SMAD2 and atrial fibrillation: Moreover, the short-term bleomycin could induce BMSCs towards a stronger fibroblast phenotype, although with long-term usage it might cause the cells to undergo aging (in some studies, the senescence of BMSCs or other cells was found to be associated with the transition into fibrotic phenotype [39, 40]), and for fibroblastic-like cell AF cells, it could promote the migration and collagen deposition via the TGFβ-TGFβR1-SMAD2/3 signaling pathway.