Circulating endothelial cells: realities and promises in vascular disorders

Endothelial contribution to human vascular disorders is difficult to investigate, owing to the paucity of non-invasive methods and of specific endothelial markers . Circulating endothelial cells (CECs) might be used asa surrogate non-invasive marker for the study of vascular alterations. To address this problem, we produced an antibody against the endothelial molecule CD126 (S-Endol) and developed, in the nineties, an original and sensitive immunomagnetic separation assay. Using this approach, we demonstrated elevated number of CECs in clinical diseases linked with vascular injury like heart catheterization, sickle cell anemia,bacterial infection, thrombotic thrombocytopenic purpura or acute coronary syndromes. CECs correspond to very rare cells present in blood since levels in the range of 3 cells/ml are detectable in these pathologies. Several clinical interest of CECs will be discussed including their relevance as marker of disease activity, severity or treatment efficacy, or their use in diagnostic tests. The origin of endothelial cells in peripheral blood is difficult to establish. They could correspond to endothelial cells dislodged from the vessels in response to injury. It was subsequently shown that a subset of CECs comprised a population of bone marrow-derived endothelial progenitors that participate in angiogenesis. Identification of the origin and characteristics of CECs provides fascinating insights into endothelial cell pathophysiology. Moreover, CECs constitute original and promising tools for diagnosis, prognosis and therapy of vascular disorders.