MMP1 and polymyositis: Most of the fibrosis-related genes were upregulated, especially Timp1, in dKO mice, and MR16-1 treatment significantly decreased the levels of Timp1. The upregulation of the gene is also found in the skeletal muscle of DMD patients, and an unbalance in matrix metallopeptidase 1 (MMP1)/TIMP metallopeptidase inhibitor 1 (TIMP-1) ratio is a distinguished feature in DMD muscle from dermatomyositis or polymyositis which are rarely developed fibrosis in the skeletal muscle [47].