MMP13 and atrial fibrillation: Treatment with IL-1β at 1.0 ng/ml significantly upregulated the expression levels of IL-1β, MMP-3, and MMP-13 by both AF and NP cells (relative expression: ahRANKL-mAB 0 μg/ml + IL-1β (vs. control): AF: IL-1β 136.72 ± 34.42; MMP-3 684.99 ± 335.81; MMP-13 92.98 ± 28.04; p < 0.01, respectively, NP: IL-1β 9647.31 ± 7213.02, p < 0.05; MMP-3 971.23 ± 336.88, p < 0.01; MMP-13 29.17 ± 8.46, p < 0.01) (Fig. 6a-f).