Abstract： Objective To determine the effects of BMSCs transplantation on ventricular remodeling and FSTL1 expression in myocardial tissues of rats with myocardial ischemia?reperfusion. Methods Fifteen SPF SD rats aged 4 weeks old and weighing 90?100 g were included for BMSCs preparation. Forty?five SD rats weighing 200?250 g were included for the establishment of myocardial ischemia?reperfusion rat model. All the rats were randomly divided into sham operation group,model group and BMSCs transplantation group(n=15 each). The model group and BMSCs transplantation group underwent thoracotomy to block the coronary artery to further construct a myocardial ischemia?reperfusion model after recanalization,and the sham operation group underwent thoracotomy alone. BMSCs transplantation group was injected with BMSCs fluid by a micro?syringe at the junction of myocardial infarction and normal tissues. Model group and sham operation group were injected with the same volume of cell culture medium. The two groups were fed for continuous 14 d after the thoracic cavity was sutured. After the feeding,the rats in each group were anesthetized,and the right carotid artery was separated to determine the hemodynamic parameters. The rats were sacrificed,and the blood and heart tissues were collected. The LDH and CK levels in serum and MDA and SOD levels in myocardial tissues were examined. The ventricular remodeling was determined by HE staining. The apoptosis of cardiomyocytes was determined by Tunel staining. The protein expression level in myocardial tissues in each group was analyzed by Western blotting. Results The hemodynamic analysis in each group showed that there was no difference in heart rate between the groups(P>0.05). Compared with the model group,the SBP,DBP and LVSP in the BMSCs transplantation group increased significantly,whereas the LVEDP somehow decreased(all P<0.05). At the same time,the LDH and CK levels in serum and MDA level in myocardial tissues in the BMSCs group significantly decreased,whereas the SOD level in myocardial tissues significantly increased(all P<0.05). In terms of ventricular remodeling,the left ventricular wall thickness of infarct region and ratio of septum thickness/left ventricular free wall thickness(SPT/LVWT)in myocardial tissues in the BMSCs transplantation group were somehow improved,whereas the SPT and myocardial across area of septum(MAAS)and infarct area decreased significantly compared with those in the model group(all P<0.05). Western blot showed that the expression levels of FSTL1 and Bcl?2 in myocardial tissues in the BMSCs transplantation group significantly increased,whereas the expression levels of pro?apoptotic proteins Bad and cleaved?caspase?3 significantly decreased compared with those in the model group (P<0.05). Conclusion BMSCs transplantation may promote the FSTL1 expression in myocardial tissues,decrease the apoptosis of cardiomyocytes and promote ventricular remodeling in rats with myocardial ischemia?reperfusion.