The mechanism through which low-intensity pulsed ultrasound promotes the differentiation of C2C12 myoblasts / 中华物理医学与康复杂志

ABSTRACT

Objective:To observe the effect of low-intensity pulsed ultrasound (LIPUS) at different intensities on the expression of adiponectin and its receptors in C2C12 myoblasts, and to explore the potential mechanism by which LIPUS promotes the differentiation of C2C12 myoblasts.Methods:C2C12 myoblasts cultured in vitro were randomly divided into a control group and U 0.1, U 0.3 and U 0.5 groups. The control group received sham LIPUS exposure, while the U 0.1, U 0.3 and U 0.5 groups were exposed to LIPUS at intensities of 0.1W/cm 2, 0.3W/cm 2 or 0.5W/cm 2 respectively, and 1MHz for 5 min daily for 5 days. Cell viability was measured using CCK-8 assays. Fluorescence quantitative reverse transcription-polymerase chain reactions were used to detect the mRNA expression of adiponectin, adiponectin receptor 1 (adipoR1) and T-cadherin in the cells. Western blotting was employed to assess the protein expression of adiponectin, adipoR1, T-cadherin, adenosine monophosphate activated protein kinase (AMPK), activated phosphorylated adenylate-activated protein kinase (P-AMPK), embryonic myosin heavy chain (eMHC) and myogenin (MYOG). The differentiation ability of the 4 groups was measured using cell immunofluorescence chemistry. Results:After the intervention the cell viability in the U 0.1, U 0.3 and U 0.5 groups was significantly higher than in the control group. Compared with the control group, the average mRNA expression of adiponectin and the receptors of adipoR1 and T-cadherin were up-regulated significantly in the U 0.3 and U 0.5 groups. The average adiponectin, adipoR1 and T-cadherin protein expressions, and the AMPK phosphorylation level in the U 0.3 and U 0.5 groups had increased significantly compared with the control group, but all were significantly lower than in the U 0.3 group. The average protein expression of eMHC and MYOG, and the C2C12 myoblast fusion indices of the U 0.3 and U 0.5 groups were significantly higher the control group′s averages. Conclusions:LIPUS can promote the differentiation of C2C12 myoblasts. It is most effective at 0.3W/cm 2, administered for 5min/d at 1MHz with a 20% duty cycle. Its regulatory mechanism may be related to up-regulation of the expression of adiponectin, the adipoR1 and T-cadherin receptors, and the activation of AMPK phosphorylation in C2C12 myoblasts.