Endothelial progenitor cells and cardiovascular homeostasis: Clinical implications

Responses of Endothelial Progenitor Cells to Chronic and Acute Physical Activity in Healthy Individuals

Endothelial progenitor cells (EPCs) are circulating cells of various origins that possess the capacity for renewing and regenerating the endothelial lining of blood vessels. During physical activity, in response to factors such as hypoxia, changes in osmotic pressure, and mechanical forces, endothelial cells undergo intense physiological stress that results in endothelial damage. Circulating EPCs participate in blood vessel repair and vascular healing mainly through paracrine signalling. Furthermore, physical activity may play an important role in mobilising this important cell population. In this narrative review, we summarise the current knowledge on the biology of EPCs, including their characteristics, assessment, and mobilisation in response to both chronic and acute physical activity in healthy individuals.

Could endothelial progenitor cells complement the diagnosis of inflammatory arthritis? A systematic review and meta-analysis

The objective of this meta-analysis was to systematically review existing evidence and evaluate variations in levels of circulating endothelial progenitor cells (EPCs) among individuals with psoriatic arthritis (PsA), juvenile idiopathic arthritis (JIA), and rheumatoid arthritis (RA). Relevant studies were identified through database searches, and 20 records were enrolled. We used the fixed-effect model or random-effect model to estimate the pooled standardized mean difference (SMD) with 95% confidence intervals (CIs) in circulating EPC levels between inflammatory arthritis patients and controls. The results showed that circulating EPC levels differed among subtypes of inflammatory arthritis, with significantly lower levels in patients with RA (SMD = -0.848, 95% CI = -1.474 to -0.221, p = 0.008) and PsA (SMD = -0.791, 95% CI = -1.136 to -0.446, p < 0.001). However, no statistically significant difference was found in circulating EPC levels between patients with JIA and controls (SMD = -1.160, 95% CI = -2.578 to 0.259, p = 0.109). Subgroup analyses suggested that in patients with RA, circulating EPC levels were influenced by age, disease activity, and duration. Although many studies have investigated circulating EPC levels in patients with inflammatory arthritis, the results have been inconsistent. This meta-analysis offers a comprehensive overview of the existing evidence and emphasizes the association between levels of circulating EPCs and various types of arthritis. However, further research is needed to determine the specific mechanisms underlying the observed differences in EPC levels in different types of arthritis and to establish the clinical utility of this biomarker.

Endothelial senescence in vascular diseases: current understanding and future opportunities in senotherapeutics

Senescence compromises the essential role that the endothelium plays in maintaining vascular homeostasis, so promoting endothelial dysfunction and the development of age-related vascular diseases. Their biological and clinical significance calls for strategies for identifying and therapeutically targeting senescent endothelial cells. While senescence and endothelial dysfunction have been studied extensively, distinguishing what is distinctly endothelial senescence remains a barrier to overcome for an effective approach to addressing it. Here, we review the mechanisms underlying endothelial senescence and the evidence for its clinical importance. Furthermore, we discuss the current state and the limitations in the approaches for the detection and therapeutic intervention of target cells, suggesting potential directions for future research.

Liraglutide Improves the Angiogenic Capability of EPC and Promotes Ischemic Angiogenesis in Mice under Diabetic Conditions through an Nrf2-Dependent Mechanism

The impairment in endothelial progenitor cell (EPC) functions results in dysregulation of vascular homeostasis and dysfunction of the endothelium under diabetic conditions. Improving EPC function has been considered as a promising strategy for ameliorating diabetic vascular complications. Liraglutide has been widely used as a therapeutic agent for diabetes. However, the effects and mechanisms of liraglutide on EPC dysfunction remain unclear. The capability of liraglutide in promoting blood perfusion and angiogenesis under diabetic conditions was evaluated in the hind limb ischemia model of diabetic mice. The effect of liraglutide on the angiogenic function of EPC was evaluated by cell scratch recovery assay, tube formation assay, and nitric oxide production. RNA sequencing was performed to assess the underlying mechanisms. Liraglutide enhanced blood perfusion and angiogenesis in the ischemic hindlimb of db/db mice and streptozotocin-induced type 1 diabetic mice. Additionally, liraglutide improved tube formation, cell migration, and nitric oxide production of high glucose (HG)-treated EPC. Assessment of liraglutide target pathways revealed a network of genes involved in antioxidant activity. Further mechanism study showed that liraglutide decreased the production of reactive oxygen species and increased the activity of nuclear factor erythroid 2-related factor 2 (Nrf2). Nrf2 deficiency attenuated the beneficial effects of liraglutide on improving EPC function and promoting ischemic angiogenesis under diabetic conditions. Moreover, liraglutide activates Nrf2 through an AKT/GSK3β/Fyn pathway, and inhibiting this pathway abolished liraglutide-induced Nrf2 activation and EPC function improvement. Overall, these results suggest that Liraglutide represents therapeutic potential in promoting EPC function and ameliorating ischemic angiogenesis under diabetic conditions, and these beneficial effects relied on Nrf2 activation.

Non-Linear Association Between Serum Alkaline Phosphatase and 3-Month Outcomes in Patients With Acute Stroke: Results From the Xi'an Stroke Registry Study of China

Background

Alkaline phosphatase (ALP) is associated with an increased risk of cardiovascular events and is closely related to adverse outcomes after stroke. However, the regional investigation into the associations of ALP with acute stroke (AS) outcomes is limited. This study aimed to identify the association between serum ALP levels and clinical outcomes 3 months after AS in the Xi'an district of China.

Methods

We enrolled all patients with AS from 4 hospitals in the Xi'an district from January to December 2015. ALP levels and related patient information were collected at admission, and the events of stroke outcomes were followed up 1 and 3 months after diagnosis. ALP levels were analyzed as continuous variables and quartiles (Q1–Q4). The outcomes included all-cause mortality, recurrent stroke, and poor functional outcomes (modified Rankin Scale score of 3–6) within 3 months. A multivariate logistic regression and interaction analyses were performed to evaluate the independent association between serum ALP level and 3-month stroke outcomes.

