Aging and hypertension are independent risk factors for reduced number of circulating endothelial progenitor cells

Transdermal Nicotine Patch Increases the Number and Function of Endothelial Progenitor Cells in Young Healthy Nonsmokers without Adverse Hemodynamic Effects

Transdermal nicotine patches (TNPs), administering nicotine into the bloodstream through skin, have been widely used as nicotine replacement therapy, and exposure to nicotine can be detected by measurement of plasma cotinine concentration. In animal studies, nicotine treatment could increase the number of endothelial progenitor cells (EPCs), but the effect of TNPs on circulating EPCs and their activity in humans remained unclear. This study aimed to explore the influence of TNPs on circulating EPCs with surface markers of CD34, CD133, and/or KDR, and colony-forming function plus migration activity of early EPCs derived from cultured peripheral blood mononuclear cells before and after TNP treatments in young healthy nonsmokers. In parallel, pulse wave analysis (PWA) was applied to evaluate the vascular effect of TNP treatments. Twenty-one participants (25.8 ± 3.6 years old, 10 males) used TNP (nicotine: 4.2 mg/day) for 7 consecutive days. During the treatment, the CD34+ EPCs progressively increased in number. In addition, the number of EPCs positive for CD34/KDR, CD133, and CD34/CD133 were also increased on day 7 of the treatment. Furthermore, the early EPC colony-forming function and migration activity were increased with the plasma cotinine level positively correlating with change in colony-forming unit number. PWA analyses on day 7, compared with pretreatment, did not show significant change except diastolic pressure time index, which was prolonged and implied potential vascular benefit. In conclusion, 7-day TNP treatments could be a practical strategy to enhance angiogenesis of circulating EPCs to alleviate tissue ischemia without any hemodynamic concern.

Senescence induces miR-409 to down-regulate CCL5 and impairs angiogenesis in endothelial progenitor cells

This study explores the impact of senescence on autocrine C-C motif chemokine ligand 5 (CCL5) in human endothelial progenitor cell (EPCs), addressing the poorly understood decline in number and function of EPCs during ageing. We examined the effects of replication-induced senescence on CCL5/CCL5 receptor (CCR5) signalling and angiogenic activity of EPCs in vitro and in vivo. We also explored microRNAs controlling CCL5 secretion in senescent EPCs, its impact on EPC angiogenic activity, and validated our findings in humans. CCL5 secretion and CCR5 levels in senescent EPCs were reduced, leading to attenuated angiogenic activity. CCL5 enhanced EPC proliferation via the CCR5/AKT/P70S6K axis and increased vascular endothelial growth factor (VEGF) secretion. Up-regulation of miR-409 in senescent EPCs resulted in decreased CCL5 secretion, inhibiting the angiogenic activity, though these negative effects were counteracted by the addition of CCL5 and VEGF. In a mouse hind limb ischemia model, CCL5 improved the angiogenic activity of senescent EPCs. Analysis involving 62 healthy donors revealed a negative association between CCL5 levels, age and Framingham Risk Score. These findings propose CCL5 as a potential biomarker for detection of EPC senescence and cardiovascular risk assessment, suggesting its therapeutic potential for age-related cardiovascular disorders.

Prognostic Value of Endothelial Progenitor Cells in Acute Myocardial Infarction Patients

Objective

To determine prognostic role of endothelial progenitor cells (EPCs) in intensive care patients with acute myocardial infarction (AMI).

Materials and Methods

From December 2018 to July 2021, a total of 91 eligible patients with AMI were consecutively examined in a single intensive care unit (ICU) in China. Patients with a history of acute coronary artery disease were excluded from the study. Samples were collected within 24 hr of onset of symptoms. EPCs, defined as coexpression of CD34+/CD133+ cells or CD133+/CD34+/KDR+, were studied using flow cytometry and categorized by quartiles. Based on the 28-days mortality outcome, the patients were further divided into two groups: death and survival. The study incorporated various variables, including cardiovascular risk factors such as body mass index, hypertension, diabetes, hypercholesterolemia, atherosclerotic burden, and medication history, as well as clinical characteristics such as APACHEⅡscore, central venous-arterial carbon dioxide difference (GAP), homocysteine, creatinine, C-reactive protein, HbAlc, and cardiac index. Cox regression analysis was employed to conduct a multivariate analysis.

Results

A total of 91 patients with AMI who were admitted to the ICU were deemed eligible for inclusion in the study. Among these patients, 23 (25.3%) died from various causes during the follow-up period. The counts of EPCs were found to be significantly higher in the survival group compared to the death group (P < 0.05). In the univariate analysis, it was observed that the 28-days mortality rate was associated with the several factors, including the APACHEⅡscore (P=0.00), vasoactive inotropic score (P=0.03), GAP (P=0.00), HCY (P=0.00), creatinine (P=0.00), C-reactive protein (P=0.00), HbAlc (P=0.00), CI (P=0.01), quartiles of CD34+/CD133+ cells (P=0.00), and quartiles of CD34+/CD133+/KDR+ cells (P=0.00). CD34+/CD133+/KDR+ cells retained statistical significance in Cox regression models even after controlling for clinical variables (HR: 6.258 × 10-10 and P=0.001). Nevertheless, no significant correlation was observed between CD34+/CD133+ cells and all-cause mortality.

Conclusions

The decreased EPCs levels, especially for CD34+/CD133+/KDR+ cells subsets, were an independent risk factor for 28-days mortality in AMI patients.

Beyond brain injury biomarkers: chemoattractants and circulating progenitor cells as biomarkers of endogenous rehabilitation effort in preterm neonates with encephalopathy

Introduction

Preclinical work and studies in adults have shown that endogenous regeneration efforts that involve mobilization of progenitor cells take place after brain injury. However, kinetics of endogenous circulating progenitor cells (CPCs) in preterm neonates is not well described, particularly their possible role regarding brain injury and regeneration. We aimed to assess the kinetics of CPCs in neonates with encephalopathy of prematurity in relation to brain injury biomarkers, chemoattractants and relevant antenatal and postanal clinical factors, in an effort to outline the related pathophysiology.

Materials and methods

47 preterm neonates (of 28-33 weeks GA) were enrolled: 31 newborns with no or minimal brain injury (grade I IVH) and 16 prematures with encephalopathy (grade III or IV IVH, PVL or infarct). Peripheral blood samples obtained on days 1, 3, 9, 18 and 45 after birth were analyzed using flow cytometry, focusing on EPCs (early and late Endothelial Progenitor Cells), HSCs (Hematopoietic Stem Cells) and VSELs (Very Small Embryonic-Like Stem Cells). At the same time-points serum levels of S100B, Neuron-specific Enolase (NSE), Erythropoietin (EPO), Insulin-like growth factor-1 (IGF-1) and SDF-1 were also measured. Neonates were assessed postnatally with brain MRI, and with Bayley III developmental test at 2 years of corrected age.

Results

Preterms with brain injury proved to have significant increase of S100B and NSE, followed by increase of EPO and enhanced mobilization mainly of HSCs, eEPCs and lEPCs. IGF-1 was rather decreased in this group of neonates. IGF-1 and most CPCs were intense decreased in cases of antenatal or postnatal inflammation. S100B and NSE correlated with neuroimaging and language scale in Bayley III test, providing good prognostic ability.

Conclusion

The observed pattern of CPCs' mobilization and its association with neurotrophic factors following preterm brain injury indicate the existence of an endogenous brain regeneration process. Kinetics of different biomarkers and associations with clinical factors contribute to the understanding of the related pathophysiology and might help to early discriminate neonates with adverse outcome. Timely appropriate enhancement of the endogenous regeneration effort, when it is suppressed and insufficient, using neurotrophic factors and exogenous progenitor cells might be a powerful therapeutic strategy in the future to restore brain damage and improve the neurodevelopmental outcome in premature infants with brain injury.

Hypertension and cellular senescence

Essential or primary hypertension is a wordwide health problem. Elevated blood pressure (BP) is closely associated not only with increased chronological aging but also with biological aging. There are various common pathways that play a role in cellular aging and BP regulation. These include but not limited to inflammation, oxidative stress, mitochondrial dysfunction, air pollution, decreased klotho activity increased renin angiotensin system activation, gut dysbiosis etc. It has already been shown that some anti-hypertensive drugs have anti-senescent actions and some senolytic drugs have BP lowering effects. In this review, we have summarized the common mechanisms underlying cellular senescence and HT and their relationships. We further reviewed the effect of various antihypertensive medications on cellular senescence and suggest further issues to be studied.

Royal Jelly Increases Hematopoietic Stem Cells in Peripheral Blood: A Double-Blind, Placebo-Controlled, Randomized Trial in Healthy Subjects

Objectives

Royal jelly (RJ), produced by honeybees, influences stem cell functions, such as pluripotency maintenance of mouse embryonic stem cells and prevention of aging-related muscle stem cell functional deterioration. Thus, we hypothesized that RJ administration has various health-promoting effects based on stem cells. However, its effects are unknown in humans. In this study, we have attempted for the first time to clarify whether the administration of RJ in humans affects stem cells.

