MMP2 and atrial fibrillation: 3D assembly of expanded AF cells derived from slightly degenerated annulus fibrosus tissue in polymer scaffolds resulted in significant induction (p < 0.05) of the expression levels of aggrecan (up to FC = 7.8 at day 21), decorin (up to FC = 6.5 at day 21), collagen type II (FC = 83.4 at day 21), MMP2 (up to FC = 6.4 at day 21), and MMP13 (FC = 89.4 at day 7 and FC = 47.2 at day 21), compared to the expression levels found in expanded AF cells in monolayer from slightly degenerated tissue.