Moreover, Kaleta et al.39 demonstrated that sildenafil downregulates OPN gene expression in human peripheral mononuclear cells; that secret OPN during chronic liver injury as patients with primary biliary cirrhosis, autoimmune hepatitis, hepatic cirrhosis, and primary sclerosing cholangitis have all been shown to have elevated hepatic OPN levels. Here, SPP1 is linked to sclerosing cholangitis.