MORPHOLOGICAL AND FUNCTIONAL-CHARACTERIZATION OF AN IN-VITRO BLOOD-BRAIN-BARRIER MODEL

Cell culture models have been extensively used for studies of blood-br ain barrier (BBB) function. However, several in vitro models fail to r eproduce some, if not most, of the physiological and morphological pro perties of in situ brain microvascular endothelial cells. We have rece ntly developed a dynamic, tridimensional BBB model where endothelial c ells exposed to intraluminal flow form a barrier to ions and proteins following prolonged co-culturing with glia. We have further characteri zed this cell culture model to determine whether these barrier propert ies were due to expression of a BBB phenotype. Endothelial cells of hu man, bovine or rodent origin were used. When co-cultured with glia, in traluminally grown endothelial cells developed features similar to in vivo endothelial cells, including tight junctional contacts at interdi gitating processes and a high transendothelial resistance. This in vit ro BBB was characterized by the expression of an abluminal, ouabain-se nsitive Na/K pump, and thus favored passage of potassium ions towards the lumen while preventing Kf extravasation. Similarly, the in vitro B BB prevented the passage of blood-brain barrier-impermeant drugs (such as morphine, sucrose and mannitol) while allowing extraluminal accumu lation of lipophylic substances such as theophylline. Finally, express ion of stereo-selective transporters for Aspartate was revealed by tra cer studies. We conclude that the in vitro dynamic BBB model may becom e an useful tool for the studies of BBB-function and for the testing o f drug passage across the brain endothelial monolayer. (C) 1997 Elsevi er Science B.V.