SMAD3 and sarcopenia: In mice with sarcopenia, losartan restored the necessary downregulation of Pax7 and MyoD and upregulation of p21 and myogenin, which are required for successful completion of regeneration of injured muscle, by modulating TGF-β signaling both via Smad2/Smad3 phosphorylation and via activation of MAPKs[6,13].