骨骼肌卫星细胞移植对心肌梗死大鼠心肌纤维化的影响

背景：现已发现心肌梗死后心肌纤维化是心室重构的重要机制，而相关干细胞心肌移植对这一过程的影响报道不多。 目的：观察自体骨骼肌卫星细胞移植对心肌梗死大鼠心肌纤维化的影响，并探讨其可能机制。 设计、时间及地点：随机对照动物实验，于2007-07/09在解放军第三军医大学大坪医院野战外科研究所第三研究室完成。 材料：Wistar大鼠45只，雌雄各半，体质量150~200 g，其中30只用于制备心肌梗死模型。 方法：45只大鼠按随机抽签法分为3组，每组15只。心肌梗死组：结扎冠状动脉左前降支造成心肌梗死，2周后沿梗死区与正常心肌交界处多点注射0.2 mL无血清M199培养液；移植组：造模后将体外培养2周的大鼠自体卫星细胞0.2 mL以注射的方式移植到大鼠梗死区周围。假手术组：不造模，仅在左前降支周围心前壁多点注射0.2 mL生理盐水。 主要观察指标：4周后测定各组大鼠缺血心肌血管内皮生长因子mRNA、血管内皮生长因子蛋白质的表达，缺血心肌毛细血管密度变化，苏木精-伊红染色观察各组心肌细胞在梗死区的生长、增殖情况。 结果：①卫星细胞移植4周后，假手术组和心肌梗死组血管内皮生长因子mRNA和血管内皮生长因子蛋白表达较移植组明显降低(P < 0.01)；心肌梗死组大鼠毛细血管密度较假手术组升高(P < 0.05)；移植组大鼠缺血心肌中毛细血管密度较假手术组、心肌梗死组亦明显升高(P < 0.01)。②苏木精-伊红染色显示假手术组大鼠心肌形态正常，结构清晰，心肌纤维排列整齐有序，肌纤维间无成纤维细胞聚集、增生现象。心肌梗死组大鼠心肌内可见成纤维细胞增生及胶原形成，心肌有序的基本结构发生紊乱。移植组大鼠其梗死区可见较多带有横纹且具有多核的肌细胞存在，组织排列较有序，纤维组织明显少于心肌梗死组。 结论：卫星细胞在心肌梗死区中可增殖分化为具有弹性和收缩功能的横纹肌样细胞，并通过自分泌和旁分泌的形式分泌血管内皮生长因子促使缺血心肌毛细血管增生，从而有效地抑制了缺血心肌的纤维化进程。

Effects of auto-skeletal muscle satellite cell transplantation on myocardial fibrosis in myocardial infarction rats

BACKGROUND: Myocardial fibrosis following myocardial infarction is an important mechanism of ventricle reconstitution. However, there are few reports concerning effects of myocardial transplantation related to stem cells on this process. OBJECTIVE: To investigate the effects of auto-skeletal muscle satellite cells implanted into ischemic myocardium on myocardial fibrosis in rats with myocardial infarction and their mechanisms. DESIGN, TIME AND SETTING: The randomized controlled animal study was performed at the Third Research Room, Research Institute of Surgery, Daping Hospital, Third Military Medical University of Chinese PLA from July to September 2007. MATERIALS: A total of 45 Wistar rats, of both genders, weighing 150-200 g, were used in this study. Of them, 30 rats were used to establish models of myocardial infarction. METHODS: A total of 45 rats were assigned to 3 groups (n = 15). Rats in the myocardial infarction group received ligation of the left anterior descending coronary artery to induce myocardial infarction. 2 weeks later, 0.2 mL serum-free M199 medium was infused into the juncture between infarct region and normal myocardium through multiple points. In the transplantation group, following model induction, 0.2 mL auto-skeletal muscle satellite cells in rats after 2-weeks in vitro culture were transplanted into the surrounding of infarct region. Rats in the sham operation group were not induced to create models, only injected with 0.2 mL saline in the heart anterior wall surrounding the left anterior descending branch through multiple points. MAIN OUTCOME MEASURES: Four weeks after injection, vascular endothelial growth factor mRNA and vascular endothelial growth factor protein expression in the ischemic myocardium was demonstrated. Capillary density changes in the ischemic myocardium were detected. Growth and proliferation of myocardial cells in the infarct region were observed using hematoxylin-eosin staining. RESULTS: Vascular endothelial growth factor mRNA and vascular endothelial growth factor protein expression was significantly decreased in the sham operation and myocardial infarction groups compared with the transplantation group at 4 weeks following satellite cell transplantation (P < 0.01). Capillary density was greater in the myocardial infarction group compared with the sham operation group (P < 0.05). Capillary density was significantly higher in the rat ischemic myocardium in the transplantation group compared with the sham operation and myocardial infarction groups (P < 0.01). Hematoxylin-eosin staining demonstrated that myocardial morphology was normal in rats of the sham operation group, with clear structure, orderly myocardial fibrosis. There were no fibroblast aggregation and hyperplasia among myocardial fibrosis. Fibroblast hyperplasia and collagent formation were found in the rat myocardium in the myocardial infarction group, with disorderly myocardial structure. Myocardial cells with transverse striation and many nuclei were observed in the rat infarct region of the transplantation group, with orderly arrangement. Fibrous tissue was significantly less in the transplantation group compared with the myocardial infarction group. CONCLUSION: Satellite cells can proliferate and differentiate into striated muscle-like cells with flexible and systolic functions in the infarct region. Satellite cells secrete vascular endothelial growth factor and promote blood capillary hyperplasia in ischemic myocardium by autocrine and paracrine, which finally effectively inhibits fibrosis progress in the ischemic myocardium.