Mesenchymal stem cells are pluripotent cells capable of differentiating into myocardial and vascular endothelial cells. The present invention demonstrates that the mesenchymal stem cell sheet have therapeutic potential for a severely damaged heart due to its pluripotency and in situ self-renewal capability. Mesenchymal stem cells derived from adipose tissue were cultured to prepare a mesenchymal stem cell sheet. Four weeks after induction of myocardial infarction in rats, the mesenchymal stem cell sheet was transplanted to the heart. The mesenchymal stem cell sheet were readily engrafted to the surface of the scarred myocardium, grew gradually in situ, and formed a thick layer (approximately 600 μm) in 4 weeks. The grown transplanted mesenchymal tissue contained newly formed blood vessels, myocardial cells, and undifferentiated mesenchymal cells. The engrafted mesenchymal stem cells inhibited thinning of the myocardial wall in the scar area, and improved cardiac function and survival rate in rats with myocardial infarcts. Thus, mesenchymal stem cell sheet transplantation may represent a novel therapeutic approach for myocardial tissue regeneration.
