Hepatocyte-specific knockout of HIF-2a cannot alleviate carbon tetrachloride-induced liver fibrosis in mice

Abstract

Background: The effects of hypoxia inducible factor-2a (HIF-2a) deficiency on liver fibrosis have not been demonstrated in a fibrosis model induced by carbon tetrachloride (CCl4). We aimed to examine whether hepatocyte-specific HIF-2a deletion could ameliorate CCl4-induced liver fibrosis in mice. Methods: Hepatocyte-specific HIF-2a knockout mice were created using an albumin promoter-driven Cre recombinase. HIF-2a knockout (KO) mice and floxed control wild-type (WT) mice were fed a normal diet (ND) and received either twice weekly intraperitoneal injections of CCl4 solution (CCl4 dissolved in olive oil) or the corresponding amount of olive oil for 8 weeks. The indicators of liver function, glucose and lipid metabolism, and liver histology were compared among the different groups. Results: Hepatocyte-specific HIF-2a knockout had no effect on the growth, liver function, glucose or lipid metabolism in mice. CCl4-treated KO and WT mice had a similar pattern of injury and inflammatory cell infiltration in the liver. Quantification of Masson staining, a-smooth muscle actin (a-SMA) immunohistochemistry, and the hydroxyproline (HYP) content revealed similar liver fibrosis levels between KO and WT mice injected intraperitoneally with CCl4. Immunohistochemistry analysis suggested that HIF-2a was mainly expressed in the portal area and hepatic sinusoids but not in hepatocytes. Bioinformatics analyses further indicated that HIF-2a expression was neither liver specific nor hepatocyte specific, and the effect of HIF-2a in hepatocytes on liver fibrosis may not be as important as that in liver sinuses. Conclusions: Hepatocyte HIF-2a expression may not be a key factor in the initiation of liver fibrogenesis, and hepatocyte-specific deletion of HIF-2a may not be the ideal therapeutic strategy for liver fibrosis.