Effect of electroacupuncture on amyotrophia and expression of myogenic differentiation-related genes of gastrocnemius in rats with chronic constriction injury of sciatic nerve

Abstract

To explore the effect of electroacupuncture(EA) on amyotrophia and expression of paired box7(Pax7), myogenic differentiation antigen-1 (Myod1), myogenin (Myog), myosin heavy chain- Ⅱa (Myh2), myosin heavy chain-Ⅱx (Myh1) and myosin heavy chain-Ⅰ (Myh7) of denervated gastrocnemius in rats with chronic constriction injury (CCI) of the right sciatic nerve, so as to explore its mechanisms underlying postponing development of amyotrophia. Sixty-six SD adult male rats were randomly divided into sham operation (sham) group (n＝24), model group (n＝24) and EA group (n＝18). The denervated muscle (gastrocnemius) atrophy model was established by CCI of the right sciatic nerve. EA (2 Hz，1.0 mA) was applied to the right "Zusanli"(ST36) and "Huantiao"(GB30) for 10 min, once a day, six times a week and for 1, 2 and 4 weeks, respectively. After complete dissection of bilateral gastrocnemius muscles, their wet weight levels were measured and the ratio of wet weight (＝that of the operation side/that of the non-operation side) was calculated, and the cross-sectional area (CSA) and diameter of the gastronemius were detected after fixation in 4% paraformaldehyde, sectioning, and H．E. staining. The expression levels of Pax7, Myod1, Myog, Myh2, Myh1 and Myh7 mRNAs in the gastrocnemius tissue after 3 weeks of modeling were detected with quantitative real time-PCR (qPCR). After 1 week of modeling, the ratios of wet weight of gastrocnemius and the CSA and fiber diameter at the 2nd, 3rd and 5th week were significantly smaller in the model group than in the sham group (P<0.05). The expression levels of Myod1 and Myog mRNAs were significantly up-regulated (P<0.01), and those of Myh2, Myh1 and Myh7 considerably down-regulated in the model group compared with the sham group (P<0.05, P<0.01). No significant changes were found in the expression levels of Pax7 mRNA after modeling and EA intervention (P>0.05)．Following EA intervention, the CSA and diameterof the gastronemius were obviously increased (P<0.05), and the expression levels of Myod1, Myog and Myh7 further markedly or remarkably up-regulated in comparison with the model group (P<0.05, P<0.01). No significant changes were found in the ratio of wet weight of gastrocnemius at the 3 time-points, and the expression levels of Myh2 mRNA and Myh1 mRNA in the EA group relevant to the model group after 3 weeks of modeling (P>0.05). EA treatment may delay gastrocnemius atrophy in CCI rats, which is possibly associated with its effects in up-regulating the expression of Myod1, Myog and Myh7 mRNAs to control the differentiation of the satellite cells and the muscle fiber type transformation.