In addition, "in vitro" and animal studies have shown that renal fibrosis is positively correlated with the expression and activation of MMPs, and urine MMP-1, -2, -9 excretion and the urine MMP-1, -2, -9/TIMP–1 ratio can be used as early biomarkers of renal fibrosis (Ahmed et al., 2007; Hirt-Minkowski et al., 2014; Bieniaś and Sikora, 2018). The gene discussed is MMP1; the disease is renal fibrosis.