Engineered fibroblast growth factor 19 reduces liver injury and resolves sclerosing cholangitis in Mdr2‐deficient mice

Defects in multidrug resistance 3 gene (MDR3), which encodes the canalicular phospholipid flippase, cause a wide spectrum of cholangiopathy phenotypes in humans. Mice deficient in Mdr2 (murine ortholog of MDR3) develop liver diseases that closely reproduce the biochemical, histological, and clinical features of human cholangiopathies such as progressive familial intrahepatic cholestasis and primary sclerosing cholangitis. We hypothesized that modulating bile acid metabolism by the gut hormone fibroblast growth factor 19 (FGF19) may represent a novel approach for treating cholangiopathy and comorbidities. We introduced adeno‐associated virus carrying the gene for either the endocrine hormone FGF19 or engineered FGF19 variant M70 to 12‐week old Mdr2‐deficient mice with fully established disease. Effects on serum levels of liver enzymes, liver histology, and bile acid homeostasis were evaluated. FGF19 and M70 rapidly and effectively reversed liver injury, decreased hepatic inflammation, attenuated biliary fibrosis, and reduced cholecystolithiasis in Mdr2‐deficient mice. Mechanistically, FGF19 and M70 significantly inhibited hepatic expression of Cyp7a1 and Cyp27a1, which encode enzymes responsible for the rate‐limiting steps in the classic and alternate bile acid synthetic pathways, thereby reducing the hepatic bile acid pool and blood levels of bile acids. Importantly, prolonged exposure to FGF19, but not M70, led to the formation of hepatocellular carcinomas in the Mdr2‐deficient mice. Furthermore, M70 ameliorated the hepatosplenomegaly and ductular proliferation that are associated with cholangiopathy. Conclusion: These results demonstrate the potential for treating cholangiopathy by safely harnessing FGF19 biology to suppress bile acid synthesis. (Hepatology 2016;63:914–929)