Atrial fibrillation (AF) rat models and rat cardiac fibroblasts (CFs) with overexpressed or inhibited miR-10a were used to investigate the possible role of miR-10a-mediated transforming growth factor-β (TGF-β1)/Smads signaling in cardiac fibrosis and fibroblast proliferation in rats with AF. This evidence concerns the gene TGFB1 and fibrosis.