Establishment and functional characterization of an in vitro model of the blood-brain barrier, comprising a co-culture of brain capillary endothelialcells and astrocytes

Objective: The aim was to establish a flexible, abundantly available, repro ducible and functionally characterized in vitro model of the blood-brain ba rrier (BBB). Methods: In a first step, bovine brain capillaries and newborn rat astrocytes were isolated. Subsequently, a co-culture of primary brain capillary endothelial cells (BCEC) on semi-permeable filter inserts, with a strocytes on the bottom of the filter was established. The cell material wa s characterized on the basis of specific cell-type properties and (function al expression of) specific BBB properties. Results: BCEC displayed: (1) cha racteristic endothelial cell morphology; (2) expression of endothelial cell markers (i.e., CD51, CD62P, CD71 and cadherin 5); (3) marginal F-actin loc alization; (4) tight junction formation between the cells; (5) expression o f gamma -glutamyl-transpeptidase (gamma -GTP); (6) expression of P-glycopro tein (Pgp); (7) functional transendothelial transferrin transport and uptak e; (8) restriction of paracellular transport; and (9) high transendothelial electrical resistance (TEER). Astrocytes displayed characteristic astrocyt e morphology and expressed glial fibrillary acidic protein (GFAP). Co-cultu re with astrocytes increased TEER and decreased paracellular transport. In addition, expression of the glucocorticoid receptor (GR) was demonstrated i n the endothelial cells of the BBB, while no expression of the mineralocort icoid receptor (MR) was found. Conclusions: A high quality and mass-product ion in vitro BBB model was established in which experiments with physiologi cal (e.g., regulation of BBB permeability), pharmacological (e.g., pharmaco kinetics and pharmacodynamics) and pathophysiological (e.g., disease influe nce on BBB permeability) objectives can be reproducibly performed. (C) 2001 Elsevier Science B.V. All rights reserved.