Tumor necrosis factor-α promotes bile ductular transdifferentiation of mature rat hepatocytes in vitro

We previously showed that mature hepatocytes could transdifferentiate into bile ductular cells when placed in a collagen‐rich microenvironment. To explore the mechanism of transdifferentiation, we examined whether inflammatory cytokines affected the phenotype of hepatocytes in a three‐dimensional culture system. Spheroidal aggregates of rat hepatocytes were embedded within a type I collagen gel matrix and cultured in the presence of various cytokines. In the control, hepatocytes gradually lost expression of albumin, tyrosine aminotransferase, and hepatocyte nuclear factor (HNF)‐4α, while aberrantly expressed bile ductular markers, including cytokeratin 19 (CK 19) and spermatogenic immunoglobulin superfamily (SgIGSF). Among the cytokines examined, tumor necrosis factor (TNF)‐α inhibited expression of albumin and HNF‐4α, both at mRNA and protein levels. After culturing for 2 weeks with TNF‐α, hepatocytic spheroids were transformed into extensively branching tubular structures composed of CK 19‐ and SgIGSF‐positive small cuboidal cells. These cells responded to secretin with an increase in secretion and expressed functional bile duct markers. TNF‐α also induced the phosphorylation of Jun N‐terminal kinase (JNK) and c‐Jun, and the morphogenesis was inhibited by SP600125, a specific JNK inhibitor. Furthermore, in chronic rat liver injury induced by CCl4, ductular reaction in the centrilobular area demonstrated strong nuclear staining of phosphorylated c‐Jun. Our results demonstrate that TNF‐α promotes the ductular transdifferentiation of hepatocytes and suggest a role of TNF‐α in the pathogenesis of ductular reaction. J. Cell. Biochem. 114: 831–843, 2013. © 2012 Wiley Periodicals, Inc.