Results

Overall, 2,799 patients with AS were enrolled in this study. The mean age was 63.9 ± 12.5 years. In the Q4 (≥93.0 U/L) group, the incidences of all-cause mortality, recurrent stroke, and poor functional outcomes were 7.8, 2.7, and 24.9%, respectively. After being adjusted for confounding variables, patients in Q4 (≥93.0 U/L) were related to an increased risk of all-cause mortality [odds ratio (OR) = 2.17, 95% CI: 1.19–3.96; P = 0.011] and patients in Q3 (76.8–92.9 U/L) were related to a lower risk of recurrent stroke (OR = 0.37, 95% CI: 0.14–0.97; P = 0.043) at the 3-month time point, compared to those in Q2 (63.0–76.7 U/L). The optimal range of ALP for all-cause mortality was seen in Q2, with a nadir level of 70 U/L. However, differences were statistically insignificant between ALP levels and poor functional outcomes (P > 0.05). Moreover, there was no significant interaction between ALP levels and age, gender, drinking status, smoking status, or pneumonia (P > 0.05) for all outcomes.

Conclusion

Non-linear associations were observed between serum ALP levels and 3-month outcomes in patients with AS. It might be beneficial to reduce the risk of all-cause mortality and recurrent stroke by maintaining ALP at optimal ranges.

Protective effects of endothelial progenitor cell microvesicles on Ang II‑induced rat kidney cell injury

Chronic hypertension can lead to kidney damage, known as hypertensive nephropathy or hypertensive nephrosclerosis. Further understanding of the molecular mechanisms via which hypertensive nephropathy develops is essential for effective diagnosis and treatment. The present study investigated the mechanisms by which endothelial progenitor cells (EPCs) repair primary rat kidney cells (PRKs). ELISA, Cell Counting Kit-8 and flow cytometry assays were used to analyze the effects of EPCs or EPC-MVs on the oxidative stress, inflammation, cell proliferation, apoptosis and cycle of PRKs induced by AngII. A PRK injury model was established using angiotensin II (Ang II). After Ang II induction, PRK proliferation was decreased, apoptosis was increased and the cell cycle was blocked at the G₁ phase before entering the S phase. It was found that the levels of reactive oxygen species and malondialdehyde were increased, while the levels of glutathione peroxidase and superoxide dismutase were decreased. Moreover, the levels of the inflammatory cytokines IL-1β, IL-6 and TNF-α were significantly increased. Thus, Ang II damaged PRKs by stimulating oxidative stress and promoting the inflammatory response. However, when PRKs were co-cultured with EPCs, the damage induced by Ang II was significantly reduced. The current study collected the microvesicles (MVs) secreted by EPCs and co-cultured them with Ang II-induced PRKs, and identified that EPC-MVs retained their protective effect on PRKs. In conclusion, EPCs protect PRKs from Ang II-induced damage via secreted MVs.

Polysaccharide peptide (PsP) Ganoderma lucidum: a potential inducer for vascular repair in type 2 diabetes mellitus model

INTRODUCTION

The increasing blood glucose level due to insulin resistance which occurs in diabetes mellitus (DM) may cause vascular damage. This study aims to prove the effect of the polysaccharide peptide (PsP) Ganoderma lucidum on improving vascular damage through an increase of circulating endothelial cells and circulating endothelial cells (CEC) ratio, decreased H2O2, triglyceride (TG), total cholesterol (TC) and insulin resistance in type 2 DM.

METHODS

Our study is a true experimental study with randomized posttest control group design that used 35 Wistar rats divided into five groups: normal, control (+) and three groups of different variant PsP doses 50, 150 and 300 mg/kg BW (n=7).

RESULTS

By using one-way ANOVA and post-hoc Duncan test, the results show a significant increase of endothelial progenitor cell (EPC) concentration (p=0.000) and ratio EPC:CEC (0.000) by dose-dependent fashion and also reduced CEC concentration (p=0.001), H2O2 (p=0.03), TG (p=0.001), TC (p=0.01) and insulin resistance (p=0.003).

CONCLUSION

In this study, PsP induced endothelial repairing process and reduced the risk factor with 300 mg/kg BW as optimum dose. However, further research on EPC and CEC detection markers is important. Further research on PsP and clinical trial for commercial uses is also needed.

Serum Level of Endothelial Cell-Specific Molecule -1 (ESM -1) as a New Potential Biomarker for Rheumatoid Arthritis Disease Activity

Background:

Rheumatoid arthritis is a chronic inflammatory autoimmune disease characterized by destruction of the joint cartilage and bone. Endothelial dysfunction (ED) in RA may be related to disease activity. Our objective is to explore serum levels of endothelial cell-specific molecule-1 (ESM-1) as a biomarker for RA disease activity.

Methods:

A cross-sectional study was carried out and included 83 adult patients with RA, in addition to 20 healthy subjects (age and sex-matched) as a control group. Based on Disease Activity Score in 28 joints (DAS-28), the patient's group was subdivided into four subgroups(remission, mild, moderate and severe disease activity state). The demographic & clinical data, BMI, DAS-28 and Serological assessment [Erythrocyte Sedimentation Rate (ESR), CRP, Rheumatoid Factor (RF) and Anti-Citrullinated Peptide Antibody (ACPA)] were recorded. ESM-1was assayed for all participants.

Results:

Serum levels of ESM1 were significantly higher in the patient group than the control group (P< 0.0001). ESM-1 serum levels were significantly higher in patients with severe disease activity subgroup compared with patients with remission and mild disease activity subgroups (P< 0.0001). ESM-1 was positively and significantly correlated with DAS-28 score, The Health Assessment Questionnaire Disability Index (HAQ-DI) and modified Larsen score (P= 0.002, 0.0001 & 0.0001 respectively).

Conclusion:

ESM-1 could be a biomarker for RA disease activity.

