Matricellular Signaling in Hepatobiliary Injury Repair

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 DESCRIPTION (provided by applicant): Liver fibrosis is the excessive accumulation of extracellular matrix as a wound healing response to chronic injuries from a broad range of liver diseases, irrespective of the underlying etiology. Advanced liver fibrosis may lead to cirrhosis, liver failure, and neoplasia. Extracellular matrix deposition is crucial to wound healing by promoting tissue formation and integrity, but commonly becomes uncontrolled in chronic injuries and leads to fibrosis. Ductular reaction is part of the injury response in the liver occurring at te interphase of the parenchymal and portal compartments that promotes bile duct regeneration. Although prominent in response to biliary and cholestatic damages, ductular reaction is observed in virtually all chronic human liver diseases. Recent studies have revealed that the matricellular protein CCN1 induces cholangiocyte proliferation and ductular reaction in response to cholestatic injuries through integrin v5-mediated activation of NFB, leading to Jag1 expression and Jag1/Notch signaling. Furthermore, CCN1 is able to restrict and resolve liver fibrosis induced by either hepatotoxin (carbon tetrachloride) or cholestasis (bile duct ligation) b inducing cellular senescence in myofibroblasts derived from hepatic stellate cells and portal fibroblasts. CCN1 also appears to regulate myofibroblast activation and resolution of inflammation. Based on these observations, we hypothesize that CCN1 serves multiple functions in different stages of hepatobiliary injury repair through binding distinct integrins in different cell types. We will scrutinize this hypothesis in three specific aims: (1) to conduct genetic and functional analyses of the heretofore unexplored CCN1-v5-NFB axis in ductular reaction; (2) to examine how CCN1 induces the reactive cholangiocyte phenotype and differentiation of hepatic progenitor cells in the ductular reaction niche; and (3) to investigate how CCN1 regulates the initiation and termination of fibrogenesis in injury repair. These studies will elucidate the diverse roles of CCN1 as a critical regulator of injury repair in chronic liver diseases, and may lead to new therapeutic targets and treatment strategies for the prevention and treatment of liver fibrosis.