Objective-Circulating endothelial progenitor cells (EPCs) contribute to postnatal angiogenesis. The number of circulating EPCs has an inverse correlation with coronary risk scores. However, the effect of smoking on the number of circulating EPCs is not well-known. Methods and Results-We examined the effects of chronic smoking and of smoking cessation on EPC levels. Circulating EPCs were quantified by flow cytometry as CD45

Notch receptors are important mediators of cell fate during embryogenesis, but their role in adult physiology, particularly in postnatal angiogenesis, remains unknown.