SMAD2 and renal fibrosis: Focusing on the role of TGF-β1 expression in renal fibrosis, it was proved that UCG downregulated the protein expressions of TGF-β1, TGF-β receptor I, receptor II and Smad2/3, and upregulated the protein expressions of SnoN and Smad7 (Huang et al., 2014; Wu W. et al., 2016).