8周运动预适应增强脂肪干细胞治疗心肌梗死大鼠的效果

Exercise preconditioning for eight weeks enhances therapeutic effect of adipose-derived stem cells in rats with myocardial infarction

背景:干细胞移植是心肌梗死的崭新疗法,然而梗死区域极其恶劣的微环境造成干细胞存活率低下并导致远期疗效甚微。运动预适应是一种通过运动诱导机体产生内源性保护效应的方式,可作为心脏康复预防与治疗的新策略。目的:评估运动预适应是否能够增强大鼠心肌梗死后脂肪干细胞移植的心脏保护效应,探讨血管生成在其中的作用机制。方法:6周龄雄性SD大鼠随机分为对照组、造模组、干细胞组以及干细胞运动组。利用冠状动脉闭塞术制作急性心肌梗死模型,对照组同期行假手术;干细胞运动组于造模前进行8周有氧运动,造模后30 min进行脂肪干细胞移植;干细胞组仅进行脂肪干细胞移植。干细胞移植后1 d和7 d,利用免疫印迹法测定心肌总Akt(t-Akt)、磷酸化Akt(p-Akt)、血管内皮生长因子(VEGF)、总内皮型一氧化氮合酶(t-eNOS)和磷酸化内皮型一氧化氮合酶(p-eNOS)蛋白表达量,计算p-Akt/t-Akt和p-eNOS/t-eNOS比值;4周后利用彩色多普勒超声诊断系统检测心脏结构与功能以及心肌血流量,TTC染色法检测心肌梗死面积,Masson染色法检测心肌间质胶原沉积,免疫荧光染色法测定心肌毛细血管密度,TUNEL染色法评估心肌细胞凋亡。结果与结论:(1)干细胞移植后4周:与对照组比较,造模组左心室缩短分数、左心室射血分数、心肌毛细血管密度和心肌血流量下降(P<0.05),心肌梗死面积、胶原容积分数和细胞凋亡增加(P<0.05);与造模组比较,干细胞组上述指标(除左心室缩短分数和左心室射血分数外)得到改善(P<0.05);与干细胞组比较,干细胞运动组以上各参数进一步改善(P<0.05)。(2)干细胞移植后1 d:与对照组比较,造模组t-Akt、p-Akt、VEGF、t-eNOS、p-eNOS蛋白表达量以及p-Akt/t-Akt、p-eNOS/t-eNOS比值均无显著性变化(P>0.05);与造模组比较,干细胞组上述指标均无显著性变化(P>0.05),干细胞运动组磷酸化p-Akt蛋白表达量以及p-Akt/t-Akt比值上调(P<0.05)。(3)干细胞移植后7 d:与对照组比较,造模组p-Akt、VEGF、p-eNOS蛋白表达量以及p-Akt/t-Akt、p-eNOS/t-eNOS比值下降(P<0.05);与造模组比较,干细胞组各参数均无显著性变化(P>0.05),干细胞运动组p-Akt、VEGF、p-eNOS蛋白表达量以及p-Akt/t-Akt、p-eNOS/t-eNOS比值升高(P<0.05)。结果表明:运动预适应可增强脂肪干细胞对心肌梗死大鼠心脏重塑的治疗效果,其机制与促进心肌血管生成并增加血流灌注有关。

BACKGROUND:Stem cell transplantation is a novel therapy for myocardial infarction,but the extremely hostile microenvironment in the infarct area results in low survival rate of stem cells and little long-term effect.Exercise preconditioning is a way to induce endogenous protective effects through exercise,which can be used as a new strategy for prevention and treatment of cardiac rehabilitation.OBJECTIVE:To evaluate whether exercise preconditioning potentiates the cardioprotective effects of adipose-derived stem cell transplantation following myocardial infarction in rats and to explore the mechanism of angiogenesis.METHODS:Six-week-old male SD rats were randomly divided into control group,modeling group,stem cell group,and stem cell plus exercise group.Acute myocardial infarction model was made by coronary artery occlusion,and sham operation was performed in control group.The stem cell plus exercise group underwent aerobic exercise for 8 weeks before modeling,and adipose-derived stem cell transplantation was performed 30 minutes after modeling.The stem cell group performed only adipose-derived stem cell transplantation.One and seven days after stem cell transplantation,the expression levels of myocardial total Akt(t-Akt),phosphorylated Akt(p-Akt),vascular endothelial growth factor(VEGF),total endothelial nitric oxide synthase(t-eNOS),and phosphorylated endothelial nitric oxide synthase(p-eNOS)protein were measured by western blotting,and the ratios of p-Akt/t-Akt and p-eNOS/t-eNOS were calculated.At 4weeks after stem cell transplantation,the heart structure and function as well as myocardial blood flow were detected by color Doppler ultrasound diagnostic system.Myocardial infarction area was measured by TTC staining.Myocardial interstitial collagen deposition was examined by Masson staining.Myocardial capillary density was detected by immunofluorescence staining,and myocardial apoptosis was measured by TUNEL staining.RESULTS AND CONCLUSION:(1)Four weeks after stem cell transplantation:Compared with control group,left ventricular shortening fraction,left ventricular ejection fraction,myocardial capillary density,and myocardial blood flow decreased(P<0.05),myocardial infarction area,collagen volume fraction,and apoptosis increased(P<0.05)in the modeling group.Compared with the modeling group,the above indexes(except for left ventricular fractional shortening and left ventricular ejection fraction)in the stem cell group improved(P<0.05).Compared with the stem cell group,the above parameters were further improved in the stem cell plus exercise group(P<0.05).(2)One day after stem cell transplantation:Compared with the control group,the protein expression of t-Akt,p-Akt,VEGF,t-eNOS,p-eNOS and the ratio of p-Akt/t-Akt and p-eNOS/t-eNOS had no significant changes in the modeling group(P>0.05).Compared with the modeling group,there were no significant changes in the above indexes in the stem cell group(P>0.05),and p-Akt protein expression and the ratio of p-Akt/t-Akt were up-regulated in the stem cell plus exercise group(P<0.05).(3)Seven days after stem cell transplantation:Compared with the control group,the protein expression of p-Akt,VEGF,p-eNOS and the ratio of p-Akt/t-Akt and p-eNOS/t-eNOS were decreased in the modeling group(P<0.05).Compared with the modeling group,there were no significant changes in all parameters in the stem cell group(P>0.05),and the protein expression of p-Akt,VEGF p-eNOS and the ratio of p-Akt/t-Akt and p-eNOS/t-eNOS were increased in the stem cell plus exercise group(P<0.05).These findings confirm that exercise preconditioning can potentiate the therapeutic effect of adipose-derived stem cells on cardiac remodeling in rats with myocardial infarction,and its mechanism is associated with the promotion of myocardial angiogenesis and blood perfusion.