Materials and Methods

This randomized, double-blind, placebo-controlled study was performed on healthy subjects (n = 90) who received protease-treated RJ at a dose of 1200 mg/day or placebo daily for four weeks. Also, the participants with a low number of hematopoietic stem cells (HSCs) in peripheral blood were preferentially selected. HSC counts, endothelial progenitor cell (EPC) counts, blood cell counts in peripheral blood, cytokines in serum, and physical conditions were evaluated. Results and Conclusion. Eligible data from 86 subjects (placebo: 42, RJ: 44) who completed the study were analyzed. There were no significant differences between the two groups regarding the changes in peripheral HSC count (p=0.103), while diastolic blood pressure showed a significant improvement in the RJ group compared to that in the placebo group (p=0.032). The subgroup analysis excluded 14 subjects who complained of cold symptoms at baseline or within five days of the four-week study. The changes in the HSC populations were significantly higher in the RJ group than those in the placebo group (p=0.042). No adverse effects were observed in any of the groups. These results suggest that RJ administration affected the peripheral HSC count and may influence stem cell functions. Further research is needed to reveal the various health-promoting benefits of RJ based on stem cells.

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.

Endothelial Progenitor Cells in Neurovascular Disorders—A Comprehensive Overview of the Current State of Knowledge

Endothelial progenitor cells (EPCs) are a population of cells that circulate in the blood looking for areas of endothelial or vascular injury in order to repair them. Endothelial dysfunction is an important component of disorders with neurovascular involvement. Thus, the subject of involvement of EPCs in such conditions has been gaining increasing scientific interest in recent years. Overall, decreased levels of EPCs are associated with worse disease outcome. Moreover, their functionalities appear to decline with severity of disease. These findings inspired the application of EPCs as therapeutic targets and agents. So far, EPCs appear safe and promising based on the results of pre-clinical studies conducted on their use in the treatment of Alzheimer’s disease and ischemic stroke. In the case of the latter, human clinical trials have recently started to be performed in this subject and provided optimistic results thus far. Whereas in the case of migraine, existing findings pave the way for testing EPCs in in vitro studies. This review aims to thoroughly summarize current knowledge on the role EPCs in four disorders with neurovascular involvement, which are Alzheimer’s disease, cerebral small vessel disease, ischemic stroke and migraine, with a particular focus on the potential practical use of these cells as a treatment remedy.

Transforming growth factor-β1/Thrombospondin-1/CD47 axis mediates dysfunction in CD34+ cells derived from diabetic older adults

Aging with diabetes is associated with impaired vasoprotective functions and decreased nitric oxide (NO) generation in CD34+ cells. Transforming growth factor- β1 (TGF-β1) is known to regulate hematopoietic functions. This study tested the hypothesis that transforming growth factor- β1 (TGF-β1) is upregulated in diabetic CD34+ cells and impairs NO generation via thrombospondin-1 (TSP-1)/CD47/NO pathway. CD34+ cells from nondiabetic (ND) (n=58) or diabetic older adults (DB) (both type 1 and type 2) (n=62) were isolated from peripheral blood. TGF-β1 was silenced by using an antisense delivered as phosphorodiamidate morpholino oligomer (PMO-TGF-β1). Migration and proliferation in response to stromal-derived factor-1α (SDF-1α) were evaluated. NO generation and eNOS phosphorylation were determined by flow cytometry. CD34+ cells from older, but not younger, diabetics have higher expression of TGF-β1 compared to that observed in cells derived from healthy individuals (P<0.05, n=14). TSP-1 expression was higher (n=11) in DB compared to ND cells. TGFβ1-PMO decreased the secretion of TGF-β1, which was accompanied with decreased TSP-1 expression. Impaired proliferation, migration and NO generation in response to SDF-1α in DB cells were reversed by TGF-β1-PMO (n=6). TSP-1 inhibited migration and proliferation of nondiabetic CD34+ cells that was reversed by CD47-siRNA, which also restored these responses in diabetic CD34+ cells. TSP-1 opposed SDF-1α-induced eNOS phosphorylation at Ser1177 that was reversed by CD47-siRNA. These results infer that increased TGF-β1 expression in CD34+ cells induces dysfunction in CD34+ cells from diabetic older adults via TSP-1/CD47-dependent inhibition of NO generation.

Pitavastatin activates mitophagy to protect EPC proliferation through a calcium-dependent CAMK1-PINK1 pathway in atherosclerotic mice

Statins play a major role in reducing circulating cholesterol levels and are widely used to prevent coronary artery disease. Although they are recently confirmed to up-regulate mitophagy, little is known about the molecular mechanisms and its effect on endothelial progenitor cell (EPC). Here, we explore the role and mechanism underlying statin (pitavastatin, PTV)-activated mitophagy in EPC proliferation. ApoE^−/− mice are fed a high-fat diet for 8 weeks to induce atherosclerosis. In these mice, EPC proliferation decreases and is accompanied by mitochondrial dysfunction and mitophagy impairment via the PINK1-PARK2 pathway. PTV reverses mitophagy and reduction in proliferation. Pink1 knockout or silencing Atg7 blocks PTV-induced proliferation improvement, suggesting that mitophagy contributes to the EPC proliferation increase. PTV elicits mitochondrial calcium release into the cytoplasm and further phosphorylates CAMK1. Phosphorylated CAMK1 contributes to PINK1 phosphorylation as well as mitophagy and mitochondrial function recover in EPCs. Together, our findings describe a molecular mechanism of mitophagy activation, where mitochondrial calcium release promotes CAMK1 phosphorylation of threonine¹⁷⁷ before phosphorylation of PINK1 at serine²²⁸, which recruits PARK2 and phosphorylates its serine⁶⁵ to activate mitophagy. Our results further account for the pleiotropic effects of statins on the cardiovascular system and provide a promising and potential therapeutic target for atherosclerosis.

Endothelial progenitor cell (EPCs) proliferation decreased, accompanied by mitochondrial dysfunction and mitophagy impairment via the PINK1-PARK2 pathway in atherosclerosis. Statins induce mitophagy to protect EPCs by mitochondrial calcium release and CAMK1-mediated PINK1 phosphorylation.

Early onset of aging phenotype in vascular repair by Mas receptor deficiency

Aging is associated with impaired vascular repair following ischemic insult, largely due to reparative dysfunctions of progenitor cells. Activation of Mas receptor (MasR) was shown to reverse aging-associated vasoreparative dysfunction. This study tested the impact of MasR-deficiency on mobilization and vasoreparative functions with aging. Wild type (WT) or MasR-deficient mice (MasR^-/- or MasR^+/-) at 12-14 weeks (young) or middle age (11-12 months) (MA) were used in the study. Mobilization of lineage-negative, Sca-1-positive cKit-positive (LSK) cells in response to G-CSF or plerixafor was determined. Hindlimb ischemia (HLI) was induced by femoral artery ligation. Mobilization and blood flow recovery were monitored post-HLI. Radiation chimeras were made by lethal irradiation of WT or MasR^-/- mice followed by administration of bone marrow cells from MasR^-/- or WT mice, respectively. Nitric oxide (NO) generation by stromal-derived factor-1α (SDF) and mitochondrial reactive oxygen species (mitoROS) levels were determined by flow cytometry. Effect of A779 treatment on mobilization, blood flow recovery, and NO and ROS levels were determined in young WT and MasR^+/- mice. Circulating LSK cells in basal or in response to plerixafor or G-CSF or in response to ischemic injury were lower in MasR^-/- mice compared to the WT. Responses in MasR^+/- mice were similar to the WT at young age but at the middle age, impairments were observed. Impaired mobilization to ischemia or G-CSF was rescued in WT → MasR^-/- chimeras. NO levels were lower and mitoROS were higher in MasR^-/- LSK cells compared to WT cells. A779 precipitated dysfunctions in young-MasR^+/- mice similar to that observed in MA-MasR^+/-, and this accompanied decreased NO generation by SDF and enhanced mitoROS levels. This study shows that mice at MA do not exhibit vasoreparative dysfunction. Either partial or total loss of MasR precipitates advanced-aging phenotype likely due to lack of NO and oxidative stress.

Systemic cytology. A novel diagnostic approach for assessment of early systemic disease

Recognition of low grade or asymptomatic systemic diseases suggests prevention of the worst, yet has been proven challenging ever since. Biomarker-based liquid biopsy has emerged in recent years as a practical platform for the assessment of systemic diseases yet, technical realizations were mainly focused on cancer, faced challenges in accuracy at early stage and are lacking provision of sufficient evidence of disease. In particular in cell-based cancer liquid biopsy, obstacles are rarity and heterogeneity of circulating tumor and tumor-associated rare cells. Evidence is mounting about an entire spectrum of distinct circulating rare cell types that denotes the systemic component of a certain physiological state. Therefore, circulating rare cells in combination may arise from yet, also account for systemic diseases, which we denote as multi-rare cell association and involves foremost bone marrow-derived progenitor and stem cells yet, also matured somatic cell types. One would expect immense diagnostic value in the read-out of the so called rare cell population which represents cytological evidence of abnormality. We hypothesize that comprehensive rare cell population profiling as contrasted to the biomarker screening approach may realize the premise of a biopsy as to confirm, characterize, grade, stage or predict a systemic disease. This novel approach represents the "missing link" in diagnostic care of in particular early or residual systemic disease and presumes a steady gain in knowledge about the clinical interpretation of rare cell population profiles thus, expecting the knowledge-driven transformation of cell-based liquid biopsy from suggestion to confirmation. We support our hypothesis by past findings made by others and us and provide insights how to interpret a certain rare cell population profile.

