SMAD2 and renal fibrosis: MSCs could reduce tubular EMT and renal fibrosis by decreasing levels of IL-6, IL-1β, TNF-α, TGF-β, PAI-1, ICAM-1, α-SMA, collagen I, collagen IV, FN, caspase 3, PCNA, tubular CCL-2, CCL-5, MMP3, MMP-9, TIMP1, FasL, α-1-antitrypsinin, phosphorylated Smad2, Smad3, NF-κB expression, and p38 MAPK signaling.