Abstract
Biliary excretion via drug-metabolizing enzymes and transporters is often critical as the hepatobiliary disposition is directly linked to drug efficacy and safety. Biliary excretion of drugs is mediated by transporters localized in the bile canalicular membrane of hepatocytes. Inhibition of the transporters may induce drug interactions and drug-induced cholestasis by parental drugs or their metabolites. Since there are species differences in the process, an in vitro evaluation system using human hepatocytes considered to be useful for drug discovery and development. However, conventional human primary cultured hepatocytes formed the closed bile lumen between hepatocytes, and thus it is technically difficult to collect the biliary-secreted drug. To overcome the challenge, the present study aimed to construct a human hepatocyte culture system that can collect bile components. Screening for a factor promoting bile duct formation in hepatocytes, the adhesion protein claudins were extracted. When human hepatocytes were cultured on a permeable support coated with claudin proteins, open hemi-luminal morphology was newly formed on the surface of the permeable support. This hepatocyte culture model, icHep (induced open-form canalicular hepatocyte), maintained the functions of a wide range of liver-specific drug uptake transporters and metabolizing enzymes. Permeation assay in icHep showed unidirectional transport of typical substrate of biliary transporters from blood to bile side. Furthermore, the estimated biliary drug excretion from the permeability obtained in icHep was well-correlated with the reported human in vivo values. This approach is useful to assess pharmacokinetics and drug safety during the preclinical stage of drug discovery and development.