Deferoxamine accelerates endothelial progenitor cell senescence and compromises angiogenesis

Senescence reduces the circulating number and angiogenic activity of endothelial progenitor cells (EPCs), and is associated with aging-related vascular diseases. However, it is very time-consuming to obtain aged cells (~1 month of repeated replication) or animals (~2 years) for senescence studies. Here, we established an accelerated senescence model by treating EPCs with deferoxamine (DFO), an FDA-approved iron chelator. Four days of low-dose (3 μM) DFO induced senescent phenotypes in EPCs, including a senescent pattern of protein expression, impaired mitochondrial bioenergetics, altered mitochondrial protein levels and compromised angiogenic activity. DFO-treated early EPCs from young and old donors (< 35 vs. > 70 years old) displayed similar senescent phenotypes, including elevated senescence-associated β-galactosidase activity and reduced relative telomere lengths, colony-forming units and adenosine triphosphate levels. To validate this accelerated senescence model in vivo, we intraperitoneally injected Sprague-Dawley rats with DFO for 4 weeks. Early EPCs from DFO-treated rats displayed profoundly senescent phenotypes compared to those from control rats. Additionally, in hind-limb ischemic mice, DFO pretreatment compromised EPC angiogenesis by reducing both blood perfusion and capillary density. DFO thus accelerates EPC senescence and appears to hasten model development for cellular senescence studies.

Mobilization of progenitor cells and vessel healing after implantation of SYNERGY in acute coronary syndrome

This study was aimed to compare the vascular healing process of a SYNERGY stent with that of a PROMUS PREMIER stent in patients with acute coronary syndrome (ACS). In 71 patients with ACS, undergoing coronary stent implantation using the SYNERGY stent (n = 52) or PROMUS PREMIER stent (n = 19), we measured circulating CD34+/CD133+/CD45^null cells and CD34+/KDR+ cells and observed vascular healing at the stented sites using optical coherence tomography (OCT) and coronary angioscopy. On the day 7, circulating CD34+/CD133+/CD45^null cells increased in SYNERGY group (P < 0.0001), while it did not change in PROMUS group. The CD34+/KDR+ cells also increased in SYNERGY group (P < 0.0001) but less significantly in the PROMUS group (P < 0.05). The OCT-based neointimal thickness (P < 0.0005) and neointimal coverage rate (P < 0.05) at 12 months were greater in SYNERGY group, compared with PROMUS group. The coronary angioscopy-based neointimal coverage grade at 12 months was also greater in SYNERGY group (P < 0.001). In overall patients, the change in CD34+/KDR+ cells on the day 7 correlated with the OCT-based neointimal thickness at 12 months (R = 0.288, P < 0.05). SYNERGY stent seems to have potential advantages over PROMUS PREMIER stent for ACS patients in terms of vascular healing process at the stented sites.

Increased circulating endothelial progenitor cells (EPCs) in prepubertal children born prematurely: a possible link between prematurity and cardiovascular risk

BACKGROUND

Endothelial progenitor cells (EPCs) ensure vascular integrity and neovascularization. No studies have investigated EPCs in preterm-born children beyond infancy.

METHODS

One hundred and thirty-six prepubertal children were enrolled: 63 preterm and 73 born at term (controls). Circulating CD34(+)/VEGFR-2(+)/CD45(-) and CD34(+)/VEGFR-2(+)/CD45dim EPCs were measured in preterm-born children compared to controls. Body mass index (BMI), waist-to-hip ratio (WHR), neck circumference, systolic and diastolic blood pressure (SBP and DBP, respectively), fasting glucose, insulin, lipid profile, common carotid and abdominal aortic intima-media thickness (cIMT and aIMT, respectively), endothelium-dependent brachial artery flow-mediated dilation (FMD), and echocardiographic parameters were also assessed.

RESULTS

Circulating CD34(+)/VEGFR-2(+)/CD45(-) and CD34(+)/VEGFR-2(+)/CD45dim EPCs were significantly higher in preterm-born children compared to controls (p < 0.001 and p < 0.001, respectively). In total study population and in the preterm-born group, EPCs were significantly lower in children born to mothers with gestational diabetes compared to non-diabetic mothers. Prematurity was associated with higher WHR, neck circumference, SBP, DBP, cIMT, aIMT, mean pressure, and velocity of pulmonary artery; the peak velocity of the brachial artery was significantly lower in children born prematurely. In multiple regression analysis, preterm birth and maternal gestational diabetes were recognized as independent predictors of EPCs.

CONCLUSIONS

Circulating EPCs were increased in prepubertal preterm-born children in comparison with peers born full-term. Maternal gestational diabetes was associated with a decrease in EPCs.

IMPACT

Mounting evidence supports the adverse effect of prematurity on cardiovascular health. However, the underlying mechanisms that could lead to endothelial dysfunction in preterm-born individuals are not fully understood. Endothelial progenitor cells (EPCs) ensure vascular integrity, normal endothelial function and neovascularization. No studies have investigated the EPCs counts in peripheral blood beyond infancy in children born prematurely. Circulating EPCs were significantly higher in preterm-born prepubertal children compared to controls, thus indicating that prematurity is possibly associated with endothelial damage. In total study population and in the preterm-born group, maternal gestational diabetes was associated with decreased EPCs concentrations.

Circulating Progenitor Cells Are Associated With Plaque Progression And Long-Term Outcomes In Heart Transplant Patients

AIMS

Circulating progenitor cells (CPCs) play a role in vascular repair and plaque stability, while osteocalcin (OC) expressing CPCs have been linked to unstable plaque and adverse cardiovascular outcomes. However, their role in cardiac allograft vasculopathy (CAV) has not been elucidated. This cohort study aimed to investigate the contribution of CPCs on CAV progression and cardiovascular events after heart transplantation.

METHODS AND RESULTS

A total of 80 heart transplant patients (mean age 55 ± 14 years, 72% male) undergoing annual intravascular ultrasound (IVUS) had fresh CPCs marked by CD34, CD133, and OC counted in peripheral blood using flow cytometry, on the same day as baseline IVUS. CAV progression was assessed by IVUS as the change (Δ) in plaque volume divided by segment length (PV/SL), adjusted for the time between IVUS measurements (median 3.0, interquartile range (IQR) [2.8, 3.1] years), and was defined as ΔPV/SL that is above the median ΔPV/SL of study population. Major adverse cardiac events (MACE) was defined as any incident of revascularization, myocardial infarction, heart failure admission, re-transplantation, stroke and death. Patients with higher CD34+CD133+ CPCs had a decreased risk of CAV progression (odds ratio 0.58, 95% confidence interval [CI] [0.37, 0.92], p = 0.01) and MACE (hazard ratio [HR] 0.79, 95% CI [0.66, 0.99], p = 0.05) during a median (IQR) follow up of 8.0 years (7.2, 8.3). Contrarily, higher OC+ cell counts were associated with an increased risk of MACE (HR 1.26, 95% CI [1.03, 1.57], p = 0.02).

CONCLUSIONS

Lower levels of CD34+CD133+ CPCs are associated with plaque progression and adverse long-term outcomes in patients who underwent allograft heart transplantation. In contrast, higher circulating OC+ levels are associated with adverse long term outcomes. Thus, CPCs might play a role in amelioration of transplant vasculopathy, while OC expression by these cells might play a role in progression.

TRANSLATIONAL PERSPECTIVE

The results of the current study suggest lower levels of circulating CD34+CD133+ cell levels are associated with cardiac allograft vasculopathy progression and future adverse cardiovascular events, while higher OC+ cell levels are associated with a greater risk of future cardiovascular events. Further studies confirming our findings might elucidate the role of circulating progenitor cells in the pathophysiology of CAV. Moreover, our findings might support the use of circulating progenitors as biomarkers, as well as the notion of cell therapy as potential treatment option for CAV, a disease with severe burden and limited treatment options.

In vitro recellularization of decellularized bovine carotid arteries using human endothelial colony forming cells

BACKGROUND

Many patients suffering from peripheral arterial disease (PAD) are dependent on bypass surgery. However, in some patients no suitable replacements (i.e. autologous or prosthetic bypass grafts) are available. Advances have been made to develop autologous tissue engineered vascular grafts (TEVG) using endothelial colony forming cells (ECFC) obtained by peripheral blood draw in large animal trials. Clinical translation of this technique, however, still requires additional data for usability of isolated ECFC from high cardiovascular risk patients. Bovine carotid arteries (BCA) were decellularized using a combined SDS (sodium dodecyl sulfate) -free mechanical-osmotic-enzymatic-detergent approach to show the feasibility of xenogenous vessel decellularization. Decellularized BCA chips were seeded with human ECFC, isolated from a high cardiovascular risk patient group, suffering from diabetes, hypertension and/or chronic renal failure. ECFC were cultured alone or in coculture with rat or human mesenchymal stromal cells (rMSC/hMSC). Decellularized BCA chips were evaluated for biochemical, histological and mechanical properties. Successful isolation of ECFC and recellularization capabilities were analyzed by histology.

