In vivo, the ratio of MMP2/TIMP2 and MMP9/TIMP1 was also elevated in the skin of diabetes mice by qPCR analysis (Supplementary Figure S1) Therefore, MMP-2 and MMP-9 inhibitors were administered to the STZ-induced diabetic mice to evaluate the changes in skin collagen in vivo. The gene discussed is TIMP2; the disease is diabetes mellitus.