MMP9 and fibrosis: MiR-21 expression was shown to be positively connected with ACR and the glomerular fibrosis index (GSI), but negatively correlated with Ccr. MiR-21 has a role in the DN process, which promotes urinary protein excretion and exacerbates renal function impairment. By modulating the production of TIMP-1 and MMP-9 in DN, miR-21 promotes ECM deposition.