Confluent monolayers of bile duct epithelial cells with tight junctions.

The culture of fully differentiated intrahepatic bile duct epithelial cells (IBDECs) to use as a model for the in vivo intrahepatic biliary tract has not been established. IBDECs from normal rat livers were grown on a collagen-coated permeable filter and formed a confluent monolayer 7 days after being plated. Positive reactions for cytokeratin-19 and retained gamma-glutamyl transpeptidase (GGTP) activity were shown. The transepithelial electrical resistance between the apical and the basolateral compartment culture chambers increased with the culture age and plateaued after the 7th day. The resulting cultured cells displayed a number of characteristics. (1) The cells formed a thin, continuous monolayer and displayed microvilli on the apical surface and junctional complexes between the cells, consistent with in vivo IBDECs. (2) Cells cultured for more than 7 days prevented the passage of horseradish peroxidase (HRP) and ruthenium red through paracellular pathways. (3) Seven-day-old cultures displayed a mean transepithelial electrical resistance of 137.3 omega-cm2, which decreased by 27.1% from its initial level after cell treatment with ethylenediamineteraacetic acid (EDTA). These results indicate that confluent IBDEC monolayers are well differentiated and polarized with tight junctions (TJs) between the cells. These cell monolayers can provide a useful and relevant model for the in vitro study of various in vivo bile duct phenomena.