PPARγ inactivates the TGF-β1/Smad2/3 signaling pathway and suppresses expression of OA-related genes in chondrocytes. Normal chondrocytes were used as controls and OA chondrocytes were treated with or without DMSO, GW1929, GW1929 + PBS or GW1929 + TGF-β1. A, Expression of TGF-β1, Smad2, and Smad3, along with the extent of Smad2 and Smad3 phosphorylation in chondrocytes evaluated by Western blot analysis normalized to GAPDH. B, Expression of MMP-13, ADAMTS-4, ADAMTS-5, HtrA1, iNOS, and Collagen II in chondrocytes evaluated by Western blot analysis normalized to GAPDH. C, The levels of IL-6, IL-1β, TNF-α, and COX-2 in chondrocytes detected by ELISA. The experiment was repeated three times. ∗p < 0.05 vs. control chondrocytes; #p < 0.05 vs. OA chondrocytes treated with DMSO; & p < 0.05 vs. OA chondrocytes treated with GW1929 + PBS.