Circulating Endothelial Progenitor Cells and Clinical Outcome in Patients with Aortic Stenosis

Circulating progenitor cells and outcomes in patients with coronary artery disease

BACKGROUND

Low quantities of circulating progenitor cells (CPCs), specifically CD34+ populations, reflect impairment of intrinsic regenerative capacity. This study investigates the relationship between subsets of CPCs and adverse outcomes.

METHODS

1366 individuals undergoing angiography for evaluation of coronary artery disease (CAD) were enrolled into the Emory Cardiovascular Biobank. Flow cytometry identified CPCs as CD45med blood mononuclear cells expressing the CD34 epitope, with further enumeration of hematopoietic CPCs as CD133+/CXCR4+ cells and endothelial CPCs as vascular endothelial growth factor receptor-2 (VEGFR2+) cells. Adjusted Cox or Fine and Gray's sub-distribution hazard regression models analyzed the relationship between CPCs and 1) all-cause death and 2) a composite of cardiovascular death and non-fatal myocardial infarction (MI).

RESULTS

Over a median 3.1-year follow-up period (IQR 1.3-4.9), there were 221 (16.6%) all-cause deaths and 172 (12.9%) cardiovascular deaths/MIs. Hematopoietic CPCs were highly correlated, and the CD34+/CXCR4+ subset was the best independent predictor. Lower counts (≤median) of CD34+/CXCR4+ and CD34+/VEGFR2+ cells independently predicted all-cause mortality (HR 1.46 [95% CI 1.06-2.01], p = 0.02 and 1.59 [95% CI 1.15-2.18], p = 0.004) and cardiovascular death/MI (HR 1.50 [95% CI 1.04-2.17], p = 0.03 and 1.47 [95% CI 1.01-2.03], p = 0.04). A combination of low CD34+/CXCR4+ and CD34+/VEGFR2+ CPCs predicted all-cause death (HR 2.1, 95% CI 1.4-3.0; p = 0.0002) and cardiovascular death/MI (HR 2.0, 95% CI 1.3-3.2; p = 0.002) compared to those with both lineages above the cut-offs.

CONCLUSIONS

Lower levels of hematopoietic and endothelial CPCs indicate diminished endogenous regenerative capacity and independently correlate with greater mortality and cardiovascular risk in patients with CAD.

Pleiotropic effect of erythropoiesis-stimulating agents on circulating endothelial progenitor cells in dialysis patients

BACKGROUND

Recent studies have suggested that erythropoiesis-stimulating agents (ESAs) may accelerate not only angiogenesis but also vasculogenesis, beyond erythropoiesis.

METHODS

We conducted a 12-week prospective study in 51 dialysis patients; 13 were treated with recombinant human erythropoietin (EPO, 5290.4 ± 586.9 IU/week), 16 with darbepoetin (DA, 42.9 ± 4.3 µg/week), 12 with epoetin β pegol (CERA, 40.5 ± 4.1 µg/week) and 10 with no ESAs. Vascular mediators comprising endothelial progenitor cells (EPCs), vascular endothelial growth factor (VEGF), matrix metalloproteinase-2 (MMP-2), and high-sensitivity C-reactive protein (hs-CRP) were measured at 0 and 12 weeks. EPCs were measured by flow cytometry as CD45^lowCD34⁺CD133⁺ cells.

RESULTS

The EPC count increased significantly to a greater extent in the EPO group than in the other three group, and increased significantly from 0 to 12 weeks in a EPO dose-dependent manner. In both the DA and CERA groups, the EPC count did not change at 12 weeks. Serum levels of VEGF, MMP-2 and hs-CRP were not affected by ESA treatment in all groups. In the CERA group, serum ferritin decreased significantly compared to the no-ESA group and correlated with CERA dose, although use of iron was permitted if required during the prospective study period of 12 weeks.

CONCLUSIONS

When patients on dialysis were treated with clinical doses of various ESAs, only EPO induced a significant increase of circulating EPCs from bone marrow, whereas, DA and CERA had no effect.

