Complement factor C5 deficiency significantly delays the progression of biliary fibrosis in bile duct-ligated mice

► C3 is activated during biliary obstruction in both WT and C5-deficient mice. ► C5 significantly attenuates the amount of fibrosis in response upon BDL. ► C5-deficient mice show decreased expression of fibrosis-associated genes and TNF-α. ► Reduced peribiliary infiltration of leucocytes in fibrotic areas with C5 deficiency. ► Decreased expression of MMP-9 and decreased gelatinase activity in C5-deficient mice. Fibrogenesis represents the universal response of the liver to chronic liver injury. Complement factor C5 has been linked to fibrosis in murine toxic liver injury and human chronic hepatitis C. C5 may also play a central role in chronic cholestatic disorders, since the BA receptor FXR has been characterized as an activator of the C3 gene. We aimed to investigate, whether C5 deficiency is able to prevent biliary fibrosis in the mouse bile-duct-ligation model. BDL for 1–4weeks was performed in either Hc0/Hc0 mice (deficient for C5) or WT controls. BA levels were measured by RIA. Histological examination included H&E, sirius-red and immunohistochemistry. mRNA expression was quantified by RT-PCR. Protein expression levels were determined by Western blotting or ELISA. Enzymatic MMP-activity was analysed by zymography. One week BDL leads to fibrosis in WT (F2.0±0), while it is almost absent in Hc0/Hc0 mice (F0.5±0.5). No differences in fibrosis can be detected at week-4. Together with delayed fibrogenesis at week-1, fibrotic markers are decreased in Hc0/Hc0 mice. Expression of the inflammatory cytokine TNF-α is decreased in Hc0/Hc0 mice. In parallel C5 deficiency leads to an attenuated peribiliary infiltration of CD45+ cells in fibrotic areas together with decreased MMP-9 expression and gelatinase activity. The present study proves a functional role of C5 during biliary fibrogenesis. C5 deficiency leads to attenuated inflammation and normalized MMP-9 activity concomitantly with a significant reduction of fibrosis. C5 appears to be an attractive target for future therapeutic intervention in chronic cholestatic liver disease.