Hepatic progenitor cell-originated ductular reactionfacilitates liver fibrosis through activation of hedgehogsignaling

Background: It is poorly understood what cellular types participate in ductular reaction (DR) andwhether DR facilitates recovery from injury or accelerates hepatic fibrosis. The aim of this study is to gaininsights into the role of hepatic progenitor cell (HPC)-originated DR during fibrotic progression.Methods: DR in liver specimens of PBC, chronic HBV infection (CHB) or NAFLD, and four rodentfibrotic models by different pathogenic processes was evaluated. Gli1 expression was inhibited in rodentmodels or cell culture and organoid models by AAV-shGli1 or treating with GANT61.Results: Severity of liver fibrosis was positively correlated with DR extent in patients with PBC, CHB orNAFLD. HPCs were activated, expanded, differentiated into reactive cholangiocytes and constituted“HPC-originated DR”, accompanying with exacerbated fibrosis in rodent models of HPC activation &proliferation (CCl4/2-AAF-treated), Μdr2-/- spontaneous PSC, BDL-cholestatic fibrosis orWD-fed/CCl4-treated NASH-fibrosis. Gli1 expression was significantly increased in enriched pathways invivo and in vitro. Enhanced Gli1 expression was identified in KRT19+-reactive cholangiocytes. SuppressingGli1 expression by administration of AAV-shGli1 or GANT61 ameliorated HPC-originated DR andfibrotic extent. KRT19 expression was reduced after GANT61 treatment in sodium butyrate-stimulated WB-F344 cells or organoids or in cells transduced with Gli1 knockdown lentiviral vectors. In contrast,KRT19 expression was elevated after transducing Gli1 overexpression lentiviral vectors in these cells.Conclusions: During various modes of chronic injury, Gli1 acted as an important mediator of HPCactivation, expansion, differentiation into reactive cholangiocytes that formed DR, and subsequentlyprovoked hepatic fibrogenesis.