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

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

Endothelial progenitor cells in cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of death in both developed and developing countries. Endothelial progenitor cells (EPCs) are derived from hematopoietic stem cells with powerful function of angiogenesis. There are many studies on the relation between coronary heart disease and circulating EPCs. In this review, we discuss biological characteristics of endothelial progenitor cells, some influencing factors of the number and function of EPCs, and the role of EPCs in the treatment of cardiovascular disease. At last, we bring some perspectives on the future of endothelial progenitor cell therapy.

Regulatory effects of miR-146a/b on the function of endothelial progenitor cells in acute ischemic stroke in mice

The study aims to explore how microRNA-146a/b (miR-146a/b) regulates the function of endothelial progenitor cells (EPCs) in acute ischemic stroke in mice. Eighty male SPF C57BL/6J mice were evenly divided into the model-6 h, model-12 h, model-24 h (mice suffered from middle cerebral artery occlusion [MCAO] for 6 h, 12 h and model-24 h) and normal groups. EPCs were transfected and assigned into the control, MCAO, MCAO-miR-146a, MCAO-miR-146b and MCAO-miR-146a/b groups. The qRT-PCR was used to detect miR-146a/b expression in EPCs. Expressions of tumor necrosis factor receptor-associated factor 6 (TRAF6) and interleukin-1 receptor-associated kinase 1 (IRAK1) were detected using western blotting. Cell proliferation and migration of EPCs were testified using CCK-8 assay and scratch test, respectively. Angiogenesis ability of EPCs was observed under microscope. MiR-146a and miR-146b expressions were lower in the model groups than the normal group. There were up-regulated TRAF6 and IRAK1 expressions in the model-6 h, model-12 h and model-24 h groups compared with the normal group. And there were down-regulated TRAF6 and IRAK1 expressions in the MCAO-miR-146a, MCAO-miR-146b and MCAO-miR-146a/b groups than in the MCAO group. Compared with the control group, the proliferation, migration and angiogenesis ability of EPCs were significantly lower in the MCAO group, but higher in the MCAO-miR-146a, MCAO-miR-146b and MCAO-miR-146a/b groups. Besides, the miR-146a/b group showed more enhancement than the MCAO-miR-146a and MCAO-miR-146b groups. MiR-146a/b could down-regulate the TRAF6 and IRAK1 expressions and promote proliferation, migration and angiogenesis ability of EPCs, which was important for recovery of patients with hyperacute ischemic stroke.

GMP-conformant on-site manufacturing of a CD133+ stem cell product for cardiovascular regeneration

Background

CD133⁺ stem cells represent a promising subpopulation for innovative cell-based therapies in cardiovascular regeneration. Several clinical trials have shown remarkable beneficial effects following their intramyocardial transplantation. Yet, the purification of CD133⁺ stem cells is typically performed in centralized clean room facilities using semi-automatic manufacturing processes based on magnetic cell sorting (MACS®). However, this requires time-consuming and cost-intensive logistics.

Methods

CD133⁺ stem cells were purified from patient-derived sternal bone marrow using the recently developed automatic CliniMACS Prodigy® BM-133 System (Prodigy). The entire manufacturing process, as well as the subsequent quality control of the final cell product (CP), were realized on-site and in compliance with EU guidelines for Good Manufacturing Practice. The biological activity of automatically isolated CD133⁺ cells was evaluated and compared to manually isolated CD133⁺ cells via functional assays as well as immunofluorescence microscopy. In addition, the regenerative potential of purified stem cells was assessed 3 weeks after transplantation in immunodeficient mice which had been subjected to experimental myocardial infarction.

Results

We established for the first time an on-site manufacturing procedure for stem CPs intended for the treatment of ischemic heart diseases using an automatized system. On average, 0.88 × 10⁶ viable CD133⁺ cells with a mean log₁₀ depletion of 3.23 ± 0.19 of non-target cells were isolated. Furthermore, we demonstrated that these automatically isolated cells bear proliferation and differentiation capacities comparable to manually isolated cells in vitro. Moreover, the automatically generated CP shows equal cardiac regeneration potential in vivo.

Conclusions

Our results indicate that the Prodigy is a powerful system for automatic manufacturing of a CD133⁺ CP within few hours. Compared to conventional manufacturing processes, future clinical application of this system offers multiple benefits including stable CP quality and on-site purification under reduced clean room requirements. This will allow saving of time, reduced logistics and diminished costs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0467-0) contains supplementary material, which is available to authorized users.

Prominin-1/CD133 expression as potential tissue-resident vascular endothelial progenitor cells in the pulmonary circulation

Pulmonary vascular endothelial cells could contribute to maintain homeostasis in adult lung vasculature. "Tissue-resident" endothelial progenitor cells (EPCs) play pivotal roles in postnatal vasculogenesis, vascular repair, and tissue regeneration; however, their local pulmonary counterparts remain to be defined. To determine whether prominin-1/CD133 expression can be a marker of tissue-resident vascular EPCs in the pulmonary circulation, we examined the origin and characteristics of prominin-1/CD133-positive (Prom1(+)) PVECs considering cell cycle status, viability, histological distribution, and association with pulmonary vascular remodeling. Prom1(+) PVECs exhibited high steady-state transit through the cell cycle compared with Prom1(-) PVECs and exhibited homeostatic cell division as assessed using the label dilution method and mice expressing green fluorescent protein. In addition, Prom1(+) PVECs showed more marked expression of putative EPC markers and drug resistance genes as well as highly increased activation of aldehyde dehydrogenase compared with Prom1(-) PVECs. Bone marrow reconstitution demonstrated that tissue-resident cells were the source of >98% of Prom1(+) PVECs. Immunofluorescence analyses revealed that Prom1(+) PVECs preferentially resided in the arterial vasculature, including the resistant vessels of the lung. The number of Prom1(+) PVECs was higher in developing postnatal lungs. Sorted Prom1(+) PVECs gave rise to colonies and formed fine vascular networks compared with Prom1(-) PVECs. Moreover, Prom1(+) PVECs increased in the monocrotaline and the Su-5416 + hypoxia experimental models of pulmonary vascular remodeling. Our findings indicated that Prom1(+) PVECs exhibited the phenotype of tissue-resident EPCs. The unique biological characteristics of Prom1(+) PVECs predominantly contribute to neovasculogenesis and maintenance of homeostasis in pulmonary vascular tissues.