RESULTS

Decellularized BCA showed retained extracellular matrix (ECM) composition and mechanical properties upon cell removal. Isolation of ECFC from the intended target group was successfully performed (80% isolation efficiency). Isolated cells showed a typical ECFC-phenotype. Upon recellularization, co-seeding of patient-isolated ECFC with rMSC/hMSC and further incubation was successful for 14 (n = 9) and 23 (n = 5) days. Reendothelialization (rMSC) and partial reendothelialization (hMSC) was achieved. Seeded cells were CD31 and vWF positive, however, human cells were detectable for up to 14 days in xenogenic cell-culture only. Seeding of ECFC without rMSC was not successful.

CONCLUSION

Using our refined decellularization process we generated easily obtainable TEVG with retained ECM- and mechanical quality, serving as a platform to develop small-diameter (< 6 mm) TEVG. ECFC isolation from the cardiovascular risk target group is possible and sufficient. Survival of diabetic ECFC appears to be highly dependent on perivascular support by rMSC/hMSC under static conditions. ECFC survival was limited to 14 days post seeding.

ACE2 gene transfer ameliorates vasoreparative dysfunction in CD34+ cells derived from diabetic older adults

Diabetes increases the risk for ischemic vascular diseases, which is further elevated in older adults. Bone marrow-derived hematopoietic CD34+ stem/progenitor cells have the potential of revascularization; however, diabetes attenuates vasoreparative functions. Angiotensin-converting enzyme 2 (ACE2) is the vasoprotective enzyme of renin-angiotensin system in contrast with the canonical angiotensin-converting enzyme (ACE). The present study tested the hypothesis that diabetic dysfunction is associated with ACE2/ACE imbalance in hematopoietic stem/progenitor cells (HSPCs) and that increasing ACE2 expression would restore reparative functions. Blood samples from male and female diabetic (n=71) or nondiabetic (n=62) individuals were obtained and CD34+ cells were enumerated by flow cytometry. ACE and ACE2 enzyme activities were determined in cell lysates. Lentiviral (LV) approach was used to increase the expression of soluble ACE2 protein. Cells from diabetic older adults (DB) or nondiabetic individuals (Control) were evaluated for their ability to stimulate revascularization in a mouse model of hindlimb ischemia (HLI). DB cells attenuated the recovery of blood flow to ischemic areas in nondiabetic mice compared with that observed with Control cells. Administration of DB cells modified with LV-ACE2 resulted in complete restoration of blood flow. HLI in diabetic mice resulted in poor recovery with amputations, which was not reversed by either Control or DB cells. LV-ACE2 modification of Control or DB cells resulted in blood flow recovery in diabetic mice. In vitro treatment with Ang-(1-7) modified paracrine profile in diabetic CD34+ cells. The present study suggests that vasoreparative dysfunction in CD34+ cells from diabetic older adults is associated with ACE2/ACE imbalance and that increased ACE2 expression enhances the revascularization potential.

ACE2/ACE imbalance and impaired vasoreparative functions of stem/progenitor cells in aging

Aging increases risk for ischemic vascular diseases. Bone marrow–derived hematopoietic stem/progenitor cells (HSPCs) are known to stimulate vascular regeneration. Activation of either the Mas receptor (MasR) by angiotensin-(1-7) (Ang-(1-7)) or angiotensin-converting enzyme-2 (ACE2) stimulates vasoreparative functions in HSPCs. This study tested if aging is associated with decreased ACE2 expression in HSPCs and if Ang-(1-7) restores vasoreparative functions. Flow cytometric enumeration of Lin⁻CD45^lowCD34⁺ cells was carried out in peripheral blood of male or female individuals (22–83 years of age). Activity of ACE2 or the classical angiotensin-converting enzyme (ACE) was determined in lysates of HSPCs. Lin⁻Sca-1⁺cKit⁺ (LSK) cells were isolated from young (3–5 months) or old (20–22 months) mice, and migration and proliferation were evaluated. Old mice were treated with Ang-(1-7), and mobilization of HSPCs was determined following ischemia induced by femoral ligation. A laser Doppler blood flow meter was used to determine blood flow. Aging was associated with decreased number (Spearman r = − 0.598, P < 0.0001, n = 56), decreased ACE2 (r = − 0.677, P < 0.0004), and increased ACE activity (r = 0.872, P < 0.0001) (n = 23) in HSPCs. Migration or proliferation of LSK cells in basal or in response to stromal-derived factor-1α in old cells is attenuated compared to young, and these dysfunctions were reversed by Ang-(1-7). Ischemia increased the number of circulating LSK cells in young mice, and blood flow to ischemic areas was recovered. These responses were impaired in old mice but were restored by treatment with Ang-(1-7). These results suggest that activation of ACE2 or MasR would be a promising approach for enhancing ischemic vascular repair in aging.

Exercise, Cardiovascular Health, and Risk Factors for Atherosclerosis: A Narrative Review on These Complex Relationships and Caveats of Literature

The following narrative review addresses the relationship between physical activity and exercise with cardiovascular health, focusing primarily on the following risk factors for atherosclerosis: hypertension, dyslipidemia, and vascular function. Cardiovascular diseases are intimately associated with mortality and morbidity, and current societal organization contributes to the incidence of cardiovascular events. A worldwide epidemiological transition to cardiovascular deaths was observed in the last century, with important decrements in physical activity and diet quality. An atherogenic environment started to be the new normal, with risk factors such as dyslipidemia, hypertension, and endothelial dysfunction observed in great portions of the population. Exercise is an important tool to improve overall health. For hypertension, a great amount of evidence now puts exercise as an effective therapeutic tool in the treatment of this condition. The effects of exercise in modifying blood lipid-lipoprotein are less clear. Despite the rationale remaining solid, methodological difficulties impair the interpretation of possible effects in these variables. Vascular function, as assessed by flow-mediated dilatation, is a good measure of overall vascular health and is consistently improved by exercise in many populations. However, in individuals with hypertension, the exercise literature still needs a further description of possible effects on vascular function variables. Physical activity and exercise are associated with improved cardiovascular health, especially with reduced blood pressure, and should be encouraged on the individual and population level. Evidence regarding its effects on blood lipids and flow-mediated dilatation still need solid landmark studies to guide clinical practice.

S-Phase Kinase-associated Protein-2 Rejuvenates Senescent Endothelial Progenitor Cells and Induces Angiogenesis in Vivo

Cell cycle slowdown or arrest is a prominent feature of cellular senescence. S-phase kinase-associated protein-2 (Skp2), an F-box subunit of SCF^Skp2 ubiquitin ligase, is a key regulator of G1/S transition. We investigated whether Skp2 plays a role in the regulation of endothelial progenitor cell (EPC) senescence, which is closely associated with aging-related vasculopathy. Replication-induced senescent EPCs demonstrated more pronounced senescence markers and lower Skp2 levels in comparison with those of their younger counterparts. Depletion of Skp2 induced increases in senescence-associated β-galactosidase (SA-βGal) activity and a reduction of telomere length and generated a senescent bioenergetics profile, whereas adenoviral-mediated Skp2 expression reversed the relevant senescence. EPCs isolated from older rats displayed a reduced proliferation rate and increased SA-βGal activity, both of which were significantly reversed by Skp2 ectopic expression. In addition to reversing senescence, Skp2 also rescued the angiogenic activity of senescent EPCs in the ischemic hind limbs of nude mice. The results revealed that ectopic expression of Skp2 has the potential to rejuvenate senescent EPCs and rescue their angiogenic activity and thus may be pivotal in the development of novel strategies to manage aging-related vascular disease.

The Protective Effect of Adiponectin-Transfected Endothelial Progenitor Cells on Cognitive Function in D-Galactose-Induced Aging Rats

Aging is a multifactorial process involving the cumulative effects of inflammation, oxidative stress, and mitochondrial dynamics, which can produce complex structural and biochemical alterations to the nervous system and lead to dysfunction of microcirculation, blood-brain barrier (BBB), and other problems in the brain. Long-term injection of D-galactose (D-gal) can induce chronic inflammation and oxidative stress, accelerating aging. The model of accelerated aging with long-term administration of D-gal have been widely used in anti-aging studies, due to the increase of chronic inflammation and decline of cognition that similarity with natural aging in animals. However, despite extensive researches in the D-gal-induced aging rats, studies on their microvasculature remain limited. Endothelial progenitor cells (EPCs), which are precursors to endothelial cells (ECs), play a significant role in the repair and regeneration process of endogenous blood vessel, and adiponectin (APN), a protein derived from adipocyte, has many effects on protective vascular endothelium and anti-inflammatory. Recently, many studies have shown that APN can promote improvements in cognitive function. Under these circumstances, we investigated the neuroprotective effect of the APN-transfected EPC (APN-EPC) treatment on rats after administration with D-gal and explored the likely underlying mechanisms. Compared to model group for D-gal administration, better cognitive function and denser microvessels were significantly found in the APN-EPC treatment group, and indicated APN-EPC treatment in aging rats could improve the cognitive dysfunction and microvessel density. The level of proinflammatory cytokines IL-1β, IL-6, and TNF-α, activated astrocytes and apoptosis rate were significantly reduced in the APN-EPC group compared with the model group, showed that APN-EPCs alleviated the neuroinflammation in aging rats. In addition, the APN-EPC group inhibited the decrease of BBB-related proteins claudin-5, occludin, and Zo-1 in aging rats and attenuated BBB dysfunction significantly. These results of our study indicated that APN-EPC treatment in D-gal-induced aging rats have a positive effect on improving cognitive and BBB dysfunction, increasing angiogenesis, and reducing neuroinflammation and apoptosis rate. This research suggests that cell therapy via gene modification may provide a safe and effective approach for the treatment of age-related neurogenerative diseases.

