SMAD2 and atrial fibrillation: As correspondingly activated by TGF-β, VEGF, and IL-6 in the CM of AF-MSCs treated with bFGF and selenium, the total protein and phosphorylation levels of Smad2, AKT-MEK1/2-ERK, and NFκB were investigated as the signaling molecules involved in the migration of dermal fibroblasts cultured in AF-MSC-CMs (Fig. 7).