Isolating primary AF cells resulted in cell counts far too low for these in vitro experiments; therefore, Flnb+/+ and Flnb−/− primary sternal chondrocytes were stimulated with 5 ng·mL−1 BMP-2 or 5 ng·mL−1 TGFβ-1. This evidence concerns the gene TGFB1 and atrial fibrillation.