Abstract: Objectives To investigate whether intravenously transplanted human amniotic mesenchymal stem cells (hAMSCs) could improve cardiac function ，and reduce myocardial fibrosis in rats with acute myocardial infarction(MI). Methods The phenotype of hAMSCs was analyzed by flow cytometry (FCM) .MI models were built by left anterior descending artery ligation in male SD rats. The rats were randomly divided into sham operation group, model group and hAMSCs transplanted group, with twelve in each group. At seven days after the MI, 2×106 of BrdU labeled hAMSCs or vehicle (control group) were intravenously administered to rats. At different times after transplantation, echocardiogram, histopathology, immunohistochemistry and immunofluorescence were performed to observe the effects of hAMSCs transplantation on cardiac function ,ventricular remodeling, and histopathologic change , as well as the survival and differentiation of the transplanted cells in the MI regions. Results ①The hAMSCs group showed a significant improvement in ejection fraction and left ventriccular fractinal shortening compared with those in the model group at 1w, 4w and 6w after transplantatio. In this group there were also a significant increase in left ventricular anterolateral wall thickness at diastole and left ventricular anterolateral wall thickness at systole.②Six weeks after hAMSCs transplantation, the percentage of fibrosis area was decreased singnifcantly compared with the model group.③the cardiac-specific protein connexin -43, α-actinin and desmin positive cells were detected in BrdU-labeled cells.Conclusion Intravenous transplantation of hAMSCs can improve cardiac function and myocardial fibrosis after MI , and transplanted hAMSCs may differentiate into cardiomyocytes in the myocardial infarction zone.

Key words: human amniotic mesenchymal stem cells, myocardial infarction, transplantation, differentiation, cardiac function