Investigating fibrosis and inflammation in an ex vivo NASH murine model

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease, characterized by excess fat accumulation (steatosis). Nonalcoholic steatohepatitis (NASH) develops in 15-20% of NAFLD patients and frequently progresses to liver fibrosis and cirrhosis. We aimed to develop an ex vivo model of inflammation and fibrosis in steatotic murine precision-cut liver slices (PCLS). NASH was induced in C57B1/6 mice on an amylin and choline-deficient L-amino acid-defined (CDAA) diet. PCLS were prepared from steatohepatitic (sPCLS) and control (cPCLS) livers and cultured for 48 h with LPS, TGF beta 1, or elafibranor. Additionally, C57B1/6 mice were placed on CDAA diet for 12 wk to receive elafibranor or vehicle from weeks 7 to 12. Effects were assessed by transcriptome analysis and procollagen I alpha 1 protein production. The diets induced features of human NASH. Upon culture, all PCLS showed an increased gene expression of fibrosis- and inflammation-related markers but decreased lipid metabolism markers. LPS and TGF beta 1 affected sPCLS more pronouncedly than cPCLS. TGF beta 1 increased procollagen I alpha 1 solely in cPCLS. Elafibranor ameliorated fibrosis and inflammation in vivo but not ex vivo. where it only increased the expression of genes modulated by PPAR alpha. sPCLS culture induced inflammation-, fibrosis-, and lipid metabolism-related transcripts, explained by spontaneous activation. sPCLS remained responsive to proinflammatory and profibrotic stimuli on gene expression. We consider that PCLS represent a useful tool to reproducibly study NASH progression. sPCLS can be used to evaluate potential treatments for NASH, as demonstrated in our elafibranor study, and serves as a model to bridge results from rodent studies to the human system. NEW & NOTEWORTHY This study showed that nonalcoholic steatohepatitis can be studied ex vivo in precision-cut liver slices obtained from murine diet-induced fatty livers. Liver slices develop a spontaneous inflammatory and fibrogenic response during culture that can be augmented with specific modulators. Additionally, the model can be used to test the efficacy of pharmaceutical compounds (as shown in this investigation with elafibranor) and could be a tool for preclinical assessment of potential therapies.