STAT3 and renal fibrosis: Interestingly, unlike PP1 inhibiting Src to block Smad3 and STAT3 signaling pathways [51], Fyn-mediated renal fibrosis is mediated by the non-Smad signaling pathway, that is, caused by activation of STAT3, and Smad3 and AMPK signaling transduction are not essential in this process [61].