Objective To study the effect of contusion and exhaustive exercise on satellite cells' activation and Pax7/CBF1/DAPT contents in skeletal muscles of rats,and reveal the repair mechanism of the skeletal muscle injury.Methods Twenty-four seven-week-old male Sprague-Dawley(SD)rats were randomly divided into a control(C)group,an immediately after exhaustive exercise(E0)group,a 24 hours after exhaustive exercise(E24)group and a 48 hours after exhaustive exercise(E48)group,each of 6.Other 18 SD rats were randomly divided into 3 groups,6 rats in each group:an immediately after contusion group(D0),a 24h post-contusion group(D24)and a 48h post-contusion group(D48).All groups were killed at different time points after exhaustive exercise and the contusion respectively while the control group was at resting state,and their serum was extracted.The right gastrocnemius muscles were resected and divided into 2 parts:one was used immediately for culturing satellite cells,while the other was stored in the bridge at-80℃.All the serum and gastrocnemius muscles were tested for Pax7,CBF1 and DAPT contents using the enzyme-linked immunosorbent assay(ELISA).Moreover,three-day-old newborn rats were also slaughtered for the above experiment.Results The results of culture in vitro showed that one day after the culture began a small amount of spindle satellite cells could be seen in the newborn rats,but the satellite cells of other groups were growing slowly.However,on the third day and the fifth day,the spindle satellite cells of each group began to proliferate in quantity and reached the peak.Then all the satellite cells had a good proliferation until the seventh day after serial passage,and some patial fusions to microtubules occurred.The biggest cell number and proliferation rate was in newborn rats,but no skeletal muscle satellite cell was found in the control group.At the same time,the number and the proliferation rate of skeletal muscle satellite cells in contusion groups were significantly higher than the exhaustive exercise groups.The results of Elisa showed that the contents of CBF1 and Pax7 in skeletal muscles in exhaustive groups and contusion groups,were significantly upregulated,compared to the control group(P＜0.05).Amomg them,the CBF1 content in group D0,together with the Pax7 content in group D24 and D48,was significantly higher than that of the other groups(P＜0.05).On the other hand,the content of DAPT in skeletal muscles of exhaustive groups and contusion groups,compared to the control group,was significantly downregulated (P＜0.05).To be more specific,the value of group D0 was significantly lower than that of the other groups (P＜0.05).However,there was no significant difference in it among group E0,E24 and E48.Conclusions Contusion and exhaustive exercise can activate the skeletal muscle satellite cells to proliferate and differentiate.The number of activated skeletal muscle satellite cells in the contusion groups is significantly larger than that of exhaustive groups maybe due to the stronger stimulating by contusion.Both contusion and exhaustive exercise increase the contents of Pax7 and CBF1 in skeletal muscles,but decrease that of DAPT.The Pax7 and CBF1 may play a positive regulating role in terms of activating skeletal satellite cells and repairing skeletal muscle injury,while DAPT may play a negative regulating role.%目的:研究钝挫伤及力竭运动对大鼠骨骼肌卫星细胞激活及Pax7/CBF1/DAPT含量的影响,探索损伤修复的机制.方法:取7周龄雄性SD大鼠24只,分为4组,每组6只:安静对照组(C组);力竭运动即刻组(E0组);力竭运动后24 h组(E24组);力竭运动后48 h组(E48组).另取18只SD大鼠,分为3组,每组6只:钝挫伤即刻组(Do组);钝挫伤后24 h组(D24组);钝挫伤后48 h组(D48组).各组分别于安静状态、力竭运动后和钝挫伤后不同时间点,宰杀取血,分离血清.并取下右侧腓肠肌,将腓肠肌分为二份,一份立即进行细胞培养实验,另一份和血清一起在-80℃冰箱保存,用ELISA法检测Pax7、CBF1、DAPT的含量变化.另取新生3日龄鼠3只,宰杀后同样取右侧腓肠肌进行细胞培养实验.结果:(1)体外培养结果显示:新生鼠1天后即可见到梭形卫星细胞,其它各组的肌卫星细胞增长速度较慢,到第3天、第5天时各组开始大量增殖梭形细胞,且一直保持增殖良好并传代,第7天仍有较好的长势,且出现部分融合和微管.各组比较显示,安静对照组未见卫星细胞增殖;新生鼠卫星细胞数量最高,增殖速度也最快;而钝挫伤组的肌卫星细胞数量及增殖速度显著高于力竭运动组.(2)ELISA结果显示:力竭运动组和钝挫伤组各组骨骼肌、血清中CBF1和Pax7的含量与安静对照组相比均显著上调(P＜0.05),其中D0组的CBF1含量差异极显著(P＜0.01),明显高于其他各组(P＜0.05);D24、D48两组的Pax7含量亦明显高于其他各组(P＜0.05).而DAPT在各组骨骼肌、血清中的含量与安静对照组相比均显著下调(P＜0.05),其中D0组DAPT差异极显著(P＜0.01)且明显低于其他各组(P＜0.05).但力竭运动各组(E0、E24、E48)之间无显著性差异.结论:(1)钝挫伤及力竭运动可使肌卫星细胞激活、增殖分化,并且钝挫伤导致的肌卫星细胞的激活数量明显高于力竭运动组,可能由于钝挫伤的刺激更强所致.(2)钝挫伤和力竭运动可以使大鼠骨骼肌和血清Pax7和CBF1的含量上升,但下调DAPT的含量.Pax7和CBF1可能在骨骼肌卫星细胞激活及骨骼肌损伤修复中起着正向调节的作用,而DAPT可能起着负向调节作用.
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