Urea-induced ROS accelerate senescence in endothelial progenitor cells

Background and aims: The pathogenic events responsible for the reduction of endothelial progenitor cell (EPC) number and function seen in patients with chronic renal failure (CRF) are poorly understood. Here we investigate the hypothesis that increased concentrations of urea associated with CRF increase ROS production directly in EPCs, causing abnormalities associated with coronary artery disease risk. Methods: Human EPCs were isolated from peripheral blood mononuclear cells of healthy donors and cultured in the presence or absence of 20 mmol/L urea. Results: Urea at concentrations seen in CRF induced ROS production in cultured EPCs. Urea-induced ROS reduced the number of endothelial cell colony forming units, uptake and binding of Dil-Ac-LDL and lectin-1, and the ability to differentiate into CD31- and vascular endothelial growth factor receptor 2 epositive cells. Moreover, urea-induced ROS generation accelerated the onset of EPC senescence, leading to a senescence-associated secretory phenotype (SASP). Normalization of mitochondrial ROS production prevented each of these effects of urea. Conclusions: These data suggest that urea itself causes both reduced EPC number and increased EPC dysfunction, thereby contributing to the pathogenesis of cardiovascular disease in CRF patients.