Research indicates that TGF-β1 modulates renal injury by stimulating downstream Smads, where Smad3 is a key mediator that promotes renal fibrosis, Smad2, and Smad7 have renal protective effects, and Smad4 exhibits both promotion of fibrosis and inhibition of inflammation through different mechanisms (191). Here, SMAD3 is linked to renal fibrosis.