Rhynchophylline Attenuates Senescence of Endothelial Progenitor Cells by Enhancing Autophagy

The increase of blood pressure accelerates endothelial progenitor cells (EPCs) senescence, hence a significant reduction in the number of EPCs is common in patients with hypertension. Autophagy is a defense and stress regulation mechanism to assist cell homeostasis and organelle renewal. A growing number of studies have found that autophagy has a positive role in repairing vascular injury, but the potential mechanism between autophagy and senescence of EPCs induced by hypertension has rarely been studied. Therefore, in this study, we aim to explore the relationship between senescence and autophagy, and investigate the protective effect of rhynchophylline (Rhy) on EPCs. In angiotensin II (Ang II)-treated EPCs, enhancing autophagy through rapamycin mitigated Ang II-induced cell senescence, on the contrary, 3-methyladenine aggravated the senescence by weakening autophagy. Similarly, Rhy attenuated senescence and improved cellular function by rescuing the impaired autophagy in Ang II-treated EPCs. Furthermore, we found that Rhy promoted autophagy by activating AMP-activated protein kinase (AMPK) signaling pathway. Our results show that enhanced autophagy attenuates EPCs senescence and Rhy rescues autophagy impairment to protect EPCs against Ang II injury.

Changes of the coronary arteries and cardiac microvasculature with aging: Implications for translational research and clinical practice

Aging results in functional and structural changes in the cardiovascular system, translating into a progressive increase of mechanical vessel stiffness, due to a combination of changes in micro-RNA expression patterns, autophagy, arterial calcification, smooth muscle cell migration and proliferation. The two pivotal mechanisms of aging-related endothelial dysfunction are oxidative stress and inflammation, even in the absence of clinical disease. A comprehensive understanding of the aging process is emerging as a primary concern in literature, as vascular aging has recently become a target for prevention and treatment of cardiovascular disease. Change of life-style, diet, antioxidant regimens, anti-inflammatory treatments, senolytic drugs counteract the pro-aging pathways or target senescent cells modulating their detrimental effects. Such therapies aim to reduce the ineluctable burden of age and contrast aging-associated cardiovascular dysfunction. This narrative review intends to summarize the macrovascular and microvascular changes related with aging, as a better understanding of the pathways leading to arterial aging may contribute to design new mechanism-based therapeutic approaches to attenuate the features of vascular senescence and its clinical impact on the cardiovascular system.

Neointimal tissue characterization after implantation of drug-eluting stents by optical coherence tomography: quantitative analysis of optical density

Normalized optical density (NOD) measured by optical coherence tomography represents neointimal maturity after coronary stent implantation and is correlated with morphologic information provided by both light and electron microscopy. We aimed to test the hypothesis that even second generation drug-eluting stents (DESs) are problematic in terms of neointimal maturity. We implanted bare-metal stents (BMS: n = 14), everolimus-eluting stents (EESs: n = 15) or zotarolimus-eluting stents (ZESs: n = 12) at 41 sites in 32 patients with stable coronary artery disease. OCT was performed at up to 12 months of follow-up, and the average optical density of neointima covering struts was evaluated. NOD was calculated as the optical density of stent-strut covering tissue divided by the optical density of the struts. We also measured circulating CD34+ /CD133+ /CD45low cells, and serum levels of stromal cell-derived factor (SDF)-1, interleukin (IL)-8 and matrix metalloproteinase (MMP)-9 at baseline and follow-up. NOD was lower in the EES (0.70 ± 0.06) group than in the BMS (0.76 ± 0.07, P < 0.05) and ZES (0.76 ± 0.06, P < 0.05) groups. The mean neointimal area (R = 0.33, P < 0.05) and mean neointimal thickness (R = 0.37, P < 0.05) were correlated with NOD. Although NOD was not correlated with percent changes in circulating endothelial progenitor cells, and the levels of SDF-1 and IL-8, it was negatively correlated with the change in MMP-9 level (R = - 0.51, P < 0.01). Neointimal maturity might be lower at EES sites than BMS or ZES sites. This might lead to impaired neointimal tissue growth and matrix degradation. These results suggest a specific pathophysiology after DES implantation.

Rheumatoid arthritis (RA) and cardiovascular disease

Patients with rheumatoid arthritis (RA) suffer cardiovascular events 1.5-2 fold than the general population, and cardiovascular (CV) events are leading cause of death in patients with RA. It is known that patients with RA have endothelial dysfunction, related with impaired function of endothelial progenitor cells (EPCs). The mechanistic pathways leading to endothelial function are complicated, but understanding these mechanisms may open new frontiers of management and therapies to patients suffering from atherosclerosis. Inflammation is a key factor in atherosclerosis, including endothelial function, plaque stabilization and post infarct remodeling; thus, inhibition of TNF-α may affect the inflammatory burden and plaque vulnerability leading to less cardiovascular events and myocardial infarctions. An aggressive management of inflammation may lead to a significant improvement in the clinical cardiovascular outcome of patients with RA. The clinical evidence that showed a reduced risk of CV events following treatment with anti-inflammatory agents may suggest a new approach to treat atherosclerosis, i.e., inhibition of inflammation using biological medications that were primarily aimed to treat the high scale inflammation of RA and other autoimmune-inflammatory diseases, but may be useful also to prevent progression of atherosclerosis.

[Pathogenesis of endothelial dysfunction in cerebral atherosclerosis and their correction]

The authors review the studies on oxidative stress in the pathogenesis of cerebrovascular diseases (CVD) and highlight a contribution of endothelial dysfunction to the CVD development. Own experience of using divasa in patients of old and very old age with chronic CVD comorbid to cerebral atherosclerosis is described.

Bone marrow derived endothelial progenitor cells retain their phenotype and functions after a limited number of culture passages and cryopreservation

A critical limitation for tissue engineering and autologous therapeutic applications of bone marrow derived EPCs is their low frequency, which is even lower in number and activity level in patients with cardiovascular risk factors and other diseases. New strategies for obtaining and reserving sufficient ready-to-use EPCs for clinical use have hit major obstacles, because effects of serial passage and cryopreservation on EPC phenotype and functions are still needed to be explored. The present study aims at investigating effects of a limited number of culture passages as well as cryopreservation on EPC phenotype and functions. We isolated EPCs from rat bone marrow and cultured them up to passage 12 (totaling achievements of 40 population doublings). The phenotype and functions of fresh cultured and post-cryopreserved EPCs at passages 7 and 12, respectively, were evaluated. EPCs at passage 12 maintained the morphological characteristics, marker phenotype, Dil-ac-LDL uptake and FITC-UEA-1 binding functions, enhanced EPCs proliferation, tube formation and migration, but decreased CD133 expression compared with EPCs at passage 7. Cryopreservation caused limited impairment in EPC phenotype and functions. In brief, our results demonstrated that a limited number of culture passages and cryopreservation did not change EPC phenotype and functions, and can be used for the development of robust strategies and quality control criterion for obtaining sufficient and high-quality ready-to-use EPCs for tissue engineering and therapeutic applications.

MicroRNA-126 Priming Enhances Functions of Endothelial Progenitor Cells under Physiological and Hypoxic Conditions and Their Therapeutic Efficacy in Cerebral Ischemic Damage

Endothelial progenitor cells (EPCs) have shown the potential for treating ischemic stroke (IS), while microRNA-126 (miR-126) is reported to have beneficial effects on endothelial function and angiogenesis. In this study, we investigated the effects of miR-126 overexpression on EPCs and explore the efficacy of miR-126-primed EPCs (EPC^miR-126) in treating IS. The effects of miR-126 overexpression on EPC proliferation, migratory, tube formation capacity, reactive oxygen species (ROS) production, and nitric oxide (NO) generation were determined. In in vivo study, the effects of EPC^miR-126 on the cerebral blood flow (CBF), neurological deficit score (NDS), infarct volume, cerebral microvascular density (cMVD), and angiogenesis were determined. Moreover, the levels of circulating EPCs (cEPCs) and their contained miR-126 were measured. We found (1) miR-126 overexpression promoted the proliferation, migration, and tube formation abilities of EPCs; decreased ROS; and increased NO production of EPCs via activation of PI3K/Akt/eNOS pathway; (2) EPC^miR-126 was more effective than EPCs in attenuating infarct volume and NDS and enhancing cMVD, CBF, and angiogenesis; and (3) infusion of EPC^miR-126 increased the number and the level of miR-126 in cEPCs. Our data indicate that miR-126 overexpression enhanced the function of EPCs in vitro and in vivo.

