Introduction: Bone marrow-derived endothelial progenitor cells (EPCs) circulate in the peripheral blood and are involved in endothelial homeostasis and repair.
Aim: The aim of this study was to assess the circulating levels of different EPC phenotypes in overweight men with or without erectile dysfunction (ED). As endothelial dysfunction is considered a necessary link with ED, endothelium-dependent vasodilation and its relation with EPCs were also investigated.
Methods: We studied 30, otherwise healthy, overweight subjects with symptomatic ED for at least 6 months, and 30 age- and weight-matched subjects without ED. Erectile function was assessed by completing the International Index of Erectile Function (IIEF-5), which consists of items 5, 15, 4, 2, and 7 from the full-scale IIEF-15.
Main outcome measures: Seven subpopulations of EPCs were determined by flow cytometry on the basis of the surface expression of CD34, CD133, and KDR antigens: CD34(+), CD133(+), KDR(+), CD34(+)CD133(+), CD34(+)KDR(+), CD133(+)KDR(+), and CD34(+)CD133(+)KDR(+). Endothelium-dependent flow-mediated dilation (FMD) was evaluated in the right brachial artery with a high-resolution ultrasound machine following reactive hyperemia.
Results: CD34(+)KDR(+) cell count was significantly lower in men with ED as compared with men without ED (63.1 +/- 4 vs. 92.4 +/- 6 cells/10(6) events, mean +/- standard error, P < 0.01). There was a significant direct correlation between circulating CD34(+)KDR(+) cells and the IIEF score (r = 0.44; P = 0.01): men with the severe form of ED presented the lowest level of circulating EPC CD34(+)KDR(+) cells. No significant correlation was found between the circulating levels of the other EPC phenotypes and the IIEF score. There was a significant correlation between CD34(+)KDR(+) cell count and FMD (r = 0.45; P = 0.01), but not between FMD and the other phenotypes.
Conclusions: Circulating levels of CD34(+)KDR(+) EPC are reduced in overweight subjects with ED and correlate with the severity of ED. Other EPC phenotypes are not related to ED, suggesting that the CD34(+)KDR(+) phenotype of EPCs may be preferred in future studies.