Inflammation and Fibrosis in the Livers of TNFR1/Mdr2ko Mice

Hepatocellular carcinoma (HCC) develops in chronically inflamed livers with advanced fibrosis in 90% of all cases. The multidrug resistance protein 2 knockout (Mdr2ko) mice are a well-established model for chronic hepatitis and inflammation-associated HCC. Tumor necrosis factor receptor-1 (TNFR1) mediated signaling is known to induce epithelial cell death, inflammation, and fibrosis. This study aims to analyze whether an additional knockout of TNFR1 in the Mdr2ko mouse model would reduce hepatic inflammation and fibrosis, which could consequently delay HCC development.

Tissue injury was assessed by plasma analysis of ALT and ALP levels. Hepatic immune phenotyping was determined by FACS analysis. Inflammation and fibrosis were evaluated by histological analysis of H&E stained liver slices. ECM deposition was analyzed by quantifying the hepatic hydroxyproline content and Sirius Red staining. Real time RT PCR was applied to analyze hepatic expression levels of targets involved in inflammation (IL-1β, TNFα), matrix remodeling (Collagen, MMPs, TIMPs, α-sma), tumor development (AFP, A20, OPN).

ALT and ALP levels were increases in TNFR1/Mdr2ko mice, which is indicative of more severe tissue damage. TNFR1/Mdr2ko mice showed significantly increased hepatic hydroxyproline contents. Real time RT-PCR showed elevated expression levels of genes involved in fibrosis, inflammasome activity, necroptosis and possibly malignant transformation.

The absence of TNFR1 mediated signaling does not improve the pathological phenotype of Mdr2ko mice. It instead exacerbated tissue damage possibly through alternative forms of cell death, which results in an increased fibrotic response. Long-term studies will have to show whether this will affect the tumor incidence in the Mdr2ko mouse model.