DDR1 and primary biliary cholangitis: DDR1a mRNA expression is significant increased in cirrhotic livers with PBC and HCV. DDR1 protein is strongly expressed in cirrhotic liver parenchymal cells and bile ductule epithelial cells. The ectodomain of DDR1 is shed more easily in cirrhotic liver than in the non-diseased liver. Huh7 cells overexpressing DDR1 exhibit enhanced specific adhesion to collagen type I and contribute to MMP activation