In vitro isolation of circulating endothelial progenitor cells is related to the high density lipoprotein plasma levels

Circulating endothelial progenitor cells (EPCs) play an important role in post natal neovascularization. High density lipoproteins (HDL) protect the vascular wall from atherosclerosis. The role exerted by HDL on EPCs physiology is unknown. In this study we investigated whether the levels of plasma HDL can modulate the number of EPCs. The number of EPCs was evaluated in 24 subjects as the number of endothelial colony-forming unit (e-CFU) growth in culture. The number of AC133 positive progenitor cells present in the gate of the CD34 bright positive lymphocytes was also evaluated. Plasma levels of HDL, triglycerides and total cholesterol/HDL cholesterol ratio correlated with the number of e-CFU (r=0.62, P=0.006; r=-0.54, P=0.019, and r=-0.61, P=0.007 respectively), but not with the number of CD34/AC133 positive progenitor cells. In vitro, the incubation of the mononuclear cellular fraction with HDL did not increase the number of e-CFU in culture, whereas LDL and VLDL reduced the number of e-CFU. Our results indicate that human HDL plasma levels directly relate to the number of circulating endothelial progenitor cells that can be isolated in vitro, as determined by the number of e-CFU