MMP13 and atrial fibrillation: Moreover, downregulation of collagen I (p < 0.05), upregulation of collagen II of AF in Group B, C, D, and E, and with the exception of group A(all p < 0.05), but did not show a significant effect on gene expression levels of aggrecan, MMP3, MMP13, and ADAMTs-4 of AF in Group A, B, C, D, and E (p > 0.05) (Fig. 5B(A-F)).