Background: Cell therapy using mesenchymal stem cell (MSC) to ischemic heart diseases is in fast progress. Besides of bone marrow, umbilical cord blood (UCB) or adipose tissue are recently interested as a source of MSC thanks to their easy accessibility. We elucidated whether human UCB and adipose tissue derived MSCs survive and engraft in experimentally induced ischemic rat myocardium. Materials and Methods: MSCs were isolated and characterized from human UCB and adipose tissue. Myocardial infarction was induced by ligation of left anterior descending coronary artery (LAD) in 150-200 g weighing Sprague-Dawley rats. One week after LAD ligation, 1 to 5 x 10⁶ adult human MSCs were injected around the infarcted area using a 30G needle. Before and 4 weeks after surgery, the echocardiograph was performed and the hearts were excised for further analysis. Histological studies were performed by H&E staining, immunohistochemisty, and in situ hybridization using human specific probe in time course. Results: Even though the induction of xenoreactivity was observed, in situ hybridization revealed transplanted human-derived MSCs were engrafted in rat myocardium 4 weeks after injection. H&E staining showed fibrosis was decreased in MSC-treated infarcted myocardium compared with control one. In echocardiograph findings, fractional shortening (FS) was 43.1% and 50%, and ejection fraction (EF) was 79.3% and 85.7% in UCB and adipose tissue derived MSCs injected rats, respectively (control FS; 17.2%, and control EF; 40.6%). Conclusions: Both UCB and adipose tissue derived MSCs are another candidate for improvement of the left ventricular function by durable myogenic process in myocardial infarcted rats. In detailed analysis including immunohistochemical findings in time course will be presented in the autumn meeting.