Human CD34+/KDR+ cells are generated from circulating CD34+ cells after immobilization on activated platelets

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

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

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.

Biomimetic modification of poly(vinyl alcohol): Encouraging endothelialization and preventing thrombosis with antiplatelet monotherapy

Poly(vinyl alcohol) (PVA) has shown promise as a biomaterial for cardiovascular application. However, its antifouling properties prevent in vivo endothelialization. This work examined the endothelialization and thrombogenicity of modified PVA with different concentrations of proteins and adhesion peptides: collagen, laminin, fibronectin, GFPGER, YIGSR, and cRGD. Material surface properties were quantified, and the endothelialization potential was determined with human endothelial colony forming cells. Additionally, platelet attachment was assessed in vitro with human platelet rich plasma, and promising samples were tested in an ex vivo shunt model. This well-established arteriovenous shunt model was used with and without clinically-relevant antiplatelet therapies, specifically acetylsalicylic acid (ASA) with and without clopidogrel to examine the minimum necessary treatment to prevent thrombosis. Collagen, laminin, and GFPGER biomolecules increased endothelialization, with GFPGER showing the greatest effect at the lowest concentrations. GFPGER-PVA tubes tested under whole blood did exhibit an increase in platelet (but not fibrin) attachment compared to plain PVA and clinical controls. However, application of ASA monotherapy reduced the thrombogenicity of GFPGER-PVA below the clinical control with the ASA. This work is significant in developing cardiovascular biomaterials-increasing endothelialization potential while reducing bleeding side effects by using an antiplatelet monotherapy, typical of clinical patients. STATEMENT OF SIGNIFICANCE: We modified the endothelialization potential of synthetic, hydrogel vascular grafts with proteins and peptides of the vascular tissue matrix. Cell attachment was dramatically increased with the GFPGER peptide, and while some additional platelet attachment was seen under flow with whole blood, this was completely knocked down using clinical antiplatelet monotherapy. This indicates that long-term patency of this biomaterial could be improved without the associated bleeding risk of multiple platelet therapies.

Rapid and selective mobilization of specific stem cell types after consumption of a polyphenol-rich extract from sea buckthorn berries (Hippophae) in healthy human subjects

Purpose

The aim of this study was to evaluate the effects of a proanthocyanidin-rich extract of sea buckthorn berry (SBB-PE) on the numbers of various types of adult stem cells in the blood circulation of healthy human subjects.

Study design and methods

A randomized, double-blind, placebo-controlled, cross-over trial was conducted in 12 healthy subjects. Blood samples were taken immediately before and at 1 and 2 hours after consuming either placebo or 500 mg SBB-PE. Whole blood was used for immunophenotyping and flow cytometry to quantify the numbers of CD45dim CD34+ CD309+ and CD45dim CD34+ CD309− stem cells, CD45− CD31+ CD309+ endothelial stem cells, and CD45− CD90+ mesenchymal stem cells.

Results

Consumption of SBB-PE was associated with a rapid and highly selective mobilization of CD45dim CD34+ CD309− progenitor stem cells, CD45− CD31+ CD309+ endothelial stem cells, and CD45− CD90+ lymphocytoid mesenchymal stem cells. In contrast, only minor effects were seen for CD45dim CD34+ CD309+ pluripotential stem cells.

Conclusion

Consumption of SBB-PE resulted in selective mobilization of stem cell types involved in regenerative and reparative functions. These data may contribute to the understanding of the traditional uses of SBB for preventive health, regenerative health, and postponing the aging process.

Endothelial progenitor cells and rheumatic disease modifying therapy

Rheumatic diseases are associated with accelerated atherosclerosis and with increased risk of cardiovascular morbidity and mortality. The mechanisms underlying the higher prevalence of cardiovascular disease are not completely clarified, but it is likely that a pivotal role is played by vascular inflammation and consequently to altered vascular endothelium homeostasis. Also, high prevalence of traditional risk factors, proatherogenic activation and endothelial dysfunction further contribute to vascular damage. Circulating endothelial progenitor cells (EPCs) can restore dysfunctional endothelium and protect against atherosclerotic vascular disease. However, abnormalities in number and function of these cells in patients with rheumatic condition have been extensively reported. During the last years, growing interest in the mechanisms of endothelial renewal and its potential as a therapy for CVD has been shown; in addition, pioneering studies show that EPC dysfunction might be improved with pharmacological strategies. However, how to restore EPC function, and whether achieving this aim may be effective in preventing cardiovascular complications in rheumatic disease, remain to be established. In this review we report an overview on the current stand of knowledge on the effect of pharmaceutical and lifestyle intervention in improving EPCs number and function in rheumatic disease.

