Cultures of primary bovine brain endothelial cells (BECs) grown, often together with astrocytes, on permeable supports in two-compartment culture systems are commonly used as an in vitro model of the blood-brain barrier (BBB). While trans-endothelial electrical resistance, restriction of paracellular transport and expression of relevant transport systems, receptors and tight junction proteins has been thoroughly investigated, the expression of BBB specific genes during culture of the bovine BECs is less understood. Optimally, the gene expression of bovine BECs cultured in vitro should resemble the in vivo gene expression of brain capillary endothelial cells.
Primary bovine endothelial cells and rat astrocytes were cultured in different culture configurations and the mRNA expression of selected genes (vWF, Glut-1, P-gp, claudin-1,-5, occludin, JAM-1, LAT-1, SLC16A1, MRP-1,-4, BCRP, ZO-1, AP, TPA and SLCO4A1) was investigated by qPCR and compared with the expression in freshly isolated bovine capillaries.
Occludin was the only tight junction protein where a decrease in mRNA expression from capillaries to culture configurations was observed. JAM-1 and ZO-1 maintained mRNA expression, while an increase in mRNA expression from capillaries to all culture configurations was observed for claudin-1. Efflux pumps MRP-1 and -4 were up-regulated, while a down-regulation was observed for BCRP. LAT-1, SLC16A1 and TPA showed a dramatic decrease in mRNA-expression from capillaries to all culture configurations, while SLCO4A1 showed a significant increase. It could be advantageous to investigate whether an up-regulation of certain BBB specific genes is possible and would have an impact on e.g. paracellular tightness.