MMP13 and atrial fibrillation: Severely degenerated AF cells cultured in 3D polymer scaffolds showed significant induction of the expression levels of aggrecan (FC = 2.9 at day 21), biglycan (FC = 2.8 at day 21), decorin (FC = 2.2 at day 21), collagen type II (FC = 146.5 at day 21), and MMP13 (up to FC = 21.7 at day 21), compared to severely degenerated AF cells cultured in monolayer.