Circulating endothelial cells and endothelial progenitors as surrogate biomarkers in vascular dysfunction

An increase in the number of circulating endothelial cells (CECs) and of bone marrow derived endothelial progenitors (CEPs) in the peripheral blood (PB) is normally associated with vascular injury, repair, and neovascularization. These cells rarely exist in the PB of healthy individuals. Therefore, when they are present in the PB of individuals, their phenotypes and quantity in the PB may serve as surrogate diagnostic or prognostic parameters of vascular injury and/or as an indication of tumor growth. An elevated level of CEPs may suggest an ongoing repair of ischemic vascular injuries and/or angiogenesis. Recently, more advanced techniques for CEC isolation and CEP enumeration have become available. In particular, immunobeads isolation and fluorescence-activated cell sorting (FACS) techniques have been employed with success in evaluation of vascular dysfunctions. Therefore, CECs and CEPs may serve as potential surrogate markers for monitoring various vascular diseases, which could help to determine pathological process and clinical treatment. In this article, we will present an overview of CECs and CEPs by discussing their origins, reviewing methodologies adapted to the measurement of rare events, describing pathological situations associated with CECs/CEPs, and correlating them with a broad spectrum of disease processes.