In conclusion, this work clearly indicates that selenium plays a critical role as a ROS scavenger in in vitro expansion of AF-MSCs and long-term maintenance of their multipotency and, when administered together with bFGF, exerts a valuable synergistic effect by inhibiting intracellular ROS accumulation, which otherwise leads to cellular senescence and damage. The gene discussed is FGF2; the disease is atrial fibrillation.