Three-Dimensional Spheroid Culture of Endothelial Cells

Abstract

Endothelial cells (EC) line the inside of all blood vessels as a monolayer and contact smooth muscle cells (SMC) or pericytes (PC) through breaks in the underlying basement membrane (BM). EC do not proliferate under these conditions and are referred to as “quiescent”. Primary EC populations are usually cultured in vitro as two-dimensional flat monolayers which reflect some of the properties of the endothelium in vivo (Pauly et al. 1992).Nevertheless, EC cultured in monolayer configuration are never completely quiescent and up to 10 % of EC proliferate even in a confluent monolayer. Furthermore, monolayer EC gradually dedifferentiate and lose their distinct organ-specific and caliber-specific morphological and functional characteristics. For example, CD34, which is constitutively expressed by most EC in vivo, is rapidly downregulated upon transfer into tissue culture (Delia et al. 1993). Similarly, cultured brain EC lose their tight-junction-dependent blood-brain barrier characteristics (Wolburg et al. 1994).