Induction of blood-brain barrier properties in immortalized bovine brain endothelial cells by astrocytic factors

The blood-brain barrier (B-BB) protects the free passage of substances into the brain and maintains the homeostasis of the central nervous system. It is commonly accepted that astrocytes surrounding brain endothelial cells in fluence the B-BB formation and the exhibition of B-BB function of capillari es. To begin the in vitro study on the B-BB, it is essential to obtain a ho mogenous and sufficient supply of brain endothelial cells as well as astroc ytes. We thus immortalized the bovine brain endothelial cell (BBEC) by tran sfection of the SV40 large T antigen and obtained a single clone, t-BBEC-11 7, which retained the brain endothelial cell phenotype. Astrocyte in co-cul ture was found to tighten the intercellular contacts of the immortal cells resulting in a reduced L-glucose permeability, and its conditioned medium ( CM) augmented a B-HB phenotype, alkaline phosphatase (ALP) activity. Among known astrocytic factors, only fibroblast growth factor-basic (bFGF) could mimic the actions of astrocytes as measured by L-glucose permeability and A LP activity. Moreover, anti-bFGF antibody canceled 90% of ALP activation by astrocyte CM. Basic FGF, however, failed to induce other B-BB phenotypes s uch as the expressions of multidrug resistance (mdr) and glucose transporte r (GLUT-1) genes. These data suggest that bFGF is one of the most plausible astrocytic factors to induce the B-BB properties of immortal brain endothe lial cells together with some unknown factors in the astrocyte CM. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.