Abstract: Objective To investigate the effect of autologous bone marrow mesenchymal stem cells (MSCs) transplantation on cardiac function and their proliferation and differentiation in the post-infarct myocardium in rabbits. Methods Twenty New Zealand rabbits were randomly divided into two groups, the autologous bone marrow mesenchymal stem cells group (MSCs group,n=10) and control group (n=10). Myocardial infarct model was set up by ligation of the left anterior descending (LAD), two weeks after establishment of the infarct model,either 400μl of cell suspension (total cells 1×106) labled by 1,1’-dioctadecyl3,3,3’,3’-tetramethyl indocarbocyanine perchlorate (Dil) or a comparable volume of L-DMEM medium were autologously transplanted into several different points of the periphery of the scar respectively. To evaluate the heart function, echocardiography were performed before modeling,two weeks after modeling, 2 and 4 weeks after the cells transplantation for asurements of left ventricular end systolic diameter (LVESD) and left ventricular end diastolic diameter (LVEDD), tocalculate left ventricular eject fraction(LVEF) and left ventricular fractional shortening (LVFS). Meanwhile the myocardial contrast echocardiography (MCE) were performed for evaluating the blood perfusion of the post-infarct myocardium. Eight weeks after the transplantation, the animalswere undergoing euthanasia, specimens were acquired for pathology. Results Echocardiography indicated that:The LVEF and LVFS between two groups were fundamentally the same before modeling,two weeks after modeling respectively (0.72±0.08 vs. 0.71±0.04,0.56±0.11 vs. 0.55±0.09; 0.35±0.06 vs. 0.35±0.04, 0.24±0.08 vs. 0.23±0.03, Pgt;0.05), but those were improved significantly in group MSCs when compared with control group at two weeks and four weeks after the cells transplantation(0.71±0.05 vs. 0.60±0.05，0.72±0.07 vs. 0.62±0.08 and 0.34±0.03 vs. 0.29±0.01， 0.35±0.06 vs. 0.27±0.05 respectively,Plt;0.05). There were no differences in LVESD and LVEDD between two groups in any time points(Pgt;0.05). MCE showed the blood perfusion of the infarct myocardium were improved two and four weeks after the cell transplantation. Pathology indicated that Dil positive cells were survived in MSCs transplanted hearts, stained positively for αsarcomeric actin and desmin eight weeks after cell transplantation, HE slides indicated that the capillary density in all the cells transplanted hearts were much higher when compared with control group (38.6±7.6/mm2 vs. 21.4±3.9/mm2，Plt;0.05). ConclusionMSCs can differentiate into cardiomyocytes, improve myocardial perfusion and cardiac function when transplanted into ischemic myocardium.