Functional Analysis of Induced Human Ballooned Hepatocytes in a Cell Sheet-Based Three Dimensional Model.

Ballooned hepatocytes (BH) are a key histological hallmark of nonalcoholic steatohepatitis (NASH), yet their consequences for liver-specific functions are unknown. In our previous study, an experimental model of human induced-BHs (iBH) has been successfully developed based on cell sheet technology. This study aimed to determine the functions of iBHs in the primary human hepatocyte/normal human dermal fibroblast (PHH/NHDF) co-culture cell sheets. Normal hepatocytes in the PHH/3T3-J2 co-culture cell sheets were set as a control, since 3T3-J2 murine embryonic fibroblasts have exhibited previously long term maintenance of PHH functions. It was found that, albumin secretion was not affected in iBHs, but urea synthesis as well as cytochrome P450 enzyme (CYP) activities including CYP1A2 and CYP3A4, were significantly reduced in iBHs. Besides, loss of bile canaliculi was observed in iBHs. These findings are consistent with clinical studies of human NASH. In addition, PHH/NHDF cell sheets demonstrated two fold higher TGF-β1 secretion compared with PHH/3T3-J2 cell sheets. Furthermore, treatment with a TGF-β inhibitor and a semi-synthetic bile acid analogue (obeticholic acid, phase 3 trial of NASH therapy) ameliorated the histological appearance of established iBHs. In summary, this study demonstrates the priority of iBHs in recapitulating not only histology but also clinically relevant hepatic dysfunctions in human NASH and suggests TGF-β and bile acid related signal pathway may play important roles in the formation of iBHs.