Circulating progenitor cells and their interaction with platelets in patients with an acute coronary syndrome

CD34⁺ cells expressing KDR (CD34⁺/KDR⁺) represent a small proportion of circulating progenitor cells that have the capacity to interact with platelets and to differentiate into mature endothelial cells, thus contributing to vascular homeostasis and regeneration as well as to re-endothelialization. We investigated the levels of CD34⁺ and CD34⁺/KDR⁺ progenitor cells as well as their interaction with platelets in acute coronary syndrome (ACS) patients before the initiation (baseline) of their treatment with a P2Y₁₂ receptor antagonist, and at 5-days post-treatment (follow-up). Sixty-seven consecutive ACS patients and thirty healthy subjects (controls) participated in the study. On admission, all patients received 325 mg aspirin, followed by 100 mg/day and then were loaded either with 600 mg clopidogrel or 180 mg ticagrelor, followed by 75 mg/day (n = 36) or 90 mg × 2/day (n = 31), respectively. The levels of circulating CD34⁺ and CD34⁺/KDR⁺ progenitor cells, as well as their interaction with platelets, were determined by flow cytometry, before and after activation with ADP, in vitro. The circulating levels of CD34⁺ and CD34⁺/KDR⁺ cells in both patient groups at baseline were lower compared with controls while they were significantly increased at 5-days of follow-up in both groups, this increase being more pronounced in the ticagrelor group. The platelet/CD34⁺ (CD61⁺/CD34⁺) conjugates were higher at baseline and reduced at follow-up while the platelet/KDR⁺ (CD61⁺/KDR⁺) conjugates were lower at baseline and increased at follow-up, both changes being more pronounced in the ticagrelor group. ADP activation of control samples significantly increased the KDR expression by CD34⁺ cells and the CD61⁺/KDR⁺ conjugates, these parameters being unaffected in patients at baseline but increased at follow-up. Short-term dual antiplatelet therapy in ACS patients restores the low platelet/KDR⁺ conjugates and CD34⁺ cell levels and improves the low membrane expression levels of KDR in these cells, an effect being more pronounced in ticagrelor-treated patients. This may represent a pleiotropic effect of antiplatelet therapy towards vascular endothelial regeneration.

Role of circulating endothelial progenitor cells in the reparative mechanisms of stable ischemic myocardium

BACKGROUND

Mobilization of endothelial progenitor cells (EPCs) into circulation from bone marrow in patients with acute myocardial infarction has strong scientific evidence; less is known about EPC mobilization in patients with stable coronary artery disease (CAD). The aim of this study was to investigate the association of stable ischemic heart disease with EPC levels in tissue and blood.

METHODS

Fifty-five consecutive patients admitted to a single treatment center for valve or coronary artery bypass grafting (CABG) surgeries were included in the study. Blood samples were collected in the morning before surgery and analyzed by flow-cytometry to determine peripheral EPC levels (EPC/ml). Tissue EPC (CD34+VEGFR2+) levels were assessed on a right atrial appendage segment.

RESULTS

Mean age was 76±5years, 48% were men, and 53% had CAD The number of CD34+ VEGFR2+ cells in the tissue of patients with CAD was significantly higher (p<0.005) and circulating EPC showed a tendency to be reduced by approximately 20% in peripheral blood of patients with CAD when compared to those without CAD.

CONCLUSION

Patients with stable CAD had higher EPC density values (EPC/mm2) and were more likely to have lower EPC blood levels when compare with normal controls.

