Refining and replacing models of hepatocytes and periportal fibrosis

Abstract

The liver plays an important role in drug toxicity, in part through its significant expression of drug-metabolising enzymes. For this reason, liver cells are often used in toxicity screening. Chronic liver injury is also a growing health concern, but its study in-vivo is limited by the severity of the bile duct ligation (BDL) animal model. In investigating ways to replace animals as a source of liver cells for toxicity screening and reduce and refine the BDL model, rat AR42J-B-13 (B-13) cells have been examined as an alternative to primary hepatocytes and chemical alternatives to BDL have been examined respectively. B-13 cells were readily converted by glucocorticoid treatment to hepatocyte-like (B-13/H) cells, which expressed functional CYP1A and CYP3A sub-families whose expression could be induced in response to prototypical inducers. CYP2B1 could be induced at mRNA but not protein level. The CYP1A2 gene in B-13 cells was disrupted/non-functional, however stable introduction of human CYP1A2 showed B-13 cells could be humanised and used for assessment of bioactivation-dependent genotoxins. Drug transporter mRNA expression was low in B-13 and B-13/H cells, but HNF4α overexpression enhanced transporter mRNA expression and function in B-13/H cells. The chronic administration of methapyrilene and α-naphthylisothiocyanate in rats and mice respectively, caused liver injury qualitatively equivalent to that seen after BDL but without the associated mortality or severity seen with BDL. These data suggest that B-13/H cells could be used as an alternative to primary hepatocytes for drug toxicity screening. Chronic administration of methapyrilene and α-naphthylisothiocyanate could be used as alternative less severe models of periportal fibrosis in rats and mice respectively. Use of B-13/H cells would reduce the number of animals required for hepatocyte derivation and through refinement of the BDL model of periportal fibrosis, fewer rodents would be subject to the associated complications and high mortality rate of BDL.