Ultrasound modulates the inflammatory response and promotes muscle regeneration in injured muscles.

The purpose of this study was to examine the effect of ultrasound on inflammatory skeletal muscle in vitro and in vivo. C2C12 cells were cultured in medium with or without TNF-α or IL-1β. After stimulation with cytokines, the cells received ultrasound or sham exposure. Furthermore, the tibialis anterior (TA) muscle in C57BL/6 mice injured by cardiotoxin (CTX) were dissected after a series of ultrasound treatments and examined. Exposure of C2C12 cells to ultrasound resulted in down-regulation of cyclooxygenase-2 (COX-2) mRNA and protein expression induced by TNF-α or IL-1β, and up-regulated myogenin mRNA and protein depressed by TNF-α or IL-1β. In injured TA muscle induced by CTX, ultrasound caused increase of COX-2 mRNA at 1 day after ultrasound treatment, however, at day 5, reduction of COX-2 mRNA and protein. At day 5, ultrasound caused increase of myogenin mRNA and protein, increase of fast myosin protein, and increase of paired-box transcription factor 7 positive cells. At day 7, the cross-sectional area of myofibers in the ultrasound exposure side was significantly larger than that on the control side. In conclusion, ultrasound stimulation may be a better candidate as a medical remedy to promote myogenesis in inflammatory muscle states, such as muscle injury.