Circulating progenitor cells in hypertensive subjects: Effectiveness of a treatment with olmesartan in improving cell number and miR profile in addition to expected pharmacological effects

CD34+ circulating progenitor cells (CD34+CPCs) are a population of multipotent cells which can delay the development of atherosclerosis and cardiovascular disease (CVD) in conditions of increased CV risk. MicroRNAs (miRs) 221 and 222 modulate different genes regulating angiogenesis and inflammation; moreover, miR221/22 have beenshown to participate in differentiation and proliferation of CD34+CPCs, inhibiting cell migration and homing. miR221/222 in CD34+CPCs from hypertensive subjects are also increased and associated with CD34+cell number and reactive oxygen species (ROS). We evaluated CD34+CPC number, intracellular miR221/222 and ROS levels, arterial stiffness (AS)and echocardiography indices at baseline (T0).Then, after a six-month treatment with olmesartan, 20 mg/day (T1), in 57 hypertensive patients with left ventricular hypertrophy (LVH) and with no additional risk factor for CVD, and in 29 healthy controls (baseline),fibrinogen, C-reactive protein (CRP), glucose and lipid profiles were also evaluated.At T1, blood pressure values, CRP and fibrinogen levels, ROS and miR221/222 were significantly decreased (all p <0.001), as were AS indices and LV mass index (p<0.001), while cell number was increased (p<0.001). Olmesartan is effective in reducing miR and ROS levels in CD34+CPCs from hypertensive subjects, as well as in increasing CD34+CPC number, providing multilevel CV protection, in addition to its expected pharmacological effects.

Traditional cardiovascular risk factors or inflammation: Which factors accelerate atherosclerosis in arthritis patients?

Patients with chronic inflammatory arthritis experience an increased incidence of cardiovascular (CV) events. In addition to visualizing atherosclerotic plaques, ultrasound examinations (USs) of the carotid arteries permit the measurement of subclinical markers of atherosclerosis, such as intima-media thickness (cIMT) and carotid segmental distensibility (cDC). The aims of the study were to identify the determinants of atherosclerosis acceleration (plaques, cIMT and cDC) in a sample of patients suffering from chronic arthritis and to compare these patients with a control group of people with ≤1 traditional risk factor (TRF) for CV disease.

METHODS

We recruited 137 patients with rheumatoid arthritis (RA), 43 patients with psoriatic arthritis (PsA), 28 patients with ankylosing spondylitis (AS) and 48 healthy volunteers without histories of previous CV events. These patients underwent carotid artery US examinations using dedicated hardware.

RESULTS

Regression and multivariate analyses demonstrated that only age (p<0.001) was consistently associated with cDC, cIMT and atherosclerotic plaques, both in the entire sample of patients with arthritis and in the subgroup of patients with RA. Among modifiable TRFs for cardiovascular disease, only hypertension, diabetes mellitus and smoking exhibited associations with some carotid phenotypes, with borderline significance. When patients with RA carrying ≤1 TRF were compared with control subjects carrying ≤1 TRF, only cDC was slightly lower in the RA group than in the control group.

CONCLUSIONS

Age is the major determinant of subclinical atherosclerosis in patients with different types of arthritis, as the contributions of other TRFs and disease activity and duration indices to the disease seem to be limited.

In situ tissue engineering: endothelial growth patterns as a function of flow diverter design

Background

Vascular remodeling in response to implantation of a tissue engineering scaffold such as a flow diverter (FD) leads to the cure of intracranial aneurysms. We hypothesize that the vascular response is dependent on FD design, and CD34+ progenitor cells play an important role in the endothelialization of the implant.

Methods

Sixteen rabbit aneurysms were randomly treated with two different single-layer braided FDs made of cobalt–chrome alloys. The FD-48 and FD-72 devices had 48 and 72 wires, respectively. Aneurysm occlusion rate was assessed during the final digital subtraction angiogram at 10, 20, 30, and 60 days (n=2 per device per time point). Implanted vessels were analyzed with scanning electron microscopy for tissue coverage, endothelialization, and immuno-gold labeling for CD34+ cells.

Results

Complete aneurysm occlusion rates were similar between the devices; however, complete or near complete occlusion was more frequently observed in aneurysms with neck ≤4.2 mm (p=0.008). Total tissue coverage at 10 days over the surface of the FD-48 and FD-72 devices was 56.4±11.6% and 76.6±3.6%, respectively. Endothelial cell growth over the surface was time-dependent for the FD-72 device (Spearman's r=0.86, p=0.013) but not for the FD-48 device (Spearman's r=−0.59, p=0.094). The endothelialization score was marginally correlated with the distance from the aneurysm neck for the FD-48 device (Spearman's r=1, p=0.083) but not for the FD-72 device (Spearman's r=0.8, p=0.33). CD34+ cells were present along the entirety of both devices at all time points.

Conclusions

This study gives preliminary evidence that temporal and spatial endothelialization is dependent on FD design. Circulating CD34+ progenitor cells contribute to endothelialization throughout the healing process.

