| Backgroud:Musculoskeletal injuries are the highest incidence of damages in unintentional injury, of which skeletal muscle injuries accounts for about 60-67%, and have serious impact on people’s daily lives, particularly on athletes that affect the daily workout and professional performance. After skeletal muscle injury invalid repair such as scarring, atrophy of skeletal muscle and skeletal muscle denervation, etc., will seriously affect the normal recovery of limb function. How to promote skeletal muscle regeneration effectively after injury, has become a hot research issues at home and abroad. Literature studies show that electroacupuncture (EA) therapy can promote the repair and regeneration of skeletal muscle after injury, and promote wound healing; The wide range clinical applications of EA are proven effective to promote nerve regeneration by promoting reinnervation and establish contact between the neuromuscular junction (NMJ). Our preliminary studies indicated that EA the ST36 and Ashi acupoints can promote rabbit gastrocnemius (GM) regeneration by improving microcirculation perfusion, promoting the recovery of myofiber structure, and inhibiting excessive fibrosis, but the effects of EA on the recovery of GM electrophysio logical and biomechanical properties after contusion are not yet clear. Only skeletal muscle restores its inherent electrophysiological and biomechanical properties, which is the true definition of recovery.Objective:The purpose of this study was to investigate the effects and related mechanism of EA on Zusanli (ST36) and Ashi acupoints in promoting the recovery of the electrophysiological and biomechanical properties of rabbit GM after contusion. And thus lay the foundation for EA in promoting the functional recovery of skeletal muscle after injury, providing a theoretical basis for clinical application.Mathods:Ninety rabbits were randomly divided into three groups:the normal group (n =30), the contusion group with no treatment (n=30, contusion group), and the EA-treated experimental group (n=30, EA group). After an acute GM contusion was produced (in rabbits in the contusion and EA groups), rabbits in the EA group were treated with electrostimulation at the ST36 and Ashi acupoints with 0.4 mA (2 Hz) for 15 min. The contusion group received no EA treatment. At different time points (7,14, and 28 days) after contusion, we performed surface electromyography (EMG) and measured the nerve conduction velocity (NCV) of the GM and the GM branch of the tibial nerve. We also examined acetylcholinesterase (AchE) and Agrin expression in the neuromuscular junction (NMJ) via immunohistochemistry. Tensile test was applied to measure the ultimate load, ultimate strength, yield load, yield strength, and Young’s modulus of GM.Results:Compared with the contusion group, the EMG amplitude and NCV in rabbits in the EA group were significantly higher at all time points after contusion. AchE and Agrin expression in the EA group were significantly higher than those in the contusion group. On day 28 after contusion, all biomechanical measurements except Young’s modulus in the EA group were obviously higher at three time points compared with the contusion group. Young’s modulus reflecting the stiffness of GM was significantly greater in the EA group than in the contusion group.Conclusions:Our results showed that EA at the ST36 and Ashi acupoints effectively promoted recovery of the electrophysiological properties of the rabbit GM after contusion. The effects of EA were realized by promotion of the regeneration of myofibers and nerve fibers, as well as acceleration of NMJ reconstruction by upregulation of AchE and Agrin expression in the motor endplate area.Our results also showed that electroacupuncturing the ST36 and Ashi acupoints could effectively promote the recovery of rabbit GM biomechanical properties after contusion. The therapeutic effect was the best on day 28 after contusion. The mechanism may be closely related to the effects of EA on promoting muscle fiber regeneration, micro-structure restoration, and capillary network reconstruction. However, these conclusions need to be verified by further studies. |
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