also investigated the impact of autologous vs commercially available (i.e. allogeneic) human serum on ECFCs isolation. Surprisingly, the efficacy of ECFCs isolation from the CKD-DM group was comparable to a healthy control group when autologous serum was used. In contrast, substitution of allogeneic serum reduced ECFCs isolation in CKD-DM and control groups. In characterization studies, ECFCs were positive for several endothelial cell markers. ECFCs from the CKD-DM group were sensitive to inflammatory activation but their cellular proliferation was compromised. The concentrations of IL-4 and IL-8 were significantly increased in allogeneic serum, which induced a pro-inflammatory environment, including the release of IL-4, IL-6, IL-8 and MCP-1 into the conditioned media of cell cultures. Taken together, these data support further investigation into the use of autologous serum and cells for ECFC-based therapeutics and underscore the importance of the cytokine content in serum used for ECFCs isolation.

Critical reevaluation of endothelial progenitor cell phenotypes for therapeutic and diagnostic use

Diverse subsets of endothelial progenitor cells (EPCs) are used for the treatment of ischemic diseases in clinical trials, and circulating EPCs levels are considered as biomarkers for coronary and peripheral artery disease. However, despite significant steps forward in defining their potential for both therapeutic and diagnostic purposes, further progress has been mired by unresolved questions around the definition and the mechanism of action of EPCs. Diverse culturing methods and detection of various combinations of different surface antigens were used to enrich and identify EPCs. These attempts were particularly challenged by the close relationship and overlapping markers of the endothelial and hematopoietic lineages. This article will critically review the most commonly used protocols to define EPCs by culture assays or by fluorescence-activated cell sorter in the context of their therapeutic or diagnostic use. We also delineate new research avenues to move forward our knowledge on EPC biology.