离心运动引起骨骼肌过度使用损伤机理研究

目的:探讨长期离心运动引起骨骼肌过度使用损伤的发生机制。方法:12只雄性SD大鼠随机分成安静对照组(C组)和训练组(TG组)两组。训练组采用4周低强度跑台离心运动(-16°、60-90分/天,5天/周)建立过度使用损伤动物模型。第4周取股中间肌,采用透射电子显微镜观察骨骼肌细胞超微结构损伤累积;采用扫描电子显微镜观察骨骼肌神经、血管结构损伤和胶原纤维结构变化;采用Masson氏三色染色法评价骨骼肌组织的胶原纤维沉积量;采用免疫组化方法量化沉积的胶原纤维中的collagenⅠ表达,并依据collagenⅣ染色,观察肌细胞的基质膜形态变化。结果:⑴骨骼肌超微结构变化:与安静对照组比较,训练组骨骼肌超微结构异常变化,体现为Z线流、肌原纤维间隙变宽、肌原纤维降解、肌膜下线粒体聚积和肌原纤维内线粒体降解物堆积;⑵肌膜结构变化:训练组肌膜结构完整,没有撕裂现象;⑶骨骼肌神经和血管结构变化:与安静对照组比较,TG组神经和血管结构损伤,且collagenⅠ过度沉积在神经和血管周围;⑷肌内膜和肌束膜结构变化:与安静对照组比较,训练组肌束膜胶原纤维结构紊乱,且厚度增加的肌内膜尤其是肌束膜collagenⅠ过度沉积。结论:⑴长期重复性离心运动导致骨骼肌过度使用损伤,包括骨骼肌细胞超微结构损伤累积,神经、血管和肌束膜纤维化;⑵骨骼肌细胞超微结构损伤累积导致肌内膜尤其是肌束膜collagenⅠ过度沉积,以保护肌膜免受进一步损伤;⑶collagenⅠ在肌内膜尤其是肌束膜持续沉积增加了结缔组织硬度,造成骨骼肌神经和血管结构损伤累积。表明骨骼肌细胞超微结构损伤累积导致了过度使用损伤症状发生。

The Mechanism of Eccentric Exercise-induced Skeletal Muscle Overuse Injuries

Objective The purpose of this study was to investigate the mechanisms of skeletal muscle overuse injury induced by chronic eccentric training.Methods Twelve male Sprague-Dawley rats were assigned randomly to control(C) and training(T) groups.Animal model of overuse injury was developed through 4-week low-intensity eccentric exercise(treadmill running,60~90 min/day,-16°slope,5 days/week).Vastus intermedius muscle was collected 4 weeks after the running.The ultrastructural damage of skeletal muscle was investigated by transmission electron microscope,and collagen structural change of skeletal muscle by scanning electron microscopy.The collagen deposition in skeletal muscle was evaluated by Masson's trichrome,expression of collagenⅠin collagen fiber was identified by immunohistochemistry and basement membrane of skeletal muscle cells by collagenⅣ staining.Results(1) Ultrastructural abnormalities in skeletal muscle including Z-band streaming,widened intermyofibrillar spaces,myofibril degradation,congestion of subsarcolemmal mitochondria,and accumulation of mitochondrial degradation products in intermyofibrillar were found in group T when compared to group C.(2) There was intact sarcolemma without sarcolemma disruption in group T.(3) Structure of nerves and blood vessels was damaged,and excessive collagen deposition around nerves and blood vessels were found in group T when compared to group C.(4) There were collagen fibers derangement in perimysium,and excessive collagenⅠprotein deposition in expanded endomysium,particularly in perimysium in group T when compared to group C.Conclusions(1) Chronic eccentric exercise resulted in overuse injuries in skeletal muscle.(2) Ultrastructural damage of skeletal muscle caused the excessive accumulation of perimysium collagenⅠfor protection of sarcolemma from further damage.(3) Continued excessive collagenⅠdeposition in endomysium,particularly in perimysium increased stiffness of connective tissue,induced damage of nerves and blood vessels,which resulted in clinical symptoms of overuse injury.