Levels of circulating CXCR4-positive cells are decreased and negatively correlated with risk factors in cardiac transplant recipients.

The association between levels of circulating endothelial progenitor cells (EPCs) and heart transplant recipients (HTX) with cardiac allograft vasculopathy (CAV) is under debate. The chemokine receptor CXCR4 plays an important role in the mobilization of progenitor cells and is implicated in pathological conditions, including cardiovascular disease. This study aims to evaluate the association between EPCs and CXCR4-positive cells in HTX patients. Peripheral blood mononuclear cells (PBMCs) from 34 HTX patients and 25 control participants were analyzed by flow cytometry for CXCR4-positive cells and EPCs. Endothelial progenitor cells were defined by the expression of a range of hematopoietic and endothelial lineage markers in different combinations. The ability to form endothelial cell colonies in vitro was also assessed by colony-forming unit (CFU) assay. Phenotypic analysis of EPCs by flow cytometry revealed similar levels in HTX patients compared to controls. In addition, no difference was observed between levels of EPCs or CFU number in patients with and without CAV. By contrast, CFU assay revealed a reduced number of CFUs in HTX patients compared to controls (3.3% ± 0.95 and 13.3% ± 4.5%, respectively, P = 0.014). Likewise, levels of CXCR4-positive cells were significantly reduced (15.9 ± 1.4 in patients vs 24.8 ± 3.3% in controls, P < 0.01), negatively correlated with Framingham risk score (rho = -0.4, P = 0.02) and the number of risk factors (rho = -0.3, P = 0.049). Levels of CXCR4-positive cells were also correlated with CFU number (r = 0.65, P = 0.0005). These findings further develop our understanding of the role of EPCs and endothelial CFUs in cardiovascular disease, in addition to highlighting the potential importance of CXCR4 in heart transplantation.

Reduced levels of putative endothelial progenitor and CXCR4+ cells in coronary artery disease: kinetics following percutaneous coronary intervention and association with clinical characteristics.

Levels of circulating endothelial progenitor cells (EPCs) and CXCR4-positive cells are decreased in patients with coronary artery disease (CAD); however, their ability to change in response to acute vascular injury remains to be elucidated. Progenitor and CXCR4-positive cells were analysed by flow cytometry from the peripheral blood of 23 healthy controls and 23 patients with CAD, of which 13 patients underwent angiogram and 10 patients received percutaneous coronary intervention (PCI) with stent implantation. Baseline levels of progenitor and CXCR4-positive cells were substantially reduced in CAD patients compared to controls, although they were still capable of increasing in response to vascular injury. Levels of progenitor and CXCR4-positive cells were increased to a greater extent in the PCI group compared to angiogram patients. At presentation, levels of putative endothelial progenitor and CXCR4-positive cells were found to be negatively correlated with disease severity. A one-year follow-up revealed that out of the cell populations examined, only levels of CXCR4-positive cells were positively correlated with angina frequency in the PCI group, but not in patients receiving angiogram. Baseline levels of progenitor cells are differentially increased depending upon the severity of vascular injury incurred, regardless of a significant deficit in baseline levels in CAD patients. Levels of putative EPCs and CXCR4-positive cells were negatively correlated with disease severity at presentation, however, only CXCR4-positive cells were associated with patient condition in a one-year follow-up.

Human rheumatoid synoviocytes express functional P2X7 receptors.

Human type B synoviocytes are involved in joint injury during rheumatic diseases by producing inflammatory mediators such as interleukin-6 (IL-6). The increased level of purine and pirimidine nucleotides in the synovial fluid of rheumatoid arthritis (RA) patients could activate the large family of P2 receptors. Thus, we investigated the presence of P2 receptors in human type B synoviocytes from rheumatoid joints, also evaluating whether the P2X7 receptor is involved in IL-6 release. Reverse transcriptase polymerase chain reaction analysis revealed messenger ribonucleic acid (mRNA) expression for the P2X1, P2X2, P2X4, P2X5, P2X6, P2X7, P2Y1, P2Y4, P2Y11, P2Y12, P2Y13, and P2Y14 but not the P2X3, P2Y2, and P2Y6 receptors. The expression of the P2X7 receptor was confirmed by Western blot analysis. Adenosine triphosphate (ATP) and the P2X7 receptor agonist 2'-3'-O-(4-benzoylbenzoyl)ATP (BzATP) triggered an increase in intracellular calcium, thereby suggesting the expression of functional P2 receptors, including the P2X7 receptor. Moreover, BzATP treatment upregulated both IL-6 mRNA and protein expression. Synoviocytes spontaneously released low quantities of IL-6; the incubation with BzATP induced the release of larger amounts of the cytokine, and such a release was blunted by the P2X7 antagonist oxidized ATP. The selective P2X1 and P2X3 receptor agonist alpha,beta-methylene ATP did not affect IL-6 release. Finally, BzATP failed to induce a significant uptake of the large-molecule YO-PRO, thus suggesting the lack of pore formation after P2X7 receptor stimulation. In conclusion, among the different P2 receptors expressed on human RA type B synoviocytes, the P2X7 receptor may modulate IL-6 release but not inducing changes in cell membrane permeability.