Although the beneficial effects of collagenolytic MMPs such as MMP‐1 and MMP‐8 on liver fibrosis have been documented 38, 39 previous study on a model of the biliary duct ligation‐induced cholestasis and fibrosis using MMP‐13 KO mice showed a promotional effect of MMP‐13 on the initial inflammatory response and subsequent fibrosis 29. The gene discussed is MMP1; the disease is cholestasis.