SMAD4 and infection: Alpha-smooth muscle actin (α-SMA), collagen I, collagen III, TGF-β1, Smad2, Smad3, and Smad4 showed a significant increase in mitochondrial RNA (mRNA) and protein expression compared with the control group at 7 and 9 weeks post-infection (wpi), while an opposite effect on Smad7 was observed.