Development of a humanized in vitro blood-brain barrier model to screen for brain penetration of antiepileptic drugs

Purpose: A biotechnologic breakthrough for the study of drug permeability across the blood-brain barrier (BBB) would be the use of a reproducible in vitro model that recapitulates the functional, structural, and pathologic properties of the BBB in situ. We developed a humanized dynamic in vitro BBB model (DIV-BBB) based on cocultures of human microvascular endothelial cells (HBMECs) from normal and drug-resistant epileptic brain tissue with human brain astrocytes (HAs) from epilepsy patients or controls. Methods: HBMECs and HAs were cocultured for 28 days in polypropylene capillaries. HBMECs were exposed to physiologic levels of shear stress generated by intraluminal flow. Permeability to [H-3]sucrose, [C-14]phenytoin, and [C-14]diazepam was measured in control and drug-resistant DIV-BBB with and without pretreatment with the MDR1 inhibitor XR9576. BBB integrity was monitored by transendothelial electrical resistance measurements (TEERs). Cell growth and viability were assessed by measurement of glucose consumption and lactate production. Results: P-Sucrose and TEER values did not depend on the origin of the endothelium used (epileptic or normal). P-Phenytoin was 10-fold less (1.54 x 10(-6) cm/s) in drug-resistant BBB models than in controls (1.74 x 10(-5) cm/s). MDR1 blockade with XR9576 was effective (3.5-fold increase) only in drug-resistant cultures. P-Diazepam in control and drug-resistant DIV-BBB was not affected by XR9576 and did not depend on the epileptic or control origin of endothelia. The overall contribution of epileptic glia to pharmacoresistance was negligible. Conclusions: These results show that, for the substances used, the humanized DIV-BBB recapitulates the physiologic permeability properties of the BBB in vivo and is also capable of mimicking a drug-resistant BBB phenotype.