ELF-MF transiently increases skeletal myoblast migration: possible role of calpain system

Purpose: Cell migration is crucial for myogenesis since it is required for the alignment and fusion of myoblast. Ca2+ signals are involved in regulating myoblast migration and an extremely low frequency (ELF) magnetic field (MF) increases intracellular calcium levels in C2C12 myoblast. This study was aimed to investigate whether ELF-MF could affect myoblast migration. As calpains contribute to the regulation of myoblast motility the effect of ELF-MF on µ- and m-calpain was also investigated. Materials and Methods: The effect of ELF-MF (1 mT; 50 Hz) on C2C12 cell motility was observed by wound-healing assay. Protein expression of calpains, calpastatin, myristoylated alanine-rich C-kinase substrate (MARCKS) and vinculin were examined by Western-blot analysis. Casein zymography and immunofluorescence analysis were carried out to evaluate, respectively, activity levels of calpains and intracellular distribution of calpains, calpastatin and actin. Results: Exposure to ELF-MF resulted in a transient but significant increase of myoblast migration. This stimulatory effect was associated with a marked increase of µ- and m-calpain activity followed by the concomitant variation in their subcellular localization. No significant changes in intracellular distribution and protein levels of calpastatin were detected. Finally, a significant decrease of MARCKS expression and modifications of actin dynamics were reported. Conclusions: This study clearly outlines an involvement of calpains in ELF-MF-mediated myoblast migration.