Assessment of endothelial progenitor cells, VEGF-A and SDF-1α in Hodgkin's lymphoma

Recently, there is great interest in vasculogenesis, a process of the formation of new blood vessels from progenitor cells or angioblasts, in the pathogenesis of cancer. To the best of our knowledge, the evaluation of endothelial progenitor cells (EPCs) in Hodgkin's lymphoma has not yet been reported. The aim of the present study was to assess the number of EPCs and selected cytokines, such as vascular endothelial growth factor (VEGF-A) and stromal cell-derived factor (SDF-1α) involved in vasculogenesis in Hodgkin's lymphoma patients. The study was conducted in a group of 42 patients with Hodgkin's lymphoma (eight patients with relapsed Hodgkin's lymphoma and 34 patients before the first treatment) and 30 healthy controls. The number of EPCs defined as CD31(+), CD34(+), CD45(-), CD133(+) was analysed on FacsCalibur flow cytometer and the concentration of VEGF-A and SDF-1α was assessed by ELISA. The study showed that there was a significantly higher EPCs number and VEGF-A concentration in the blood of Hodgkin's lymphoma patients compared to healthy individuals (8.20 vs. 0.55 cells/μl; P < 0.000001; 85.10 vs. 25.33 pg/ml, P = 0.000017; respectively). Detailed analysis revealed that there was elevated EPCs number in both study subgroups as compared to the control group. However, there was no difference in VEGF concentration between recurrent Hodgkin's lymphoma patients and the control group. A significant positive correlation was found between the number of EPCs and VEGF-A concentration (R = 0.31, P = 0.047). Significantly higher EPCs number combined with increased VEGF-A concentration, found in Hodgkin's lymphoma patients before the first treatment, suggest stimulation of new blood vessels formation, which may in turn contribute to tumour growth and metastasis in these patients.

Reduced Number and Activity of Circulating Endothelial Progenitor Cells in Acute Aortic Dissection and Its Relationship With IL-6 and IL-17

This study investigates the alteration in function and number of circulating endothelial progenitor cells (EPCs) in patients with aortic dissection (AD), compared with hypertensive patients, and its possible mechanism. Thirty-four patients with acute aortic dissection (AAD) and 20 patients with primary hypertension were involved. Flow cytometry analysis was performed to detect the number of CD34+/KDR+ cells, and acetylated low density lipoprotein (ac-LDL) and lectin fluorescent staining method was applied to test the number of cultured EPCs. In addition, EPC migration and proliferation were measured, and plasma interleukin 6 (IL-6) and interleukin 17 (IL-17) levels were investigated. The number of circulating EPCs in the AAD group was lower than that in the non-AD group, and the proliferation and migration of circulating EPCs in the AAD group were lower than that in the non-AD group. In addition, the number, proliferation, and migration of circulating EPCs were significantly inversely correlated with the aortic dissection detection risk score (ADD-RS). More importantly, increased plasma IL-6 and IL-17 level was found in the AAD group, and the two inflammatory factors were inversely associated with the function and number of circulating EPCs in the AAD group. We first demonstrated that the number and function of circulating EPCs are reduced in the AAD group, which may be partly related to upregulated plasma IL-6 and IL-17. Our study provides novel insight on the underlying mechanism and potential therapeutic target of AAD.