Mobilization of progenitor cells and assessment of vessel healing after second generation drug-eluting stenting by optical coherence tomography

Background

Bone marrow-derived progenitor cells likely contribute to both endothelial- and smooth muscle cell-dependent healing responses in stent-injured vessel sites. This study aimed to assess mobilization of progenitor cells and vessel healing after zotarolimus-eluting (ZES) and everolimus-eluting (EES) stents.

Methods and results

In 63 patients undergoing coronary stent implantation, we measured circulating CD34 + CD133 + CD45low cells and serum levels of biomarkers relevant to stem cell mobilization. In 31 patients of them, we assessed vessel healing within the stented segment using optical coherence tomography (OCT) imaging. The CD34 + CD133 + CD45low cells increased 68 ± 59% 7 days after bare metal stent (BMS), 10 ± 53% after ZES (P < 0.01 vs BMS), 3 ± 49% after EES (P < 0.001 vs BMS), compared with baseline. Percent change in CD34 + CD133 + CD45low cells was positively correlated with that in stromal cell-derived factor (SDF)-1α (R = 0.29, P = 0.034). Percentage of uncovered struts was higher in the EES group (14.4 ± 17.3%), compared with the BMS (0.7 ± 1.3, P < 0.01) and ZES (0.4 ± 0.5, P < 0.01) groups. The change in CD34 + CD133 + CD45low cells showed positive correlation with OCT-quantified mean neointimal area (R = 0.48, P < 0.01). Finally, circulating mononuclear cells obtained from 5 healthy volunteers were isolated to determine the effect of sirolimus, zotarolimus and everolimus on vascular cell differentiation. The differentiation of mononuclear cells into endothelial-like cells was dose-dependently suppressed by sirolimus, zotarolimus, and everolimus.

Conclusions

Mobilization of progenitor cells was suppressed, and differentiation of mononuclear cells into endothelial-like cells was inhibited, in association with increased number of uncovered stent struts, even after second generation drug-eluting stenting. These data suggest that new approaches are necessary to enhance stent healing.

Constitutive Expression of Adiponectin in Endothelial Progenitor Cells Protects a Rat Model of Cerebral Ischemia

Endothelial progenitor cells (EPCs), as precursors to endothelial cells, play a significant part in the process of endogenous blood vessel repair and maintenance of endothelial integrity. Adiponectin (APN) is an adipocyte-specific adipocytokine. In this study, we aim to test whether we transplant a combined graft of EPCs transfected with the adiponectin gene into a rat model of cerebral ischemia could improve functional recovery after middle cerebral artery occlusion (MCAO). Sprague-Dawley (SD) rats were randomly divided into a MCAO control group, a MCAO EPC treatment group, and a MCAO LV-APN-EPC treatment group. A focal cerebral ischemia and reperfusion model was induced by the intraluminal suture method. After 2 h of reperfusion, EPCs were transplanted by injection through the tail vein. A rotarod test was conducted to assess behavioral function before MCAO and on days 1, 7, and 14 after MCAO. After 14 d, TTC staining, CD31 immunofluorescence, and TUNEL staining were used to evaluate infarct volume, microvessel density, and cell apoptosis. Results revealed that behavioral function, infarct area percentage, microvessel density, and cell apoptosis rates were more favorable in the LV-APN-EPC treatment group than in the EPC treatment group. These data suggested that gene-modified cell therapy may be a useful approach for the treatment of ischemic stroke.

Store-operated calcium entry-activated autophagy protects EPC proliferation via the CAMKK2-MTOR pathway in ox-LDL exposure

Improving biological functions of endothelial progenitor cells (EPCs) is beneficial to maintaining endothelium homeostasis and promoting vascular re-endothelialization. Because macroautophagy/autophagy has been documented as a double-edged sword in cell functions, its effects on EPCs remain to be elucidated. This study was designed to explore the role and molecular mechanisms of store-operated calcium entry (SOCE)-activated autophagy in proliferation of EPCs under hypercholesterolemia. We employed oxidized low-density lipoprotein (ox-LDL) to mimic hypercholesterolemia in bone marrow-derived EPCs from rat. Ox-LDL dose-dependently activated autophagy flux, while inhibiting EPC proliferation. Importantly, inhibition of autophagy either by silencing Atg7 or by 3-methyladenine treatment, further aggravated proliferative inhibition by ox-LDL, suggesting the protective effects of autophagy against ox-LDL. Interestingly, ox-LDL increased STIM1 expression and intracellular Ca²⁺ concentration. Either Ca²⁺ chelators or deficiency in STIM1 attenuated ox-LDL-induced autophagy activation, confirming the involvement of SOCE in the process. Furthermore, CAMKK2 (calcium/calmodulin-dependent protein kinase kinase 2, β) activation and MTOR (mechanistic target of rapamycin [serine/threonine kinase]) deactivation were associated with autophagy modulation. Together, our results reveal a novel signaling pathway of SOCE-CAMKK2 in the regulation of autophagy and offer new insights into the important roles of autophagy in maintaining proliferation and promoting the survival capability of EPCs. This may be beneficial to improving EPC transplantation efficacy and enhancing vascular re-endothelialization in patients with hypercholesterolemia.

Endothelial Progenitor Cells Predict Cardiovascular Events after Atherothrombotic Stroke and Acute Myocardial Infarction. A PROCELL Substudy

Introduction

The aim of this study was to determine prognostic factors for the risk of new vascular events during the first 6 months after acute myocardial infarction (AMI) or atherothrombotic stroke (AS). We were interested in the prognostic role of endothelial progenitor cells (EPC) and circulating endothelial cells (CEC)

Methods

Between February 2009 and July 2012, 100 AMI and 50 AS patients were consecutively studied in three Spanish centres. Patients with previously documented coronary artery disease or ischemic strokes were excluded. Samples were collected within 24h of onset of symptoms. EPC and CEC were studied using flow cytometry and categorized by quartiles. Patients were followed for up to 6 months. NVE was defined as new acute coronary syndrome, transient ischemic attack (TIA), stroke, or any hospitalization or death from cardiovascular causes. The variables included in the analysis included: vascular risk factors, carotid intima-media thickness (IMT), atherosclerotic burden and basal EPC and CEC count. Multivariate survival analysis was performed using Cox regression analysis.

Results

During follow-up, 19 patients (12.66%) had a new vascular event (5 strokes; 3 TIAs; 4 AMI; 6 hospitalizations; 1 death). Vascular events were associated with age (P = 0.039), carotid IMT≥0.9 (P = 0.044), and EPC count (P = 0.041) in the univariate analysis. Multivariate Cox regression analysis showed an independent association with EPC in the lowest quartile (HR: 10.33, 95%CI (1.22–87.34), P = 0.032] and IMT≥0.9 [HR: 4.12, 95%CI (1.21–13.95), P = 0.023].

Conclusions

Basal EPC and IMT≥0.9 can predict future vascular events in patients with AMI and AS, but CEC count does not affect cardiovascular risk.

Association between mobilization of circulating endothelial progenitor cells and time or degree of injury from angioplasty in patients with exertional angina: A prospective study

The aim of the present study was to investigate the effect of coronary artery angioplasty on the recruitment of circulating endothelial progenitor cells (EPCs) in patients with angina pectoris. A total of 66 patients treated by coronary stenting were enrolled in the PCI group and 17 patients that underwent angiography alone were enrolled in the control group. The EPC count in the blood was measured by flow cytometry prior to and at 1, 3, 5, 7 and 24 h following angioplasty in the percutaneous coronary intervention (PCI) group, and at three time-points following angiography in the control group. Differences between the two groups included the characteristics of the coronary artery lesions, the incidence of diabetes and family history of coronary heart disease. The mean surface area of the stent deployed was 335.59±234.99 mm². No significant change in EPC count was measured in the control group. In the PCI group, a moderate and delayed increase in the number of cluster of differentiation (CD)34⁺/kinase domain receptor (KDR)⁺ EPCs occurred at 24 h post-balloon inflation compared with the baseline level. The CD133^-/CD34⁺/KDR⁺ subpopulations showed undulating changes at 3, 7 and 24 h post-PCI (P=0.016, P=0.01 and P=0.032, respectively). An arch shape was displayed in CD133⁺/KDR⁺ cells; initially, a reduction occurred at 3 h and was maintained constantly until 7 h (P=0.003, P=0.013 and P=0.033 at 3, 5 and 7 h, respectively), after which a slight increase to the baseline level occurred at 24 h (P=0.084). The CD133⁺/CD34⁺ cells increased in stepwise manner until 24 h. The CD34⁺/KDR⁺ EPC change magnitude correlated significantly with a global damage index by partial correlation analysis (P<0.001). The results suggested that a time-dependent mobilization of EPCs may be initiated by PCI; the change magnitude of the CD34⁺/KDR⁺ cells was associated particularly with endothelial injury degree from the PCI procedure.

Effect of aliskiren on circulating endothelial progenitor cells and vascular function in patients with type 2 diabetes and essential hypertension

BACKGROUND

The aim of this study was to investigate the effects of aliskiren on vascular function and endothelial progenitor cells (EPCs) in patients with type 2 diabetes and essential hypertension.

