Abstract

BACKGROUND:

Little is known about the role of endothelial progenitor cells (EPCs) in atherosclerosis. Accordingly, we performed a series of assessments with hypercholesterolemic (apolipoprotein E-null [ApoE(-/-)]) and wild-type (WT) mice to evaluate how cholesterol influences reendothelialization, atherosclerosis, and EPC function after arterial injury.

METHODS AND RESULTS:

Unexpectedly, reendothelialization (assessed by resistance to Evans blue staining) and circulating EPC counts (EPC culture assay) were greater in ApoE(-/-) mice than in WT mice, and transplantation of ApoE(-/-) bone marrow in WT mice accelerated endothelial recovery and increased recruitment of bone marrow-derived EPCs to the neoendothelium. Cholesterol concentration-dependently promoted the proliferation (MTS assay) of both ApoE(-/-) and WT EPCs, and the concentration dependence of EPC adhesion (to vitronectin-, collagen type I-, fibronectin-, and laminin-coated plates), migration (modified Boyden chamber assay), and antiapoptotic (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling stain) activity was biphasic. Cholesterol enhanced the messenger RNA expression (quantitative, real-time reverse-transcription polymerase chain reaction) of vascular endothelial growth factor and inhibited Notch1 messenger RNA expression in both ApoE(-/-) and WT EPCs, whereas endothelial nitric oxide synthase messenger RNA expression increased in ApoE(-/-) EPCs and declined in WT EPCs after cholesterol exposure. EPC activity was greater in Notch1(+/-) EPCs than in WT EPCs, and transplantation of Notch1(+/-) bone marrow accelerated endothelial recovery after arterial injury in WT mice.

CONCLUSIONS:

The results presented here provide novel insights into the role of EPCs during atherosclerosis and suggest that cholesterol and Notch1 may be involved in the regulation of EPC activity.