SMAD3 and diabetes mellitus: MiR-21 modulates p-Smad3 (Ser423/425), EMT, and ECM deposition via Smad7 regulation under high glucose and diabetes circumstances. In vitro and in vivo, BMP-7 is implicated in the antifibrotic process in DN through modulating miR-21/Smad7 and influencing TGF-β1/Smad3 signaling.