Endothelial Dysfunction and Inflammation: Immunity in Rheumatoid Arthritis

Inflammation, as a feature of rheumatoid arthritis (RA), leads to the activation of endothelial cells (ECs). Activated ECs induce atherosclerosis through an increased expression of leukocyte adhesion molecules. Endothelial dysfunction (ED) is recognized as a failure of endothelial repair mechanisms. It is also an early preclinical marker of atherosclerosis and is commonly found in RA patients. RA is now established as an independent cardiovascular risk factor, while mechanistic determinants of ED in RA are still poorly understood. An expanding body of study has shown that EC at a site of RA is both active participant and regulator of inflammatory process. Over the last decade, a role for endothelial dysfunction in RA associated with cardiovascular disease (CVD) has been hypothesized. At the same time, several maintenance drugs targeting this phenomenon have been tested, which has promising results. Assessment of endothelial function may be a useful tool to identify and monitor RA patients.

Involvement of NADPH oxidases and non-muscle myosin light chain in senescence of endothelial progenitor cells in hyperlipidemia

NADPH oxidase (NOX)-derived reactive oxygen species (ROS) is involved in endothelial dysfunction of hyperlipidemia, and non-muscle myosin regulatory light chain (nmMLC20) is reported to have a transcriptional function in regulation of gene expression. The purposes of this study are to determine whether NOX-derived ROS can promote endothelial progenitor cell (EPC) senescence and whether nmMLC20 can regulate NOX expression through a phosphorylation-dependent manner. The rats were subjected to 8 weeks of high-fat diet feeding to establish a hyperlipidemic model, which showed an increase in plasma lipids and the accelerated senescence and reduced number of circulating EPCs, accompanied by an increase in myosin light chain kinase (MLCK) and NOX activities, p-nmMLC20 level, NOX (NOX2, NOX4) expression, and H2O2 content. Next, EPCs isolated from normal rats were incubated with ox-LDL (100 μg/mL) for 24 h to establish a senescent model in vitro. Consistent with our in vivo findings, ox-LDL treatment increased the senescence of EPCs concomitant with an increase in MLCK and NOX activities, p-nmMLC20 level (in total or nuclear proteins), NOX expression, and H2O2 content; these phenomena were reversed by MLCK inhibitor. NOX inhibitor achieved similar results to that of MLCK inhibitor except that there is no effect on MLCK activity and p-nmMLC20 level. Furthermore, knockdown of nmMLC20, NOX2, or NOX4 led to a down-regulation in NOX and a reduction in ox-LDL-induced EPC senescence. These results suggest that NOX-derived ROS promotes the senescence of circulating EPCs in hyperlipidemia and nmMLC20 may play a transcriptional role in the upregulation of NOX through a phosphorylation-dependent manner.

Endothelial progenitor cells as a biological marker of peripheral artery disease

The role of endothelial progenitor cells (EPCs) in peripheral artery disease (PAD) remains unclear. We hypothesized that EPC mobilization and function play a central role in the development of endothelial dysfunction and directly influence the degree of atherosclerotic burden in peripheral artery vessels. The number of circulating EPCs, defined as CD34(+)/KDR(+) cells, were assessed by flow cytometry in 91 subjects classified according to a predefined sample size of 31 non-diabetic PAD patients, 30 diabetic PAD patients, and 30 healthy volunteers. Both PAD groups had undergone endovascular treatment in the past. As a functional parameter, EPC colony-forming units were determined ex vivo. Apart from a broad laboratory analysis, a series of clinical measures using the ankle-brachial index (ABI), flow-mediated dilatation (FMD) and carotid intima-media thickness (cIMT) were investigated. A significant reduction of EPC counts and proliferation indices in both PAD groups compared to healthy subjects were observed. Low EPC number and pathological findings in the clinical assessment were strongly correlated to the group allocation. Multivariate statistical analysis revealed these findings to be independent predictors of disease appearance. Linear regression analysis showed the ABI to be a predictor of circulating EPC number (p=0.02). Moreover, the functionality of EPCs was correlated by linear regression (p=0.017) to cIMT. The influence of diabetes mellitus on EPCs in our study has to be considered marginal in already disease-affected patients. This study demonstrated that EPCs could predict the prevalence and severity of symptomatic PAD, with ABI as the determinant of the state of EPC populations in disease-affected groups.

Full GMP-compliant validation of bone marrow-derived human CD133(+) cells as advanced therapy medicinal product for refractory ischemic cardiomyopathy

According to the European Medicine Agency (EMA) regulatory frameworks, Advanced Therapy Medicinal Products (ATMP) represent a new category of drugs in which the active ingredient consists of cells, genes, or tissues. ATMP-CD133 has been widely investigated in controlled clinical trials for cardiovascular diseases, making CD133⁺ cells one of the most well characterized cell-derived drugs in this field. To ensure high quality and safety standards for clinical use, the manufacturing process must be accomplished in certified facilities following standard operative procedures (SOPs). In the present work, we report the fully compliant GMP-grade production of ATMP-CD133 which aims to address the treatment of chronic refractory ischemic heart failure. Starting from bone marrow (BM), ATMP-CD133 manufacturing output yielded a median of 6.66 × 10⁶ of CD133⁺ cells (range 2.85 × 10⁶–30.84 × 10⁶), with a viability ranged between 96,03% and 99,97% (median 99,87%) and a median purity of CD133⁺ cells of 90,60% (range 81,40%–96,20%). Based on these results we defined our final release criteria for ATMP-CD133: purity ≥ 70%, viability ≥ 80%, cellularity between 1 and 12 × 10⁶ cells, sterile, and endotoxin-free. The abovementioned criteria are currently applied in our Phase I clinical trial (RECARDIO Trial).

