SMAD3 and renal fibrosis: In addition to the NF‐κB pathway, transforming growth factor (TGF)‐β1—the central pathogenic mediator of renal fibrosis—acts via a well‐known canonical pathway that phosphorylates and activates Smad2 and Smad3 by combining with the TGF‐β receptor 1.13, 14, 15