Introduction

Brain microvascular endothelial cells have successfully been maintained in culture for some time by many groups, but it has proved to be very difficult to establish a true in vitro model of the blood–brain barrier (BBB). Although a few promising protocols have been published fairly recently, reproducibility appears to be problematic as judged by the scarcity of studies in which these protocols have been adopted.

The present chapter does not aim at providing an overview on brain endothelial cells in culture. For this the reader is referred to reviews by Rubin (1991), Joó (1992) and Laterra & Goldstein (1992, 1993). Nor is it the intention to present a new protocol for the isolation and growth of these cells in culture. One protocol is given at the end of the chapter, otherwise the reader will be referred to the literature. Instead the focus will be on specific problems associated with the pursuit of establishing an in vitro model of the BBB, mainly on aspects such as differentiation of endothelial cells in culture and on evaluation and characterisation of such culture systems. It is meant to be a guide for those who plan to grow brain microvascular endothelial cells in culture.

Brain versus peripheral endothelial cells

Paul Ehrlich observed in 1885 that dye injected into the vasculature of animals readily penetrated all tissues except the brain. About 80 years later it was shown in similar tracer experiments that the structural basis for this ‘blood–brain barrier’ is the endothelial cells which constitute the microvascular walls in the brain.