Circulating stem cells and cardiovascular outcomes: from basic science to the clinic

The cardiovascular and haematopoietic systems have fundamental inter-relationships during development, as well as in health and disease of the adult organism. Although haematopoietic stem cells (HSCs) emerge from a specialized haemogenic endothelium in the embryo, persistence of haemangioblasts in adulthood is debated. Rather, the vast majority of circulating stem cells (CSCs) is composed of bone marrow-derived HSCs and the downstream haematopoietic stem/progenitors (HSPCs). A fraction of these cells, known as endothelial progenitor cells (EPCs), has endothelial specification and vascular tropism. In general, the levels of HSCs, HSPCs, and EPCs are considered indicative of the endogenous regenerative capacity of the organism as a whole and, particularly, of the cardiovascular system. In the last two decades, the research on CSCs has focused on their physiologic role in tissue/organ homoeostasis, their potential application in cell therapies, and their use as clinical biomarkers. In this review, we provide background information on the biology of CSCs and discuss in detail the clinical implications of changing CSC levels in patients with cardiovascular risk factors or established cardiovascular disease. Of particular interest is the mounting evidence available in the literature on the close relationships between reduced levels of CSCs and adverse cardiovascular outcomes in different cohorts of patients. We also discuss potential mechanisms that explain this association. Beyond CSCs' ability to participate in cardiovascular repair, levels of CSCs need to be interpreted in the context of the broader connections between haematopoiesis and cardiovascular function, including the role of clonal haematopoiesis and inflammatory myelopoiesis.

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.

Low Pre-Treatment Count of Circulating Endothelial Progenitors as a Prognostic Biomarker of the High Risk of Breast Cancer Recurrence

Neoangiogenesis is mediated by circulating bone marrow-derived endothelial progenitors (circulating EPCs). The aim of the study was the quantification of circulating EPCs from the peripheral blood mononuclear cells of invasive breast cancer (IBrC) patients by flow cytometry, before and after cancer adjuvant treatment. A total of 88 stage IA-IIB primary IBrC patients were enrolled prospectively. Circulating EPCs with the immune-phenotype CD45−CD34+CD133+CD31+ were assessed. Treatment significantly reduced the number of EPCs/µL in the general IBrC cohort. However, there was a relevant elevation in the number of circulating EPCs after nine months of adjuvant treatment in the group of patients aged ≥ 55 years, of T2 clinical type, with nodal involvement (N1) and Ki67 expression > 15%. Follow-up revealed a significantly higher incidence of disease relapse in breast cancer patients with low pre-treatment circulating EPCs levels compared with those with a high baseline circulating EPCs count. The receiver-operating characteristic curve identified a tumour diameter of 2.1 cm as the best cut-off value to discriminate between disease-relapse subjects and non-relapse disease cases. Our study strongly indicates that, next to tumour diameter and Ki67 expression, circulating bone marrow-derived EPCs may serve as useful markers for predicting therapeutic outcomes as well as a future prognosis.

Levels of Circulating Progenitor Cells, Cardiovascular Outcomes and Death

Rationale:

Circulating progenitor cells (CPCs), including endothelial progenitor cells (EPCs) are biologically related to many aspects of cardiovascular disease, as they promote angiogenesis and vascular repair.

Objective:

We herein aimed to meta-analyze studies reporting the prognostic role of the CPC/EPC measure on cardiovascular outcomes and death.

Methods and Results:

We screened the English-language literature for longitudinal studies reporting the association between baseline CPC/EPC levels, future cardiovascular events, and death. We retrieved 28 studies, 21 of which contained poolable data and entered the meta-analysis, for a total of 4155 patients, mostly with a high baseline cardiovascular risk. Sixty percent of the studies met at least 11 of 16 items of quality assessment. Overall, reduced CPC/EPC levels were associated with a ≈2-fold increased risk of future cardiovascular events and cardiovascular death. The most predictive phenotype was CD34 + CD133 + : low versus high levels predicted cardiovascular events, restenosis after endovascular intervention, cardiovascular death, and all-cause mortality. Heterogeneity among studies and according to the CPC/EPC phenotype was generally high. Excluding studies for which the risk estimate had to be extrapolated or limiting the analyses to higher quality studies still indicated a significant risk for future cardiovascular events and death in patients with low versus high progenitor cell counts.

Conclusions:

This meta-analysis shows that a reduction in the levels of circulating cells putatively provided with vasculoregenerative properties represents a risk factor for adverse cardiovascular outcomes and death.