Tehran University of Medical Sciences The Research in Heart Yield and Translational Medicine (RHYTHM) 3115-7270 12 2 2017 05 15 65 71 EN Shahram Rabbani Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran Masoud Soleimani Tarbiat Modares University, Tehran, Iran. Mohammad Sahebjam Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. Mohammad Imani Iran Polymer and Petrochemical Institute, Tehran, Iran. Seyed Mahdi Nassiri Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. Amir Atashi Stem Cell and Tissue Engineering Research Center, Shahroud University of Medical Sciences, Shahroud, Iran. Morteza Daliri Joupari National Institute for Genetic Engineering and Biotechnology, Tehran, Iran. Ali Ghiaseddin Tarbiat Modares University, Tehran, Iran. Payman Latifpour Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. Seyed Hossein Ahmadi Tafti Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. 2016 11 02 2017 02 09 Background: Myocardial infarction is the main cause of death worldwide. Angiogenesis, a promising new therapy for the treatment of diffuse coronary artery disease, shows a poor response to conventional revascularization techniques. This study focused on improving myocardial function using endothelial cells (ECs) and mesenchymal stem cells (MSCs) in a sheep animal model. Methods: Acute myocardial infarction was induced in 18 sheep (12 treated cases and 6 controls). Autologous MSCs and ECs were injected in the infarcted area and the border zone. Two months after transplantation, echocardiography, electron microscopy, and immunohistochemistry were performed. Results: Echocardiography in both MSC and EC groups revealed a significant improvement in the ejection fraction compared with the control group (p value < 0.05). Vascular density, estimated by antibodies against the von Willebrand factor and smooth muscle actin, increased in both study groups. The pattern of vascularity in the MSC and EC groups was diffused. The electron microscopic evaluation of the infracted areas revealed cardiomyocytes in variable stages of development in the border zone in both EC and MSC groups. Conclusion: Both ECs and MSCs were able to promote angiogenesis and improve cardiac function. Presumably, MSCs differentiate into ECs and cause angiogenesis as it occurs for ECs. https://rhythm.tums.ac.ir/index.php/jthc/article/view/624 https://rhythm.tums.ac.ir/index.php/jthc/article/download/624/587