TGFB1 and atrial fibrillation: In order to test the immediate reaction upon stimulation of monolayer cultivated human AF cells after 24 h, the cells (n = 6; 3 from mild and 3 from degenerated AF tissues) were incubated with human recombinant BMP2 (5 nM), human recombinant TGFβ1 (200 pM), or human recombinant TNFα (10 ng/mL) (Figure 4).