SOCE and cancer: Recent progress and new perspectives

Ca²⁺ acts as a universal and versatile second messenger in the regulation of a myriad of biological processes, including cell proliferation, differentiation, migration and apoptosis. Store‐operated Ca²⁺ entry (SOCE) mediated by ORAI and the stromal interaction molecule (STIM) constitutes one of the major routes of calcium entry in nonexcitable cells, in which the depletion of intracellular Ca²⁺ stores triggers activation of the endoplasmic reticulum (ER)‐resident Ca²⁺ sensor protein STIM to gate and open the ORAI Ca²⁺ channels in the plasma membrane (PM). Accumulating evidence indicates that SOCE plays critical roles in cancer cell proliferation, metastasis and tumor neovascularization, as well as in antitumor immunity. We summarize herein the recent advances in our understanding of the function of SOCE in various types of tumor cells, vascular endothelial cells and cells of the immune system. Finally, the therapeutic potential of SOCE inhibitors in the treatment of cancer is also discussed.

Angiogenic T cells are decreased in rheumatoid arthritis patients

OBJECTIVE

The mechanisms underlying the increased cardiovascular risk (CVR) of rheumatoid arthritis (RA) patients remain unclear. Since the recently discovered angiogenic T cells (Tang) could have a role in endothelial repair through cooperating with endothelial progenitor cells (EPC), the main aim of this study was to analyse the Tang and EPC populations in relation to disease-specific features and traditional CVR factors.

METHODS

Tang (CD3(+)CD31(+)CXCR4(+)) and EPC (CD34(+)VEGFR2(+)CD133(+)) populations were quantified by flow cytometry in peripheral blood samples from 103 RA patients and 18 matched healthy controls (HC). Clinical features and traditional CVR factors were obtained from clinical records, and 28-joint Disease Activity Score was used for measuring disease activity. Interferon (IFN) α serum levels were measured by immunoassays.

RESULTS

Tang and EPC were strongly decreased in RA patients. In HC, but not in patients, both populations were positively correlated and inversely related to low density lipoprotein- and total-cholesterol levels. Sex, diabetes, dyslipidaemia, hypertension or obesity did not significantly influence Tang in patients, although detected in smokers. However, Tang were closely related to disease activity, autoantibody positivity and IFNα levels. Multiple regression analysis adjusted for traditional CVR factors confirmed that only disease activity, age at diagnosis, antinuclear antibody positivity and smoking habit could predict Tang frequency. Finally, patients who had suffered a CV event since their RA diagnosis presented higher Tang decrease and IFNα levels than those who were CV event-free.

CONCLUSIONS

Disease-specific parameters, including disease activity, autoantibody profiles and IFNα levels, are associated with Tang decrease in RA, thus probably accounting for CVR.

Effect of endogenous bone marrow derived stem cells induced by AMD-3100 on expanded ischemic flap

The purpose of this study was to devise an expanded ischemic flap model and to investigate the role of AMD-3100 (Plerixafor, chemokine receptor 4 inhibitor) in this model by confirming its effect on mobilization of stem cells from the bone marrow. Male Sprague-Dawley rats were used as an animal research model. The mobilization of stem cells from the bone marrow was confirmed in the AMD-3100-treated group. The fractions of endothelial progenitor cells (EPC) and the vascular endothelial growth factor receptor (VEGFR) 2+ cells in the peripheral blood were increased in groups treated with AMD-3100. The expression of vascular endothelial growth factor (VEGF) was increased in response to expansion or AMD injection. The expression of stromal cell derived factor (SDF)-1 and VEGFR2 were increased only in unexpanded flap treated with AMD-3100. Treatment with AMD-3100 increased both the number and area of blood vessels. However, there were no statistically significant differences in the survival area or physiologic microcirculation in rats from the other groups. This endogenous neovascularization induced by AMD-3100 may be a result of the increase in both the area and number of vessels, as well as paracrine augmentation of the expression of VEGF and EPCs. However, the presence of a tissue expander under the flap could block the neovascularization between the flap and the recipient regardless of AMD-3100 treatment and expansion.

Can the TLR-4-mediated signaling pathway be "a key inflammatory promoter for sporadic TAA"?

Thoracic aorta shows with advancing age various changes and a progressive deterioration in structure and function. As a result, vascular remodeling (VR) and medial degeneration (MD) occur as pathological entities responsible principally for the sporadic TAA onset. Little is known about their genetic, molecular, and cellular mechanisms. Recent evidence is proposing the strong role of a chronic immune/inflammatory process in their evocation and progression. Thus, we evaluated the potential role of Toll like receptor- (TLR-) 4-mediated signaling pathway and its polymorphisms in sporadic TAA. Genetic, immunohistochemical, and biochemical analyses were assessed. Interestingly, the rs4986790 TLR4 polymorphism confers a higher susceptibility for sporadic TAA (OR = 14.4, P = 0.0008) and it represents, together with rs1799752 ACE, rs3918242 MMP-9, and rs2285053 MMP-2 SNPs, an independent sporadic TAA risk factor. In consistency with these data, a significant association was observed between their combined risk genotype and sporadic TAA. Cases bearing this risk genotype showed higher systemic inflammatory mediator levels, significant inflammatory/immune infiltrate, a typical MD phenotype, lower telomere length, and positive correlations with histopatological abnormalities, hypertension, smoking, and ageing. Thus, TLR4 pathway should seem to have a key role in sporadic TAA. It might represent a potential useful tool for preventing and monitoring sporadic TAA and developing personalized treatments.