Endothelial Progenitor Cells for Diagnosis and Prognosis in Cardiovascular Disease

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

Stimulating endogenous cardiac repair

The healthy adult heart has a low turnover of cardiac myocytes. The renewal capacity, however, is augmented after cardiac injury. Participants in cardiac regeneration include cardiac myocytes themselves, cardiac progenitor cells, and peripheral stem cells, particularly from the bone marrow compartment. Cardiac progenitor cells and bone marrow stem cells are augmented after cardiac injury, migrate to the myocardium, and support regeneration. Depletion studies of these populations have demonstrated their necessary role in cardiac repair. However, the potential of these cells to completely regenerate the heart is limited. Efforts are now being focused on ways to augment these natural pathways to improve cardiac healing, primarily after ischemic injury but in other cardiac pathologies as well. Cell and gene therapy or pharmacological interventions are proposed mechanisms. Cell therapy has demonstrated modest results and has passed into clinical trials. However, the beneficial effects of cell therapy have primarily been their ability to produce paracrine effects on the cardiac tissue and recruit endogenous stem cell populations as opposed to direct cardiac regeneration. Gene therapy efforts have focused on prolonging or reactivating natural signaling pathways. Positive results have been demonstrated to activate the endogenous stem cell populations and are currently being tested in clinical trials. A potential new avenue may be to refine pharmacological treatments that are currently in place in the clinic. Evidence is mounting that drugs such as statins or beta blockers may alter endogenous stem cell activity. Understanding the effects of these drugs on stem cell repair while keeping in mind their primary function may strike a balance in myocardial healing. To maximize endogenous cardiac regeneration, a combination of these approaches could ameliorate the overall repair process to incorporate the participation of multiple cellular players.

Vitamin D Status in Rheumatoid Arthritis: Inflammation, Arterial Stiffness and Circulating Progenitor Cell Number

Background and Aims

Suboptimal vitamin D status was recently acknowledged as an independent predictor of cardiovascular diseases and all-cause mortality in several clinical settings, and its serum levels are commonly reduced in Rheumatoid Arthritis (RA). Patients affected by RA present accelerated atherosclerosis and increased cardiovascular morbidity and mortality with respect to the general population. In RA, it has been reported an impairment of the number and the activity of circulating proangiogenic haematopoietic cells (PHCs), including CD34+, that may play a role in endothelial homeostasis. The purpose of the study is to investigate the association between vitamin D levels and PHCs, inflammatory markers, and arterial stiffening in patients with RA.

Methods and Results

CD34+ cells were isolated from 27 RA patients and 41 controls. Vitamin D levels, C-reactive protein (CRP), fibrinogen, pulse wave velocity (PWV), and carotid intima-media thickness (cIMT) were also evaluated. CD34+ count and vitamin D levels were lower in RA patients as compared to controls, while fibrinogen, CRP, PWV and cIMT were higher in RA patients. CD34+ cell number appeared to be associated with vitamin D levels, and negatively correlated to fibrinogen and early atherosclerosis markers (PWV and cIMT); vitamin D levels appear also to be inversely associated to fibrinogen.

Conclusions

RA patients with moderate disease activity presented with low vitamin D levels, low CD34+ cell count, increased PWV and cIMT; we found that vitamin D deficiency is associated to CD34+ cell reduction in peripheral blood, and with fibrinogen levels. This suggests that vitamin D might contribute to endothelial homeostasis in patients with RA.

Endothelial Repair in Childhood Arterial Ischaemic Stroke with Cerebral Arteriopathy

Background

We have previously shown that recurrent arterial ischaemic stroke (AIS) in children with cerebral arteriopathy is associated with increased circulating endothelial cells and endothelial microparticles, consistent with ongoing endothelial injury. To date, however, little is known about endothelial repair responses in childhood AIS. We examined the relationship between the number and function of circulating endothelial progenitor cells (EPC), the levels of brain-derived neurotrophic factor (BDNF) and AIS recurrence.

Methods

Flow cytometry was used to identify peripheral blood mononuclear cells positive for CD34/kinase insert domain-containing receptor (KDR). In a subgroup of patients (5 in each group selected at random), monocytic EPC function was assessed by colony-forming unit (EPC-CFU) capacity and incorporation into endothelial cell networks in Matrigel. BDNF was measured using ELISA.

