Effects of electroacupuncture combined with passive stretch exercise on disused muscle atrophy and expression of skeletal troponin in mice

OBJECTIVE To observe the efficacy of electroacupuncture (EA) plus passive stretch exercise in the treatment of disused atrophy of gastrocnemius and soleus muscles in mice. METHODS Fifty C57BL/6 mice were randomly and equally divided into 5 groups: blank control, model, passive stretch exercise (exercise), EA and EA+exercise groups. The muscular atrophy model was established by fixing the gastrocnemius and soleus muscles with plaster immobilization (by putting the right leg into a plastic vial and then twining the vial with medical plaster bandage from the ankle upwards to the thigh and groin to maintain the knee-joint flexion and ankle joint plantar flexion for 7 days). EA (2 Hz/100 Hz, 1 mA)was applied to bilateral "Zusanli"(ST36) for 10 min, once a day for 4 weeks. For mice with the passive exercise, the plastic vial was removed first, followed by pulling out the hindleg to seize the toes to stretch them until the right hindleg is fully extended, then, pushed the leg towards the body. The procedures were repeated once again and again for 10 min. The exercise was conducted once daily, for 4 weeks. The cross-sectional area of fast and slow muscle fibers of the soleus and gastrocnemius was measured under electronic microscope after ATPase histochemical stain and the expression of slow skeletal muscle troponin (TNNI1) and fast skeletal muscle troponin (TNNI2) in the soleus and gastrocnemius was detected by Western blot. RESULTS Compared with the blank control group, the cross-sectional areas of the fast and slow muscle fibers of the soleus and gastrocnemius muscles were significantly decreased in the model group (P<0.05, P<0.01). Following the interventions, the cross-sectional areas of the fast and slow muscle fibers of soleus muscle in the EA+exercise group, and those of the fast and slow muscle fibers of the gastrocnemius muscle in the EA and EA+exercise groups, and the expression levels of TNNI1 and TNNI2 proteins in the gastrocnemius muscle of the EA+exercise group were significantly increased in comparison with the model group (P<0.05, P<0.01). CONCLUSION EA combined with passive stretch exercise can promote the recovery of the soleus and gastrocnemius muscles in disused muscle atrophy mice, which may be related to its effect in up-regulating the expression of TNNI1 and TNNI2 proteins.