Bone marrow-derived vascular modulatory cells in pulmonary arterial hypertension

Hematopoiesis and vascular homeostasis are closely linked to each other via subsets of circulating bone marrow-derived cells with potent activity to repair endothelial injury and promote angiogenesis. As a consequence, abnormalities in hematopoiesis will eventually affect vascular health. Pulmonary arterial hypertension (PAH) is a vascular disease characterized by severe remodeling of the pulmonary artery wall. Over the past decade, circulating hematopoietic cells have been assigned an increasing role in the remodeling, such that these cells have been used in new therapeutic strategies. More recently, research has been extended to the bone marrow where these cells originate to identify abnormalities in hematopoiesis that may underlie PAH. Here, we review the current literature and identify gaps in knowledge of the myeloid effects on PAH.

IFNα serum levels are associated with endothelial progenitor cells imbalance and disease features in rheumatoid arthritis patients

Introduction

IFNα has been largely implicated in the ethiopathogenesis of autoimmune diseases but only recently it has been linked to endothelial damage and accelerated atherosclerosis in autoimmunity. In addition, proinflammatory conditions are supposed to be implicated in the cardiovascular status of these patients. Since a role for IFNα in endothelial damage and impaired Endothelial Progenitor Cell (EPC) number and function has been reported in other diseases, we aimed to evaluate the potential associations of IFNα serum levels on EPC populations and cytokine profiles in Rheumatoid Arthritis (RA) patients.

Methods

pre-EPC, EPC and mature EPC (mEPC) populations were quantified by flow cytometry analyzing their differential CD34, CD133 and VEGFR2 expression in blood samples from 120 RA patients, 52 healthy controls (HC), and 83 systemic lupus erythematosus (SLE) patients as disease control. Cytokine serum levels were measured by immunoassays and clinical and immunological data, including cardiovascular (CV) events and CV risk factors, were retrospectively obtained by reviewing clinical records.

Results

Long-standing, but not recent onset RA patients displayed a significant depletion of all endothelial progenitor populations, unless high IFNα levels were present. In fact, the IFN^high RA patient group (n = 40, 33%), showed increased EPC levels, comparable to SLE patients. In addition, high IFNα serum levels were associated with higher disease activity (DAS28), presence of autoantibodies, higher levels of IL-1β, IL-6, IL-10 and MIP-1α, lower amounts of TGF-β, and increased mEPC/EPC ratio, thus suggesting higher rates of endothelial damage and an endothelial repair failure. Finally, the relationship between high IFNα levels and occurrence of CV events observed in RA patients seems to support this hypothesis.

Conclusions

IFNα serum marker could be used to identify a group of RA patients with increased disease activity, EPC imbalance, enhanced proinflammatory profile and higher cardiovascular risk, probably due, at least in part, to an impaired endothelial repair.

How to utilize Ca²⁺ signals to rejuvenate the repairative phenotype of senescent endothelial progenitor cells in elderly patients affected by cardiovascular diseases: a useful therapeutic support of surgical approach?

Endothelial dysfunction or loss is the early event that leads to a host of severe cardiovascular diseases, such as atherosclerosis, hypertension, brain stroke, myocardial infarction, and peripheral artery disease. Ageing is regarded among the most detrimental risk factor for vascular endothelium and predisposes the subject to atheroscleorosis and inflammatory states even in absence of traditional comorbid conditions. Standard treatment to restore blood perfusion through stenotic arteries are surgical or endovascular revascularization. Unfortunately, ageing patients are not the most amenable candidates for such interventions, due to high operative risk or unfavourable vascular involvement. It has recently been suggested that the transplantation of autologous bone marrow-derived endothelial progenitor cells (EPCs) might constitute an alternative and viable therapeutic option for these individuals. Albeit pre-clinical studies demonstrated the feasibility of EPC-based therapy to recapitulate the diseased vasculature of young and healthy animals, clinical studies provided less impressive results in old ischemic human patients. One hurdle associated to this kind of approach is the senescence of autologous EPCs, which are less abundant in peripheral blood and display a reduced pro-angiogenic activity. Conversely, umbilical cord blood (UCB)-derived EPCs are more suitable for cellular therapeutics due to their higher frequency and sensitivity to growth factors, such as vascular endothelial growth factor (VEGF). An increase in intracellular Ca²⁺ concentration is central to EPC activation by VEGF. We have recently demonstrated that the Ca²⁺ signalling machinery driving the oscillatory Ca²⁺ response to this important growth factor is different in UCB-derived EPCs as compared to their peripheral counterparts. In particular, we focussed on the so-called endothelial colony forming cells (ECFCs), which are the only EPC population belonging to the endothelial lineage and able to form capillary-like structures in vitro and stably integrate with host vasculature in vivo. The present review provides a brief description of how exploiting the Ca²⁺ toolkit of juvenile EPCs to restore the repairative phenotype of senescent EPCs to enhance their regenerative outcome in therapeutic settings.

Canonical transient receptor potential 3 channel triggers vascular endothelial growth factor-induced intracellular Ca2+ oscillations in endothelial progenitor cells isolated from umbilical cord blood

Endothelial colony-forming cells (ECFCs) are the only endothelial progenitor cells (EPCs) that are capable of acquiring a mature endothelial phenotype. ECFCs are mainly mobilized from bone marrow to promote vascularization and represent a promising tool for cell-based therapy of severe ischemic diseases. Vascular endothelial growth factor (VEGF) stimulates the proliferation of peripheral blood-derived ECFCs (PB-ECFCs) through oscillations in intracellular Ca(2+) concentration ([Ca(2+)]i). VEGF-induced Ca(2+) spikes are driven by the interplay between inositol-1,4,5-trisphosphate (InsP3)-dependent Ca(2+) release and store-operated Ca(2+) entry (SOCE). The therapeutic potential of umbilical cord blood-derived ECFCs (UCB-ECFCs) has also been shown in recent studies. However, VEGF-induced proliferation of UCB-ECFCs is faster compared with their peripheral counterpart. Unlike PB-ECFCs, UCB-ECFCs express canonical transient receptor potential channel 3 (TRPC3) that mediates diacylglycerol-dependent Ca(2+) entry. The present study aimed at investigating whether the higher proliferative potential of UCB-ECFCs was associated to any difference in the molecular underpinnings of their Ca(2+) response to VEGF. We found that VEGF induces oscillations in [Ca(2+)]i that are patterned by the interaction between InsP3-dependent Ca(2+) release and SOCE. Unlike PB-ECFCs, VEGF-evoked Ca(2+) oscillations do not arise in the absence of extracellular Ca(2+) entry and after pharmacological (with Pyr3 and flufenamic acid) and genetic (by employing selective small interference RNA) suppression of TRPC3. VEGF-induced UCB-ECFC proliferation is abrogated on inhibition of the intracellular Ca(2+) spikes. Therefore, the Ca(2+) response to VEGF in UCB-ECFCs is shaped by a different Ca(2+) machinery as compared with PB-ECFCs, and TRPC3 stands out as a promising target in EPC-based treatment of ischemic pathologies.