Results

Thirty-five children, aged 12 years (range: 5-16.5; 9 males), with AIS and cerebral arteriopathy were studied; 10 had recurrent AIS. CD34+/KDR+ cells were significantly higher in recurrent AIS compared to non-recurrent AIS patients (p = 0.005) and controls (p = 0.0002). EPC-CFU and EPC incorporation into endothelial cell networks were significantly reduced in recurrent compared to non-recurrent AIS patients (p = 0.04 and p = 0.01, respectively). Levels of BDNF were significantly higher in recurrent compared to non-recurrent AIS patients (p = 0.0008) and controls (p = 0.0002).

Conclusions

Children with recurrent AIS and cerebral arteriopathy had increased circulating CD34+/KDR+ cells and BDNF consistent with an endothelial repair response. However, EPC function was impaired. Future studies are needed to examine whether suboptimal endothelial repair contributes to childhood AIS recurrence.

Cross talk with hematopoietic cells regulates the endothelial progenitor cell differentiation of CD34 positive cells

INTRODUCTION

Despite the crucial role of endothelial progenitor cells (EPCs) in vascular regeneration, the specific interactions between EPCs and hematopoietic cells remain unclear.

METHODS

In EPC colony forming assays, we first demonstrated that the formation of EPC colonies was drastically increased in the coculture of CD34+ and CD34- cells, and determined the optimal concentrations of CD34+ cells and CD34- cells for spindle-shaped EPC differentiation.

RESULTS

Functionally, the coculture of CD34+ and CD34- cells resulted in a significant enhancement of adhesion, tube formation, and migration capacity compared with culture of CD34+ cells alone. Furthermore, blood flow recovery and capillary formation were remarkably increased by the coculture of CD34+ and CD34- cells in a murine hind-limb ischemia model. To elucidate further the role of hematopoietic cells in EPC differentiation, we isolated different populations of hematopoietic cells. T lymphocytes (CD3+) markedly accelerated the early EPC status of CD34+ cells, while macrophages (CD11b+) or megakaryocytes (CD41+) specifically promoted large EPC colonies.

CONCLUSION

Our results suggest that specific populations of hematopoietic cells play a role in the EPC differentiation of CD34+ cells, a finding that may aid in the development of a novel cell therapy strategy to overcome the quantitative and qualitative limitations of EPC therapy.

Circulating progenitor cells in hypertensive patients with different degrees of cardiovascular involvement

We investigated whether different degrees of hypertension-related cardiovascular involvement are associated with changes in circulating proangiogenic hematopoietic cell (PHC) numbers and/or phenotypes and/or in the PHC redox system in hypertensive individuals with isolated arterial stiffening (AS) hypertensives or with both carotid intima-media thickening and left ventricular hypertrophy (LVH) hypertensives. We also evaluated microRNA (miRs) 221 and 222 (miRs221/222) expression in CD34+ cells, the relationship between these miRs and cell number and reactive oxygen species (ROS) levels, and the expression of manganese superoxide dismutase (MnSOD), catalase (CAT) glutathione peroxidase type-1 (GPx-1) and gp91phox-containing nicotinamide-adenine-dinucleotide-phosphate-oxidase (NOX2). Proangiogenic hematopoietic cells (PHCs) from hypertensive patients and controls were isolated by flow cytometry. PHCs were higher in hypertensives than in controls but were lower in LVH than in AS hypertensives. In CD34+ cells from AS hypertensives, NOX2, MnSOD, CAT and GPx-1 were overexpressed; ROS, miRs and NOX2 were also increased and were associated with cell number. In LVH, we found an imbalance in the cell redox system; MnSOD showed the highest values, whereas CAT and GPx-1 were lower than in AS hypertensives. Intracellular ROS, miRs and NOX2 were higher and inversely associated with cell number. In AS hypertensives, the redox balance may sustain the increase in PHCs; by contrast, in hypertensives with more advanced lesions, redox imbalance may result in increased oxidative stress and cell reduction.

Circulating progenitor cells in rheumatoid arthritis: association with inflammation and oxidative stress

OBJECTIVES

To evaluate the association between inflammation, oxidative stress, and circulating progenitor cell (CPC) number and redox equilibrium, vascular lesions and accelerated atherosclerosis in rheumatoid arthritis (RA).

