Downregulation of p16 decreases biliary damage and liver fibrosis in the Mdr2-/- mouse model of primary sclerosing cholangitis

Biliary senescence and hepatic fibrosis are hallmarks of cholangiopathies including primary sclerosing cholangitis (PSC). Senescent cholangiocytes display senescence-associated secretory phenotypes (SASPs, e. g., TGF-β1) that further increase biliary senescence (by an autocrine loop) and trigger liver fibrosis by paracrine mechanisms. To determine the effect of p16 inhibition and role of the TGF-β1/miR-34a/SIRT1 axis in biliary damage and liver fibrosis in the Mdr2-/- mouse model of PSC. We treated (i) in vivo male wild-type (WT) and Mdr2-/- mice with p16 Vivo-Morpholino or controls before measuring biliary mass (IBDM) and senescence, biliary SASPs levels and liver fibrosis; and (ii) in vitro intrahepatic murine cholangiocyte lines (IMCLs) with siRNA against p16 before measuring the mRNA expression of proliferation, senescence and fibrosis markers. p16 and miR-34a increased but SIRT1 decreased in Mdr2-/- mice and PSC human liver samples compared to controls. P16 immunoreactivity and biliary senescence and SASPs levels increased in Mdr2-/- mice but decreased in Mdr2-/- mice treated with p16 Vivo-Morpholino. The increase in IBDM and hepatic fibrosis (observed in Mdr2-/- mice) returned to normal values in Mdr2-/- mice treated with p16 Vivo-Morpholino. TGF-β1 immunoreactivity and biliary SASPs levels were higher in Mdr2-/- compared to those of WT mice, but returned to normal values in Mdr2-/- mice treated with p16 Vivo-Morpholino. The expression of fibrosis/senescence markers decreased in cholangiocytes from Mdr2-/- mice treated with p16 Vivo-Morpholino (compared to Mdr2-/- mice) and in IMCLs (after p16 silencing) compared to controls. Modulation of the TGF-β1/miR-34a/SIRT1 axis may be important in the management of PSC phenotype.