SMAD2 and atrial fibrillation: The inhibition of TGFβ significantly deters TF-induced expression of SMA and collagens by attenuating the phosphorylation of Smad2.635 The cyclic strain of fibroblasts was shown to elevate ECM deposition (i.e., collagens and fibronectin) via protein kinase C and tyrosine kinase signaling.636,637 In addition, ERK1/2 and NF-κB signaling also respond to the cyclic strain on cardiac fibroblasts.638,639 Besides, atrial fibrillation (AF)-associated with abnormal atrial stretch is also a factor contributing to cardiac fibrosis.