METHOD

Circulating CD34+ cells were isolated from 33 RA patients and 33 controls. Reactive oxygen species (ROS) levels and mRNA expression of manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase type 1 (GPx-1) antioxidant enzymes, and the gp91phox-containing nicotinamide adenine dinucleotide phosphate (NADPH) oxidase NOX2 were measured in CD34+ cells. C-reactive protein (CRP), fibrinogen, erythrocyte sedimentation rate (ESR), carotid intima-media thickness (cIMT), and arterial stiffness (AS) were also evaluated. We investigated the relationships between inflammatory markers, vascular parameters, cell number, and antioxidant enzymes.

RESULTS

CD34+ cell number was lower in RA patients than in controls. In CD34+ cells from RA patients, ROS levels, MnSOD mRNA, and NOX2 mRNA were higher, while mRNA expression of GPx-1 and CAT was significantly lower. The AS, pulse wave velocity (PWV), and augmentation index (AIx) were higher, as was cIMT. CD34+ cell number was inversely correlated with CRP, ROS, PWV, and AIx, and with the CAT/MnSOD and GPx-1/MnSOD ratios. CRP was correlated with MnSOD mRNA, PWV, and AIx but not with CAT and GPx-1 mRNA.

CONCLUSIONS

Our data show a link between inflammation, oxidative stress, and the impairment of the antioxidant system of CPCs and their number, and with arterial stiffness in RA subjects. This could suggest a perspective on the accelerated development of vascular damage and atherosclerosis in RA.

Circulating and tissue resident endothelial progenitor cells

Progenitor cells for the endothelial lineage have been widely investigated for more than a decade, but continue to be controversial since no unique identifying marker has yet been identified. This review will begin with a discussion of the basic tenets originally proposed for proof that a cell displays properties of an endothelial progenitor cell. We then provide an overview of the methods for putative endothelial progenitor cell derivation, expansion, and enumeration. This discussion includes consideration of cells that are present in the circulation as well as cells resident in the vascular endothelial intima. Finally, we provide some suggested changes in nomenclature that would greatly clarify and demystify the cellular elements involved in vascular repair.

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

BACKGROUND

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

OBJECTIVES

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

METHODS/RESULTS

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

CONCLUSIONS

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

Aspirin treatment hampers the use of plasma microRNA-126 as a biomarker for the progression of vascular disease

AIMS

MicroRNA-126 (miR-126) facilitates angiogenesis and regulates endothelial cell function. Recent data suggest that miR-126 can serve as a biomarker for vascular disease. Although endothelial cells are enriched for miR-126, platelets also contain miR-126. In this paper, we investigated the contribution of platelets to the pool of miR-126 in plasma of patients with type 2 diabetes (DM2) and how this is affected by aspirin.

METHODS AND RESULTS

In vitro platelet activation resulted in the transfer of miR-126 from the platelet to the plasma compartment, which was prevented by aspirin. In vivo platelet activation, monitored in patients with DM2 by measuring soluble P-selectin, correlated directly with circulating levels of miR-126. The administration of aspirin resulted both in platelet inhibition and concomitantly reduced circulating levels of platelet-derived microRNAs including miR-126.

CONCLUSION

Platelets are a major source of circulating miR-126. Consequently, in patho-physiological conditions associated with platelet activation, such as diabetes type 2, the administration of aspirin may lead to reduced levels of circulating miR-126. Thus, the use of platelet inhibitors should be taken into account when using plasma levels of miR-126 as a biomarker.

Analysis of endothelial precursor cells in chronic migraine: a case-control study

BACKGROUND

Migraine has been considered a vascular risk factor especially in young women. Factors predisposing to endothelial damage in migraine are still being debated. The insufficiency of circulating endothelial precursor circulating cells (EPCs) suggested a link between migraine and cardiovascular risk. This research aimed to study a subtype of EPCs, those expressing e-selectin, to assess endothelial activation and, therefore, endothelial dysfunction in migraine.

METHODS

Consecutive headache patients (n = 99) and 35 adjusted controls were recruited. Total EPCs, defined as CD34+/KDR+ cells, and EPC colony-forming units (CFUs) were assayed. We identified as "early" EPCs those CD62E- EPCs, and "late" EPCs, CD62E+, a surrogate marker for endothelial damage. Plasmatic calcitonin-gene related protein (CGRP) and vascular-endothelial growth factor (VEGF) were analyzed.

