MMP9 and persistent truncus arteriosus: The mRNA expression levels of α-SMA, TGF-β, collagen I (Col1), collagen III (Col3), and matrix metalloprotein 9 (MMP9) were increased in the TAC group compared with the sham group (Figures 2C,D), and the mRNA expression levels of TGF-β in the NXK low, middle, high dose groups were significantly decreased vs. the TAC group (p < 0.05 vs. TAC, Figures 2C,D, Supplementary Table S4).