Utrastructural changes of the infracted myocardium after mesenchymal stem cells transplantation

Objective To observe the ultrastructural changes of the infarcted myocardium after mesenchymal stem cells (MSCs) transplantation so as to investigate the underlying mechanisms of MSCs transplantation for myocardial infarction. Method MSCs labeled with bromodeoxyuridine(BrdU) were injected into the infarcted myocardium at 1~2 h after ligating the left anterior descending(LAD) coronary artery . 6 weeks after transplantation, MSCs surviving in infarcted myocardium were identified by Immunohistochemistry. Ultrastructural changes were observed by electron microscope. Result BrdU-positive cells were seen in the infarcted myocardium in MSCs group but not in AMI group. In MSCs group, some immature cells that form partly gap junction with normal myocardium were seen on the periphery of infarcted area with a big nucelus-to-cytoplasm ratio, small sarcomere and dissimilarly developed myofibril. Compared with the MSCs group, mitochondria swelling with decreasing crista and black grains like floccular process, cardiac muscle fibers breakage and fibrosis were more severe in the MI group. Conclusion MSCs transplantation can relieve myocardial cell necrosis and MSCs potentially differentiate into cadiocyte-like cell.