RESULTS

We did not find differences in the total number of CFUs among clinical groups. Means of total CD34+/KDR+ and "early" EPCs were not significant among clinical groups. Nevertheless, the mean of "late" EPCs was lower (log(10)-transformed mean = 1.715; SD = 0.393) in the control group than in the migraine patients (log(10)-transformed mean = 2.167; SD = 0.685), even after adjustment by VEGF plasma level and other confounding factors. Linear regression analyses disclosed significant predictors for "late" EPCs for controls vs migraine (β = 0.452 SE ± 0.13; p = 0.001). We did not observe differences between migraine with or without aura.

CONCLUSION

We observed higher number of activated EPCs in migraine patients than in controls. CD62E+ EPCs might be considered a marker for vascular damage in migraine patients.

Circulating progenitor cells and the elderly: a seven-year observational study

Cardiovascular (CV) diseases and related complications are the main causes of morbidity and mortality in the elderly. CV progenitor cells, including CD34+ cells, play a role in delaying the progression of atherosclerosis. In the present study we observed 100 octogenarians for seven years, in order to address the question of whether CD34+ cell number is a predictor of longevity in selected survivors. We also checked for associations of cell expression of manganese superoxide dismutase (Mn-SOD), catalase (CAT), and glutathione peroxidase type-1 (GPx-1) antioxidative enzymes, with number of CD34+ progenitor cells and mortality. We found that in very old subjects the number of CD34+ cells at baseline were higher in subjects who reached older age at death or were still living at the end of observation period, with respect to subjects who died from all causes, including CV deaths. On the other hand, HDL-C plasma levels and, with the exception of diabetes, the classic CV risk factors (hypertension, smoking, hypercholesterolemia) showed a loss of their predictive power. A significant association between the redox system of CD34+ cells and mortality was also observed. These data suggest that, even in the elderly, CD34+ cells maintain their role in predicting mortality. CD34+ cells could thus be considered as a biomarker of longevity.

1-year outcome of TRIAS HR (TRI-stent adjudication study-high risk of restenosis) a multicenter, randomized trial comparing genous endothelial progenitor cell capturing stents with drug-eluting stents

OBJECTIVES

This study sought to demonstrate the noninferiority of endothelial progenitor cell capturing stents (ECS) relative to drug-eluting stents (DES) regarding target lesion failure (TLF) and the composite of cardiac death, myocardial infarction, and target lesion repeat revascularization within 1 year.

BACKGROUND

A "pro-healing" approach for prevention of in-stent restenosis is theoretically favorable over the use of cytotoxic/cytostatic drugs released from DES to treat coronary artery disease. Promoting accelerated endothelialization of the stent, ECS have shown promising results in studies with patients carrying noncomplex lesions.

METHODS

We undertook an international, clinical trial in 26 centers planning to randomize 1,300 patients with stable coronary artery disease and with a high risk of restenosis between treatment, with either ECS or DES. After a routine review with 50% of the patients enrolled, early cessation of the trial was recommended by the data and safety monitoring board when TLF in the ECS population was higher and treatment of new patients with an ECS would be unreasonable.

RESULTS

At 1 year evaluating 304 patients receiving ECS and 318 receiving DES, TLF occurred in 17.4% of the ECS-treated patients and in 7.0% of the DES-treated patients (p = 0.98 for noninferiority).

CONCLUSIONS

Within 1 year, inhibition of intimal hyperplasia by the ECS is not sufficiently strong to compete with DES in terms of restenosis prevention in patients/lesions with a high risk of restenosis. Furthermore, long-term follow-up is pivotal to fully appreciate the clinical value of ECS, including the effect on late intimal hyperplasia regression.

Endothelial colony-forming cells show a mature transcriptional response to shear stress

