SMAD7 and kidney disorder: In recent years, studies have determined that Smurf2 expression is increased in kidney disease models, for example, Smurf2 and TGF-β protein expression is increased after 7 days in the unilateral ureteral obstruction kidney, but expression is then decreased by the UPP inhibitor, MG132; at the same time, Smad7 expression is increased and fibrous degeneration is improved [29].