METHODS

The study enrolled type 2 diabetic patients aged >50 years under stable glycemic control and first diagnosed mild essential hypertension. In phase A (n = 20), patients received aliskiren 150-300 mg daily for 3 months. In phase B (n = 12), hydrochlorothiazide (HCTZ) 12.5-25mg daily substituted for aliskiren for 3 more months. At baseline and at the end of each phase, we assessed (i) brachial blood pressure (BBP); (ii) central aortic systolic pressure (CSP), aortic augmentation index (Aix), and pulse wave velocity (PWV) as markers of arterial stiffness; (iii) brachial artery flow-mediated dilatation (FMD) as a marker of endothelial function; (iv) left ventricular (LV) twisting and untwisting as markers of LV function and (v) EPC numbers in culture of peripheral blood mononuclear cells.

RESULTS

Aliskiren similarly reduced BBP and CSP, increased FMD (P < 0.001) and EPC numbers (P < 0.001), decreased PWV and Aix (P < 0.05), and improved LV twisting and untwisting (P < 0.05). Although substitution of HCTZ sustained BBP at similar levels, CSP and echocardiographic indices nearly returned at baseline levels, and the improvement of FMD, PWV, Aix, and EPC numbers was abolished.

CONCLUSIONS

Aliskiren had a favorable effect on endothelial function and EPCs, reduced arterial stiffness, and improved LV twisting and untwisting. These effects were independent of BBP lowering, as they were not observed after the achievement of similar values of BBP with HCTZ.

Deficiency of the microRNA-31-microRNA-720 pathway in the plasma and endothelial progenitor cells from patients with coronary artery disease

OBJECTIVE

Defects in angiogenesis/vasculogenesis or vessel repair are major complications of coronary artery disease (CAD). Endothelial progenitor cells (EPCs) play a fundamental role in postnatal vascular repair and CAD. The role of microRNAs in CAD pathogenesis and their potential as biomarkers remain to be elucidated.

APPROACH AND RESULTS

MicroRNA-31 (miR-31) level in both the plasma and EPCs of patients with CAD is found lower. miR-31 regulates EPC activities by targeting FAT atypical cadherin 4 and thromboxane A2 receptor, which show increased expression in CAD EPCs. Overexpressing miR-31 in CAD EPCs rescued their angiogenic and vasculogenic abilities both in vitro and in vivo. When exploring approaches to restore endogenous miR-31, we found that far-infrared treatment enhanced the expression of not only miR-31, but also miR-720 in CAD EPCs. miR-720, which was also decreased in EPCs and the plasma of patients with CAD, stimulated EPC activity by targeting vasohibin 1. The miR720-vasohibin 1 pair was shown to be downstream of FAT atypical cadherin 4, but not of thromboxane A2 receptor. FAT atypical cadherin 4 inhibited miR-720 expression via repression of the planar cell polarity signaling gene four-jointed box 1 (FJX1), which was required for miR-720 expression through a hypoxia-inducible factor 1, α subunit-dependent mechanism. Restoring miR-720 level strengthened activity of CAD EPCs. The miR-31-miR-720 pathway is shown critical to EPC activation and that downregulation of this pathway contributes to CAD pathogenesis. Circulating levels of miR-31, miR-720, and vasohibin 1 have the potential to allow early diagnosis of CAD and to act as prognosis biomarkers for CAD and other EPC-related diseases.

CONCLUSIONS

Manipulating the expression of the miR-31-miR-720 pathway in malfunction EPCs should help develop novel therapeutic modalities.

Instruction of circulating endothelial progenitors in vitro towards specialized blood-brain barrier and arterial phenotypes

OBJECTIVE

The vascular system is adapted to specific functions in different tissues and organs. Vascular endothelial cells are important elements of this adaptation, leading to the concept of 'specialized endothelial cells'. The phenotype of these cells is highly dependent on their specific microenvironment and when isolated and cultured, they lose their specific features after few passages, making models using such cells poorly predictive and irreproducible. We propose a new source of specialized endothelial cells based on cord blood circulating endothelial progenitors (EPCs). As prototype examples, we evaluated the capacity of EPCs to acquire properties characteristic of cerebral microvascular endothelial cells (blood-brain barrier (BBB)) or of arterial endothelial cells, in specific inducing culture conditions.

APPROACH AND RESULTS

First, we demonstrated that EPC-derived endothelial cells (EPDCs) co-cultured with astrocytes acquired several BBB phenotypic characteristics, such as restricted paracellular diffusion of hydrophilic solutes and the expression of tight junction proteins. Second, we observed that culture of the same EPDCs in a high concentration of VEGF resulted, through activation of Notch signaling, in an increase of expression of most arterial endothelial markers.

CONCLUSIONS

We have thus demonstrated that in vitro culture of early passage human cord blood EPDCs under specific conditions can induce phenotypic changes towards BBB or arterial phenotypes, indicating that these EPDCs maintain enough plasticity to acquire characteristics of a variety of specialized phenotypes. We propose that this property of EPDCs might be exploited for producing specialized endothelial cells in culture to be used for drug testing and predictive in vitro assays.

Endothelial progenitor cells in cardiovascular diseases: from biomarker to therapeutic agent

Regenerative medicine techniques to recover cardiac and vascular function are being increasingly investigated as management strategies for cardiovascular diseases. Circulating endothelial progenitor cells (EPCs) derived from bone marrow are immature cells capable of differentiating into mature endothelial cells and play a role in vascular reparative processes and neoangiogenesis. The potency of EPCs for cardiovascular regeneration has been demonstrated in many preclinical studies and therapeutic utility of EPCs has been evaluated in early-phase clinical trials. However, the regenerative activity and efficiency of the differentiation of EPCs are still limited, and a directed differentiation method for EPCs cells has not been fully demonstrated. In this review, we introduce the role of circulating EPCs as biomarkers of cardiovascular diseases and medical applications of EPCs for cardiovascular regeneration.

Decreased circulating endothelial progenitor cells as an early risk factor of subclinical atherosclerosis in systemic lupus erythematosus

OBJECTIVE

Endothelial progenitor cells (EPCs) play an important role in vascular damage repair and it has been suggested that a decreased number of these cells is associated with increased subclinical atherosclerosis. Our study aim was to evaluate whether the number of circulating EPCs in patients with SLE is associated with subclinical atherosclerosis, the presence of cardiovascular (CV) risk factors and SLE-specific factors.

METHODS

Forty-six female SLE patients were included. At the time of each patient's appointment, CV risk factors, SLE-specific factors and EPCs were assessed in peripheral blood by flow cytometry. Simultaneously, atherosclerosis was assessed by measuring the carotid-femoral pulse wave velocity (PWV) by Doppler velocimetry, intima media thickness (IMT) and carotid plaque by B-mode US scanning.

RESULTS

Patients were classificated according to PWV following the reference values adjusted by age and blood pressure published by the European Society of Cardiology. Patients with pathological values of PWV showed a significant decrease of circulating EPC percentage compared with normal PWV patients. Decreased EPC counts were also associated with certain risk factors, including hypertension, tobacco use, impaired glucose metabolism, and metabolic syndrome, and correlate with high levels of high-sensitivity CRP (hsCRP) or fibrinogen. The presence of carotid plaque and IMT measurement were unrelated with EPC quantification.

CONCLUSION

Patients with a reduced percentage of EPCs showed pathological arterial stiffness and association with certain CV risk factors, suggesting that the measurement of circulating EPCs can be used as a biological marker to determine subclinical atherosclerosis in SLE.

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.

Toll-like receptor 3 regulates cord blood-derived endothelial cell function in vitro and in vivo

Circulating endothelial progenitor cells (cEPC) are capable of homing to neovascularisation sites, in which they proliferate and differentiate into endothelial cells. Transplantation of cEPC-derived cells, in particular those isolated from umbilical cord blood (UCB), has emerged as a promising approach in the treatment of cardio-vascular diseases. After in vivo transplantation, these cells may be exposed to local or systemic inflammation or pathogens, of which they are a common target. Because Toll-like receptors (TLR) are critical in detecting pathogens and in initiating inflammatory responses, we hypothesized that TLR may govern UCB cEPC-derived cells function. While these cells expressed almost all TLR, we found that only TLR3 dramatically impaired cell properties. TLR3 activation inhibited cell proliferation, modified cell cycle entry, impaired the in vitro angiogenic properties and induced pro-inflammatory cytokines production. The anti-angiogenic effect of TLR3 activation was confirmed in vivo in a hind-limb ischemic mice model. Moreover, TLR3 activation consistently leads to an upregulation of miR-29b, -146a and -155 and to a deregulation of cytoskeleton and cell cycle regulator. Hence, TLR3 activation is likely to be a key regulator of cEPC-derived cells properties.

