Effects of Electroacupuncture on Adaptive Hypertrophy of Gastrocnemius and Proliferation and Differentiation of Muscle Satellite Cells in Rats

Abstract

To explore the effects and mechanism of different duration electroacupuncture (EA) on adaptive hypertrophy of gastrocnemius and the expressions of proliferation cell nuclear antigen (PCNA), paired box transcription factor 7 (Pax 7), myogenic differentiation antigen (MyoD 1), myogenin (MyoG), myosin heavy chain-Ⅰ(Myh 7), transforming growth factor-β 1 (TGF-β 1), Smad 3 in rats. Twenty-four SD adult male rats were randomly divided into normal, two-week EA (A 2), four-week EA (A 4) and eight-week EA (A 8) groups, 6 rats in each group. Except the normal group, EA was applied at right "Zusanli" (ST 36) and "Huantiao" (GB 30) for 10 min in the other three groups, separately for 2 weeks, 4 weeks and 8 weeks, once a day, 6 times a week. The ratio of gastrocnemius wet weight was calculated after EA. The cross-sectional area and diameter of muscle fiber were measured after HE staining. The expression of PCNA protein was detected by immunofluorescence. The relative expressions of Pax 7, MyoD 1, MyoG, Myh 7, TGF-β 1 and Smad 3 mRNA were tested with real-time PCR. The expressions of PCNA protein were obviously higher in the A 2 and A 4 groups than that in the normal group. The expression of genes in the EA intervention groups showed a trend of increasing first and then decreasing except Smad 3 mRNA. The relative expressions of Pax 7 and TGF-β 1 mRNAs reached their peaks in the A 2 group compared with those in the normal group (P<0.01). The ratio of gastrocnemius wet weight, cross-sectional area and diameter of muscle fiber, and the relative expressions of MyoD 1, MyoG, Myh 7 mRNAs reached their peaks in the A 4 group (P<0.01), while the relative expression of Smad 3 mRNA showed a trend of decreasing first and then increasing and reached its bottom at the 4th week (P<0.01). EA at "Zusanli" (ST 36) and "Huantiao" (GB 30) may induce adaptive hypertrophy of gastrocnemius in rats by up-regulating the expressions of Pax 7, PCNA, TGF-β 1, MyoD 1, MyoG, Myh 7 and down-regulating the expression of Smad 3, promoting the proliferation of skeletal satellite cells, myogenic differentiation, myotubes terminal differentiation, increasing the wet weight, fiber cross-sectional area and diameter of gastrocnemius.