Regular exercise-induced increased number and activity of circulating endothelial progenitor cells attenuates age-related decline in arterial elasticity in healthy men

BACKGROUND

Deficiency in number and activity of circulating EPCs is associated with reduced arterial elasticity in humans with advancing aging. Physical exercise can increase the number and activity of circulating EPCs in humans. Here we investigated whether regular exercise-induced enhanced circulating endothelial progenitor cells (EPCs) improves age-related decline in arterial elasticity in healthy men.

METHODS

In a cross-sectional study, the number and activity of circulating EPCs as well as brachial-ankle pulse wave velocity (baPWV) of young and older sedentary or endurance-trained healthy men were studied. Then we observed the effect of regular exercise on circulating EPCs and baPWV of 10 older and 10 young sedentary healthy men.

RESULTS

In both sedentary and endurance-trained men, the number and activity of circulating EPCs were significantly low in older men compared with young men, which was paralleled to increased baPWV. After three months of regular exercise, the number and activity of circulating EPCs increased, and the baPWV of 10 older and 10 young sedentary healthy men decreased. However, the increased number and activity of circulating EPCs and decreased baPWV of older sedentary healthy men were higher. There was a close correlation between circulating EPCs and baPWV. Multivariate analysis identified proliferative activity of circulating EPCs as an independent predictor of baPWV.

CONCLUSIONS

The present study demonstrates for the first time that regular physical exercise-induced enhanced circulating EPCs attenuates age-related decline in arterial elasticity in healthy men. These findings provide novel insights into the protective effects of exercise on age-related vascular injury.

Vascular endothelial growth factor stimulates endothelial colony forming cells proliferation and tubulogenesis by inducing oscillations in intracellular Ca2+ concentration

Endothelial progenitor cells (EPCs) home from the bone marrow to the site of tissue regeneration and sustain neovascularization after acute vascular injury and upon the angiogenic switch in solid tumors. Therefore, they represent a suitable tool for cell-based therapy (CBT) in regenerative medicine and provide a novel promising target in the fight against cancer. Intracellular Ca(2+) signals regulate numerous endothelial functions, such as proliferation and tubulogenesis. The growth of endothelial colony forming cells (ECFCs), which are EPCs capable of acquiring a mature endothelial phenotype, is governed by store-dependent Ca(2+) entry (SOCE). This study aimed at investigating the nature and the role of VEGF-elicited Ca(2+) signals in ECFCs. VEGF induced asynchronous Ca(2+) oscillations, whose latency, amplitude, and frequency were correlated to the growth factor dose. Removal of external Ca(2+) (0Ca(2+)) and SOCE inhibition with N-(4-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]phenyl)-4-methyl-1,2,3-thiadiazole-5-carboxamide (BTP-2) reduced the duration of the oscillatory signal. Blockade of phospholipase C-γ with U73122, emptying the inositol-1,4,5-trisphosphate (InsP(3))-sensitive Ca(2+) pools with cyclopiazonic acid (CPA), and inhibition of InsP(3) receptors with 2-APB prevented the Ca(2+) response to VEGF. VEGF-induced ECFC proliferation and tubulogenesis were inhibited by the Ca(2+)-chelant, BAPTA, and BTP-2. NF-κB activation by VEGF was impaired by BAPTA, BTP-2, and its selective blocker, thymoquinone. Thymoquinone, in turn, suppressed VEGF-dependent ECFC proliferation and tubulogenesis. These data indicate that VEGF-induced Ca(2+) oscillations require the interplay between InsP(3)-dependent Ca(2+) release and SOCE, and promote ECFC growth and tubulogenesis by engaging NF-κB. This novel signaling pathway might be exploited to enhance the outcome of CBT and chemotherapy.

Human progenitor-derived endothelial cells vs. venous endothelial cells for vascular tissue engineering: an in vitro study

The isolation of endothelial progenitor cells from human peripheral blood generates a great hope in vascular tissue engineering because of particular benefit when compared with mature endothelial cells. We explored the capability of progenitor-derived endothelial cells (PDECs) to line fibrin and collagen scaffolds in comparison with human saphenous and umbilical cord vein endothelial cells (HSVECs and HUVECs): (a) in a static situation, allowing definition of the optimal cell culture conditions with different media and cell-seeding densities to check cell behaviour; (b) under shear stress conditions (flow chambers or tubular vascular constructs), allowing investigation of cell response and mRNA expression on both substrates by oligonucleotide microarray analysis and quantitative real-time PCR. Well characterized PDECs: (a) could not be expanded adequately with the usual mature ECs culture media; (b) were able to colonize and grow on fibrin glue; (c) exhibited higher resistance to oxidative stress than HSVECs and HUVECs; (d) withstood physiological shear stress when lining both substrates in flow chambers, and their gene expression was regulated; (e) colonized a collagen-impregnated vascular prosthesis and were able to sense mechanical forces. Our results provide an improved qualification of PDECs for vascular tissue engineering.

