Abstract
BACKGROUND: Extracellular matrix protein 1 (ECM1) can inhibit TGFβ activation, but its antifibrotic action remains largely unknown. This study aims to investigate ECM1 function and its physical interaction with the profibrotic connective tissue growth factor (CTGF) in fibrosis and ductular reaction (DR). METHODS: Ecm1 knockouts or animals that ectopically expressed this gene were subjected to induction of liver fibrosis and DR by feeding 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) or α-naphthyl-isothiocyanate (ANIT). ECM1 and CTGF were also examined in the livers of patients with alcohol-associated liver disease (ALD) or ethanol-exposed animals that were fed the western diet for 4 months in the WDA model with liver pathology resembing ALD in patients. RESULTS: ECM1 bound to CTGF in yeast two-hybrid systems, cultured liver cells, and cholestatic livers damaged by DDC or α-naphthyl-isothiocyanate. This interaction blocked integrin αvβ6-mediated TGFβ activation, thereby reducing fibrotic responses in vitro. ECM1 downregulation was associated with biliary CTGF induction during human ALD progression. In experimental models, Ecm1 loss enhanced susceptibility to DDC-induced cholestasis with upregulation of Ctgf, αvβ6, alpha-smooth muscle actin, procollagen type I, serum transaminase, and total bilirubin levels in germline knockouts, whereas forced expression of this gene significantly attenuated DR and biliary fibrosis after the feeding of DDC or α-naphthyl-isothiocyanate containing diets. Moreover, ectopic Ecm1 inhibited not only alcohol-associated fibrosis but also TGFβ-mediated deregulation of hepatocyte nuclear factor 4α, preventing the production of the fetal p2 promoter-driven isoforms in the WDA model. CONCLUSIONS: We uncover a novel antifibrotic action by ECM1 that binds CTGF and inhibits integrin αvβ6-mediated TGFβ activation. Targeting its loss has therapeutic potential for the treatment of DR and liver fibrosis in chronic conditions, such as cholangiopathy and ALD.