STAT3 and renal fibrosis: Smad3 is a key downstream factor of TGF-β1, and STAT3 acts downstream of many membrane receptors associated with renal fibrosis, including TGF-b receptors.(Yuan et al., 2022) Immunoblot analysis showed increased expression levels of p-Smad3 and p-STAT3 in the kidney with UUO injury, which was abolished by administration of FT895.