Molecular mechanisms that control endothelial cell contacts

Endothelial cell contacts control the permeability of the blood vessel wall . This allows the endothelium to form a barrier for solutes, macromolecules , and leukocytes between the vessel lumen and the interstitial space. Loss of this barrier function in pathophysiological situations can lead to extra cellular oedema. The ability of leukocytes to enter tissue at sites of infl ammation is dependent on molecular mechanisms that allow leukocytes to adhe re to the endothelium and to migrate through the endothelial cell layer and the underlying basal lamina. It is a commonly accepted working hypothesis that inter-endothelial cell contacts are actively opened and closed during this process. Angiogenesis is another important process that requires well- controlled regulation of inter-endothelial cell contacts. The formation of new blood vessels by sprouting from pre-existing vessels depends on the loo sening of established endothelial cell contacts and the migration of endoth elial cells that form the outgrowing sprouts. This review focuses on the mo lecular composition of endothelial cell surface proteins and proteins of th e cytoskeletal undercoat of the plasma membrane at sites of inter-endotheli al cell contacts and discusses the current knowledge about the potential ro le of such molecules in the regulation of endothelial cell contacts. Copyri ght (C) 2000 John Wiley & Sons, Ltd.