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)-4, while aberrantly expressed bile ductular markers, including cytokeratin 19 (CK 19) and spermatogenic immunoglobulin superfamily (SgIGSF). Among the cytokines examined, tumor necrosis factor (TNF)- inhibited expression of albumin and HNF-4, both at mRNA and protein levels. After culturing for 2 weeks with TNF-, 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- 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- promotes the ductular transdifferentiation of hepatocytes and suggest a role of TNF- in the pathogenesis of ductular reaction. J. Cell. Biochem. 114: 831843, 2013. (c) 2012 Wiley Periodicals, Inc.