MMP3 and atrial fibrillation: In the present study, degenerative culture conditions combined with TNF-α injection stimulated proinflammatory gene expression (IL-1β, IL-6, and IL-8 in the NP and IL-1β, IL-8, and COX2 in the AF) and upregulated catabolic enzymes (MMP1 and MMP3) with a more profound increase in the NP compared with the AF tissue.