Expression and transport function of drug uptake transporters in differentiated HepaRG cells.

HepaRG cells have the ability to differentiate into hepatocyte-like cells. Many papers have shown that these hepatocyte-like cells share several functional properties with intact human hepatocytes. However, although previous studies have indicated the partial maintenance of mRNA expression of drug transporters, their expression and function have not been quantitatively characterized. In the present study, the mRNA and protein expression levels and transport activities of hepatic uptake transporters, organic anion transporting polypeptides (OATPs) and Na(+)-taurocholate cotransporting polypeptide (NTCP) in HepaRG cells were compared with those in cryopreserved human hepatocytes. The mRNA expression levels of OATP1B1, OATP1B3, OATP2B1, and NTCP in HepaRG cells were 22-38%, 2-15%, 82-113%, and 191-247% of those in human hepatocytes, respectively. The relative protein expression of these transporters was comparable with their mRNA expression. We observed saturable uptake of typical substrates of NTCP and OATPs except for cholecystokinin octapeptide (OATP1B3-selective substrate), and Na(+)-dependent uptake of taurocholate was confirmed. Their relative uptake clearances were well explained by their mRNA and protein expression levels. Additionally, inhibition potencies of 12 OATP1B1 inhibitors were investigated both in HepaRG cells and in OATP1B1-expressing HEK293 cells to demonstrate the usefulness of HepaRG cells for the characterization of OATP1B1-mediated drug-drug interactions. The Ki values in both cell lines were comparable and showed significant correlation. These results suggest that the hepatic uptake transport function of OATP and NTCP transporters was relatively well maintained in HepaRG, although OATP1B3 function was too low to be detected.