目的 观察大鼠急性心肌梗死后心肌干细胞在梗死病程中的动态变化。 方法 成年SD大鼠50只，结扎冠状动脉前降支制备急性心肌梗死模型，在术前及术后1周、2周、3周和4周分别检测心功能指标：左室射血分数（LVEF）、左室短轴缩短率(LVFS)、左室舒张末期内径(LVEDD)、左室舒张末期容积(LVEDV)和左室后壁舒张末期厚度（LVPWT）。取各组大鼠新鲜心脏，石蜡切片、Masson染色，确定心肌梗死的病理变化。利用免疫组织化学技术对各组心脏切片进行免疫染色，观察干细胞抗原-1(Sca-1)、Nanog阳性心肌干细胞的动态变化。对每组切片阳性表达的细胞数进行定量分析。利用Western blotting技术观察Sca-1、Nanog的蛋白含量。 结果 大鼠心功能于术后1周开始降低，自第3周稳定于较低水平；Masson染色显示心肌梗死区域瘢痕组织明显，证实模型制备成功；免疫组织化学结果显示，Sca-1、Nanog阳性心肌干细胞数量在2周时上升至高峰，随后下降。 结论 Sca-1、Nanog阳性心肌干细胞在心肌梗死病理演变过程中呈先上升后下降的趋势，提示心肌干细胞在心肌损伤和修复过程中发挥了重要作用。

Objective To explore the significance of the dynamic changes of cardiac stem cells after the acute myocardial infarction in rats. Methods The anterior descending coronary artery of 50 healthy adult SD rats was ligated to prepare an acute myocardial infarction model. Cardiac function indicators, including the left ventricular ejection fraction (LVEF), left ventricular shortening fraction(LVFS), left ventricular end-diastolic diameter (LVEDD), left ventricular end-diastolic volume (LVEDV) and diastolic left ventricular posterior wall thickness (LVPWT) were detected by echocardiography preoperatively and 1 week, 2 weeks, 3 weeks and 4 weeks postoperatively. The hearts of each group of rats were collected. Paraffin sections were stained with Masson to determine the pathological changes of myocardial infarction. The heart slices of all groups were immune-colored by using immunohistochemical technique and the dynamic changes in stem cell antigen-1（Sca-1）⁺ and Nanog⁺ myocardial stem cells were observed. The number of cells expressed in each group were quantitatively analyzed. The protein content of Sca-1 and Nanog was observed by Western blotting. Results The rat cardiac function began to reduce 1 week after the operation, and maintained at a relatively lower level 3 weeks later. Masson staining showed obvious scar tissue in myocardial infarction area, which confirmed the success of model preparation. The immunohistochemical result showed that the Sca-1 and Nanog positive cardiac stem cells number rose to a peak at 2 weeks and decreased afterwards. Conclusion Sca-1 and Nanog positive cardiac stem cells showed a tendency to rise first and then decrease during the pathological changes of myocardial infarction, suggesting that myocardial stem cells may play an important role in myocardial injury and repair. Masson to determine the pathological changes of myocardial infarction. The heart slices of all groups were immune-colored by using immunohistochemical technique and then the dynamic changes in stem cell antigen-1（Sca-1）⁺ and Nanog⁺ myocardial stem cells were observed. The number of cells expressed in each group was quantitatively analyzed. The protein content of Sca1 and Nanog was observed by Western blotting.  Results The rat cardiac function began to reduce 1 week after the operation, and maintained at a relatively lower level 3weeks later; Masson staining showed obvious scar tissue in myocardial infarction area, which confirmed the success of model preparation; The immunohistochemicalresult showed that the Sca1 and Nanog positive cardiac stem cells number rose to a peak at 2 weeks and decreased afterwards.  Conclusion Sca1 and Nanog positive cardiac stem cells showed a tendency to rise first and then decrease during the pathological changes of myocardial infarction, Suggesting that myocardial stem cells play an important role in myocardial injury and repair.