Hemopoietic and angiogenetic progenitors in healthy athletes: different responses to endurance and maximal exercise

The effects of endurance or maximal exercise on mobilization of bone marrow-derived hemopoietic and angiogenetic progenitors in healthy subjects are poorly defined. In 10 healthy amateur runners, we collected venous blood before, at the end of, and the day after a marathon race (n = 9), and before and at the end of a 1.5-km field test (n = 8), and measured hemopoietic and angiogenetic progenitors by flow cytometry and culture assays, as well as plasma or serum concentrations of several cytokines/growth factors. After the marathon, CD34(+) cells were unchanged, whereas clonogenetic assays showed decreased number of colonies for both erythropoietic (BFU-E) and granulocyte-monocyte (CFU-GM) series, returning to baseline the morning post-race. Conversely, CD34(+) cells, BFU-E, and CFU-GM increased after the field test. Angiogenetic progenitors, assessed as CD34(+)KDR(+) and CD133(+)VE-cadherin(+) cells or as adherent cells in culture expressing endothelial markers, increased after both endurance and maximal exercise but showed a different pattern between protocols. Interleukin-6 increased more after the marathon than after the field test, whereas hepatocyte growth factor and stem cell factor increased similarly in both protocols. Plasma levels of angiopoietin (Ang) 1 and 2 increased after both types of exercise, whereas the Ang-1-to-Ang-2 ratio or vascular endothelial growth factor-A were little affected. These data suggest that circulating hemopoietic progenitors may be utilized in peripheral tissues during prolonged endurance exercise. Endothelial progenitor mobilization after exercise in healthy trained subjects appears modulated by the type of exercise. Exercise-induced increase in growth factors suggests a physiological trophic effect of exercise on the bone marrow.

From cancer patients to cancer survivors: the issue of Cardioncology--a biological perspective

Long-term survival of cancer patients can be worsened by cardiovascular morbidity and mortality due to anticancer treatments based on cardiotoxic or antiangiogenic regimens. Growing scientific evidences support a role for circulating endothelial progenitor cells (EPCs) both in cancer pathogenesis and in cardiovascular diseases. High frequency of circulating EPCs seems to play a role in cancer growth and dissemination by favouring tumor angiogenesis and estabilishment of sites of metastasis. On the other hand, high level of circulating EPCs seems to be associated with a lower risk of developing cardiovascular diseases and with improved vascular regeneration after cardiovascular damage. Here, the possibile opposing roles of circulating EPCs in cancer patients suffering from therapy related-cardiovascular diseases are discussed, under the light of the potential modulation of their levels for therapeutic purposes. This can become a relevant issue in the field of cardioncology, the discipline that deals with the managing and treatment of cancer patients suffering from concomitant cardiovascular diseases or who are exposed to an increased risk to develop therapy related-cardiovascular complications.

The definition of EPCs and other bone marrow cells contributing to neoangiogenesis and tumor growth: is there common ground for understanding the roles of numerous marrow-derived cells in the neoangiogenic process?

Interest in the regulation of blood vessel formation as a mechanism to permit unregulated tumor cell growth was a prescient hypothesis of Dr. Judah Folkman nearly 3 decades ago. Understanding the cellular and molecular mechanisms that affect the recruitment, expansion, and turnover of the tumor microvasculature continues to evolve. While the fundamental paradigms for improving blood flow to growing, injured, diseased, or tumor infiltrated tissues are well known, the potential role of bone marrow derived circulating endothelial progenitor cells (EPCs) to function as postnatal vasculogenic precursors for tumor microvasculature has become a controversial premise. We will briefly review some recently published high profile papers that appear to derive polar interpretations for the role of EPCs in the angiogenic switch and discuss possible reasons for the disparate views in work conducted in both mouse and man.

Defining human endothelial progenitor cells

There is no specific marker to identify an endothelial progenitor cell (EPC) and this deficiency is restricting the ability of an entire field of research in defining these cells. We will review current methods to define EPC in the human system and suggest approaches to define better the cell populations involved in neoangiogenesis. PubMed was used to identify articles via the search term 'endothelial progenitor cell' and those articles focused on defining the term were evaluated. The only human cells expressing the characteristics of an EPC, as originally proposed, are endothelial colony forming cells. A variety of hematopoietic cells including stem and progenitors, participate in initiating and modulating neoangiogenesis. Future studies must focus on defining the specific hematopoietic subsets that are involved in activating, recruiting, and remodeling the vascular networks formed by the endothelial colony forming cells.

Long-term secondary prevention programs after cardiac rehabilitation for the reduction of future cardiovascular events: focus on regular physical activity

Cardiac rehabilitation/secondary prevention programs are recognized as integral to the comprehensive care of patients with coronary heart disease, and as such are recommended in most contemporary clinical practice guidelines. The interventions are aimed at reducing disability, optimizing cardiovascular risk reduction by drug therapy and promoting healthy behavior. Healthy lifestyle habits must be recognized as capable of substantially reducing the risk for cardiovascular events in patients with coronary heart disease. This review highlights the recommended components of cardiac rehabilitation/secondary prevention programs, with special emphasis on regular physical activity.

Endothelial progenitor cell-based neovascularization: implications for therapy

Ischemic cardiovascular events are a major cause of death globally. Endothelial progenitor cell (EPC)-based approaches can result in improvement of vascular perfusion and might offer clinical benefit. However, although functional improvement is observed, the lack of long-term engraftment of EPCs into neovessels has raised controversy regarding their mechanism of action. We and others have hypothesized that after ischemic injury, EPCs induce neovascularization through the secretion of cytokines and growth factors, which act in a paracrine fashion and induce sprouting angiogenesis by the surrounding endothelium. In this concise review, we discuss the (patho)physiology of EPC-induced neovascularization and focus on the paracrine signals secreted by EPCs and the effects they elicit. In future therapies, clinical administration of these paracrine modulators using slow-release depots might induce neovascularization and might therefore hold promise for vascular regenerative medicine.