SMAD3 and atrial fibrillation: Eight, randomly selected genes (TGF-β2, SMAD3 [10, 11], COL1A1, COL1A2, COL1A3 [12], PARP1 [13], INHBA [14] and NR4A1 [15] from the categories of AF-related genes of the microarray were validated at corresponding protein level by immunohistochemistry (IHC).