Endothelial progenitor cells: therapeutic perspective for ischemic stroke

Endothelial progenitor cells (EPCs), which can be cultured in vitro from mononuclear cells in peripheral blood or bone marrow, express both hematopoietic stem cell and endothelial cell markers on their surface. They are believed to participate in endothelial repair and postnatal angiogenesis due to their abilities of differentiating into endothelial cells and secreting protective cytokines and growth factors. Mounting evidence suggests that circulating EPCs are reduced and dysfunctional in various diseases including hypertension, diabetes, coronary heart disease, and ischemic stroke. Therefore, EPCs have been documented to be a potential biomarker for vascular diseases and a hopeful candidate for regenerative medicine. Ischemic stroke, as the major cause of disability and death, still has limited therapeutics based on the approaches of vascular recanalization or neuronal protection. Emerging evidence indicates that transplantation of EPCs is beneficial for the recovery of ischemic cerebral injury. EPC-based therapy could open a new avenue for ischemic cerebrovascular disease. Currently, clinical trials for evaluating EPC transfusion in treating ischemic stroke are underway. In this review, we summarize the general conceptions and the characteristics of EPCs, and highlight the recent research developments on EPCs. More importantly, the rationale, perspectives, and strategies for using them to treat ischemic stroke will be discussed.

Complement system activation and endothelial dysfunction in patients with age-related macular degeneration (AMD): possible relationship between AMD and atherosclerosis

Age-related macular degeneration (AMD) shares several pathological and epidemiological similarities with systemic atherosclerosis (AS). First, an association between AS and AMD is apparent from the analyses of the histological and biochemical structure of atherosclerotic plaques in the vascular walls and retinal drusen, the hallmark of AMD. Second, there is considerable evidence implicating endothelial dysfunction in the pathogenesis of both disorders, and cellular oxidative stress appears to be a common denominator underlying this process. Moreover, there are observations that the complement system (CS) triggering inflammatory response contributes to the onset and advancement of both diseases. The CS plays a role in the generation of drusen and neovascularization in AMD as well as in vascular endothelium activation, cell damage and ultimately atherosclerotic plaque formation in the course of systemic arteriosclerosis. It is widely recognized that both AMD and AS are not only related to local stimulation of the CS, but also result in its systemic activation. In addition, a specific Y402H polymorphism of the complement inhibitor factor H has been found to be associated with the incidence of both AMD and AS. Here, we propose a linking hypothesis between CS activation, endothelial dysfunction and the pathogenesis of two common and age-related pathological processes, AS and AMD. We also discuss the potential therapeutic value of pharmacological modulation of CS activation in these disorders.

Endothelial dysfunction and hypertension in aging

Hypertension is one of the common diseases in the elderly. The prevalence of hypertension markedly increases with advancing age. Both aging and hypertension have a critical role in cardiovascular and cerebrovascular complications. Although aging and hypertension, either independently or collectively, impair endothelial function, aging and hypertension may have similar cascades for the pathogenesis and development of endothelial dysfunction. Nitric oxide (NO) has an important role in regulation of vascular tone. Decrease in NO bioavailability by endothelial dysfunction would lead to elevation of blood pressure. An imbalance of reduced production of NO or increased production of reactive oxygen species, mainly superoxide, may promote endothelial dysfunction. One possible mechanism by which the prevalence of hypertension is increased in relation to aging may be advancing endothelial dysfunction associated with aging through an increase in oxidative stress. In addition, endothelial cell senescence is also involved in aging-related endothelial dysfunction. In this review, we focus on recent findings and interactions between endothelial function, oxidative stress and hypertension in aging.

Genetic module and miRNome trait analyses reflect the distinct biological features of endothelial progenitor cells from different anatomic locations

Background

Endothelial progenitor cells (EPCs) play a fundamental role in post-natal vascular repair, yet EPCs from different anatomic locations possess unique biological properties. The underlying mechanisms are unclear.

Results

EPCs from CB expressed abundant genes involved in cell cycle, hypoxia signalling and blood vessel development, correlating with the phenotypes that CB-EPCs proliferated more rapidly, migrated faster, and formed tubule structure more efficiently. smRNA-seq further deciphered miRNome patterns in EPCs isolated from CB or PB: 54 miRNAs were enriched in CB-EPCs, while another 50 in PB-EPCs. Specifically, CB-EPCs expressed more angiogenic miRNAs such as miR-31, while PB-EPCs possessed more tumor suppressive miRNAs including miR-10a. Knocking down miR-31 levels in CB-EPCs suppressed cell migration and microtubule formation, while overexpressing miR-31 in PB-EPCs helped to recapitulate some of CB-EPC functions.

Conclusions

Our results show the foundation for a more detailed understanding of EPCs from different anatomic sources. Stimulating the expression of angiogenic microRNAs or genes in EPCs of low activity (such as those from patients with cardiovascular diseases) might allow the development of novel therapeutic strategies.

Reversal of endothelial progenitor cell dysfunction in patients with type 2 diabetes using a conditioned medium of human embryonic stem cell-derived endothelial cells

BACKGROUND

The potential clinical application of bone marrow or peripheral blood-derived progenitor cells for cardiovascular regeneration in patients with diabetes mellitus (DM) is limited by their functional impairment. We sought to determine the mechanisms of impaired therapeutic efficacy of peripheral blood-derived progenitor cells in type 2 DM patients and evaluated the use of cell-free conditioned medium obtained from human embryonic stem cell-derived endothelial-like cells (ESC-ECs) to reverse their functional impairment.

METHODS

The angiogenic potential of late outgrowth endothelial cells (OECs) and cytokine profile of the conditional medium of proangiogenic cells (PACs) derived from peripheral blood-mononuclear cells of healthy control and DM patients and ESC-ECs was compared by in vitro tube formation assay and a multiplex bead-based immunoassay kit, respectively. The in vivo angiogenic potential of ESC-ECs derived conditioned medium in rescuing the functional impairment of PB-PACs in DM patients was investigated using a hindlimb ischemia model.

RESULTS

Human ESC-ECs had similar functional and phenotypic characteristics as OECs in healthy controls. Cytokine profiling showed that vascular endothelial growth factor, stromal cell-derived factor 1 and placental growth factor were down-regulated in PACs from DM patients. Tube formation assay that revealed functional impairment of OECs from DM patients could be rescued by ESC-ECs conditioned medium. Administration of ESC-ECs conditioned medium restored the therapeutic efficacy of PB-PACs from DM patients in a mouse model of hindlimb ischemia.

CONCLUSIONS

Our results showed that peripheral blood-derived progenitor cells from DM patients have impaired function because of defective secretion of angiogenic cytokines, which could be restored by supplementation of ESC-ECs conditioned medium.

Menstrual blood transplantation for ischemic stroke: Therapeutic mechanisms and practical issues

Cerebrovascular diseases are a major cause of death and long-term disability in developed countries. Tissue plasmin activator (tPA) is the only approved therapy for ischemic stroke, strongly limited by the short therapeutic window and hemorrhagic complications, therefore excluding most patients from its benefits. The rescue of the penumbra area of the ischemic infarct is decisive for functional recovery after stroke. Inflammation is a key feature in the penumbra area and it plays a dual role, improving injury in early phases but impairing neural survival at later stages. Stem cells can be opportunely used to modulate inflammation, abrogate cell death and, therefore, preserve neural function. We here discuss the possible role of stem cells derived from menstrual blood as restorative treatment for stroke. We highlight the availability, proliferative capacity, pluripotentiality and angiogenic features of these cells and explore their present and future experimental and clinical applications.

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.

Interleukin-18 contributes more closely to the progression of diabetic nephropathy than other diabetic complications

Diabetic complication is comprised of a wide variety of pathophysiological factors involving proinflammatory cytokines, adipokines, and oxidative stress, among others. Each of these complications differs in their incidence and the stage of their occurrence. We examined cytokines and stress markers in 48 patients with type 2 diabetes mellitus and compared the difference of their contribution to pathogenesis between nephropathy and other diabetic complications. Hemoglobin A1c correlated with the level of low-density lipoprotein-cholesterol, and significantly elevated in the severe macroangiopathy group. Cystatin C increased in the severe microangiopathy groups but did not increase in the macroangiopathy group. The levels of interleukin 18 (IL-18), high-sensitive CRP (H-CRP), liver-type fatty acid binding protein, and 8-hydroxy-2-deoxyguanosine increased in the severe microangiopathy group. These data suggest the participation of proinflammatory signaling and oxidative stress in the progression of microangiopathy. In particular, IL-18 and H-CRP were significantly elevated only in the severe nephropathy group but did not significantly elevate in other complications. These data suggest another effect of IL-18 on glomerulus in addition to its proinflammatory effect. In conclusion, we propose that IL18 has a specific role that contributes more closely to the progression of diabetic nephropathy than other diabetic complications.

Endothelial progenitor cells in cardiovascular disease and chronic inflammation: from biomarker to therapeutic agent

The discovery of endothelial progenitor cells in the 1990s challenged the paradigm of angiogenesis by showing that cells derived from hematopoietic stem cells are capable of forming new blood vessels even in the absence of a pre-existing vessel network, a process termed vasculogenesis. Since then, the majority of studies in the field have found a strong association between circulating endothelial progenitor cells and cardiovascular risk. Several studies have also reported that inflammation influences the mobilization and differentiation of endothelial progenitor cells. In this review, we discuss the emerging role of endothelial progenitor cells as biomarkers of cardiovascular disease as well as the interplay between inflammation and endothelial progenitor cell biology. We will also review the challenges in the field of endothelial progenitor cell-based therapy.