Endothelial progenitor cells: quod erat demonstrandum?

A constantly growing body of research has been performed mainly over the past decade and a half, aiming to facilitate our still limited understanding of the biology and function of various different cell types which collectively have been termed endothelial progenitor cells. This review intends to critically outline aspects of terminology, origin and applicability of the somatic progenitors which are thought to maintain integrity and support regeneration of the inner lining of vessels through proliferation. Despite reasonable progress in the field, we are still not confident regarding the precise phenotype and function of endothelial progenitor cells. Model systems that have been developed to study the vascular regenerative potential of human endothelial progenitor cells in animal models in vivo present principle tools for testing new agents that modulate vascular homeostasis and regeneration.