SMAD3 and polycystic ovary syndrome: In the PCOS group, the protein levels of TGF-β1, TGF-βR1, p-Smad2, p-Smad3, Smad4, α-SMA, collagen I, and CTGF were markedly increased, while Smad7 was notably decreased, indicating the activation of the TGF-β1/Smad signaling pathway (Figures 8 and 9).