Endothelial progenitor cells (EPC) play a central role in endothelial maintenance and repair. Endothelial colony-forming cells (ECFC) form a subpopulation of EPC. ECFC are readily attainable, can be easily isolated, possess a high proliferation potential, and are therefore a promising source of endothelial cells (EC) for future cardiovascular therapeutic applications. The extent to which these cells respond to shear stress as adult vascular EC remains to be elucidated. Here, we study the transcriptional response of ECFC induced by shear stress and compare it with the response of mature arterial and venous cells. ECFC, as well as human umbilical vein EC (HUVEC) and human umbilical artery EC (HUAEC), were subjected to low (0.5 Pa) and high (2.5 Pa) shear stress. The endothelial differentiation phenotype and transcriptional responses were analyzed using immunocytochemistry and quantitative polymerase chain reaction (Q-PCR). Performing absolute quantification of copy numbers by Q-PCR allows comparing the responses of cell types relative to each other. Our data show that isolated ECFC resemble mature EC in cobblestone morphology and endothelial marker expression. Absolute Q-PCR quantification revealed that although being truly endothelial, ECFC do not fully resemble HUVEC or HUAEC in the expression of specific differentiation markers. When subjected to shear stress, ECFC show a mature response to fluid flow, comparable to that of HUVEC and HUAEC. The capacity of endothelial progenitors to respond to fluid flow in a similar manner to HUVEC and HUAEC highlights the universal response of EC to fluid shear stress, independently of their endothelial differentiation status. This property supports the use of these cells as an EC source for tissue engineering applications.

MicroRNA-126 modulates endothelial SDF-1 expression and mobilization of Sca-1(+)/Lin(-) progenitor cells in ischaemia

AIMS

MicroRNA-126 (miR-126), which is enriched in endothelial cells, plays a role in angiogenesis. Based on the seed sequence, miR-126 can also be predicted to regulate vasculogenesis by modulating the endothelial expression of stromal cell-derived factor-1 (SDF-1).

METHODS AND RESULTS

Using miR-reporter constructs, we first validated that miR-126 inhibits SDF-1 expression in endothelial cells in vitro. Next, we investigated the potential relevance of this observation with respect to the mobilization of progenitor cells. For this, we studied the migration of human CD34+ progenitor cells towards chemotactic factors present in endothelial cell-conditioned medium. Antagomir-induced silencing of miR-126 elevated SDF-1 expression by human umbilical vein endothelial cells and enhanced migration of the CD34+ cells. In a murine model of hind limb ischaemia, a striking increase in the number of circulating Sca-1(+)/Lin(-) progenitor cells in antagomir-126-treated mice was observed when compared with scramblemir-treated controls. Immunohistochemical staining of capillaries in the post-ischaemic gastrocnemius muscle of miR-126-silenced mice revealed elevated SDF-1 expressing CD31-positive capillaries, whereas a mobilizing effect of miR-126 inhibition was not detected in healthy control animals.

CONCLUSION

miR-126 can regulate the expression of SDF-1 in endothelial cells. In the context of an ischaemic event, systemic silencing of miR-126 leads to the mobilization of Sca-1(+)/Lin(-) progenitor cells into the peripheral circulation, potentially in response to elevated SDF-1 expression by endothelial cells present in the ischaemic tissue.

Circulating progenitor cells are increased in newly diagnosed untreated hypertensive patients with arterial stiffening but normal carotid intima-media thickness

Circulating progenitor cells (CPCs), including endothelial progenitor cells (EPCs), have a key role in endothelium repair. Cellular NADPH oxidase (Nox) enzymes, including Nox-containing gp91phox, represent a source of reactive oxygen species (ROS); ROS trigger protective signals but may also have detrimental effects. Cellular defenses against ROS include the enzymes manganese superoxide dismutase (MnSOD), catalase (CAT) and glutathione peroxidase type-1 (GPx-1). We investigated the relationships of CPCs with cellular gp91phox, MnSOD, CAT, GPx-1 and ROS levels and with carotid intima-media thickness (cIMT) and stiffness in hypertensives without additional risk factors for cardiovascular disease. CPCs from 53 newly diagnosed, untreated hypertensives and from 29 controls were isolated and identified by flow cytometry. gp91phox, MnSOD, CAT, and GPx-1 mRNA and protein expression and ROS generation were evaluated in enriched samples of CD34(+) cells; cIMT and stiffness were assessed. Hypertensives showed higher arterial stiffness (P < 0.001) but no difference in cIMT with respect to controls. ROS generation was slightly increased (P=0.04), whereas gp91phox, MnSOD, CAT and GPx-1 were significantly higher (P < 0.001) with respect to controls, as was CPC number (P < 0.001), but EPCs were no different. CPC and EPC numbers correlated with gp91phox, ROS and fibrinogen (P < 0.001); moreover, gp91phox, MnSOD, CAT and GPx-1 were correlated with CPC number. In early phases of arterial hypertension, before the development of wall thickening and even in the presence of arterial mechanical impairment, CPC number may be increased to maintain an adequate number of EPCs in peripheral blood.