[Effect of electroacupuncture of acupoints on the healthy limb (opposing needling) on acute skeletal muscle contusion in rats].

Objective: To observe the therapeutic effect of electroacupuncture (EA) of "Zusanli" (ST36) and " Ashi "-point on the healthy side (opposing needling) on muscular injury and expression of myogenin (myoG) and fast myosin skeletal heavy chain (Fast MyHC) proteins in the gastrocnemius muscle (GM) tissues in skeletal muscle contusion rats，so as to explore its mechanism underlying improvement of skeletal muscle injury.
Methods: A total of 54 male SD rats were divided into normal control (n ＝ 6)，model ( n ＝24) and opposing needling (EA, n ＝24) groups. The latter two groups were further randomized into 3, 5, 7 and 14 d subgroups ( n ＝6 per subgroup). The skeletal muscle contusion model of the hind-limb was established by using a self-made striking device. EA (1 Hz/3 Hz，1－2 mA) was applied to ST36 and " Ashi "-point on the uninjured side of the hind-limb for 15 min every time, once a day for 3, 5, 7 and 14 days, respectively. The injured GM was harvested on the 3 ^rd, 5 ^th, 7 ^th and 14 ^th day after muscular contusion. The morphological changes of the injured GM and the mean cross-sectional areas (CSAs) of the neonatal muscle cells were observed by microscope after H．E. staining. The immunoactivity of desmin protein (myogenic marker protein of myoblast cell) of GM was detected by immunofluorescence stain on the 7 ^th day after injury, and the expression levels of myoG (on the 3 ^rd and 5 ^th day after injury) and fast MyHC protein of GM tissues (on the 7 ^th and 14 ^th day after injury) were detected by Western blot.
Results: H．E. staining of GS tissue showed fewer neuronal myocytes with disordered arrangement at different sizes, and appearance of some collagenous fibers among the mesenchyme on day 7 and 14 after muscular contusion, which was relatively milder in the EA group. In the EA group, the CSA values of the neonatal muscle cells were significantly larger than those in the model group on the day 7 ^th ( P <0.05), 14 ^th ( P <0.001) after injury. On day 7 after muscular contusion, the desmin was found to express on the cellular membrane of GM in the normal control group, while in the model group, the desmin expressed mainly in the cellular plasma in the model group, and on the cellular membrane of neonatal myocytes in the EA group, respectively. The desmin positive myocytes showed disordered arrangement and different sizes after muscular contusion, whereas the situations of the EA group were close to those of the normal control group. Desmin expression was up-regulated in the EA group compared with the model group which was not significant difference ( P >0.05). On the 3 ^rd and 5 ^th day after muscular contusion, the expression level of myoG protein was significantly up-regulated in the model group compared with the normal control group ( P <0.001), and significantly up-regulated in the EA group than that in the model group ( P <0.001). On the 7 ^th and14 ^th day after contusion, the expression level of fast MyHC protein was significantly down-regulated in the model group relevant to the normal control group ( P <0.001), and markedly up-regulated in the EA group relevant to the model group ( P <0.01)．.
Conclusion: EA of ST36 and " Ashi "-point on the contralateral limb can up-regulate the expression of myoG and fast MyHC proteins of GM in acute skeletal muscle contusion rats, which may contribute to its effect in promoting the repair of skeletal muscle injury.