Efeitos da fotobiomodulação na diferenciação, viabilidade e migração de mioblastos C2C12 expostos a diferentes concentrações de dexametasona durante a indução da diferenciação

Abstract

Skeletal muscle preserves its function through a balance of proliferation, differentiation, and regeneration, processes that depend on the activation of satellite cells. Following injury, these cells give rise to myoblasts, which differentiate and restore muscle fibers. Although dexamethasone is an effective anti-inflammatory agent, it compromises muscle repair by inducing atrophy and other adverse metabolic effects. Photobiomodulation has the potential to enhance myoblast viability, proliferation, and differentiation, as well as modulate inflammation and support muscle trophism, possibly through mitochondria-dependent mechanisms. However, few studies have examined its effects in glucocorticoid-induced atrophy. The aim of this study was to assess the effects of PBM on differentiation, viability, migration, and inflammatory cytokine production in C2C12 myoblasts exposed to different concentrations of dexamethasone (DEXA). Five experimental conditions were analyzed: C2C12 cells in proliferation medium; cells in differentiation medium exposed to PBM; a differentiation-medium control; cells treated with DEXA (5, 10, or 200 µM) during differentiation; and cells treated with the same DEXA concentrations in combination with PBM. PBM groups were irradiated with dosimetric parameters using a 780-nm laser, 70 mW output power, 15-second exposure, and a radiant exposure of 26.25 J/cm². Cell viability, proliferation, and migration were evaluated using the MTT assay, crystal violet staining, and wound-healing assay, respectively. Myoblast differentiation was assessed by nuclear counting and fusion index using May–Grünwald–Giemsa staining. IL-6 and TNF-α levels were quantified by ELISA. Three independent experiments were performed, and analyses were conducted at 24, 48, and 72 hours. All data were subjected to statistical analysis. The results showed that DEXA reduced C2C12 viability in a time- and concentration-dependent manner, with greater cytotoxicity at 10 and 200 µM. PBM partially attenuated these effects, preserving viability and promoting proliferation, particularly between 24 and 48 hours. During differentiation, DEXA impaired myotube formation and decreased the fusion index, whereas PBM alone enhanced myogenesis and, when combined with DEXA, mitigated part of the damage, maintaining more elongated and organized cells. The migration assay revealed that DEXA impaired wound closure over time, and PBM did not reverse this effect under the tested conditions. IL-6 and TNF-α levels were also suppressed by DEXA in a time- and dose-dependent manner, and PBM partially modulated this reduction. Taken together, these findings indicate that PBM exerts protective effects on myoblasts exposed to dexamethasone by supporting bioenergetic, proliferative, and early differentiation processes, although its efficacy is limited at higher drug concentrations. These results suggest that PBM may be a promising strategy to mitigate glucocorticoid-induced damage, although further studies are needed to clarify its impact on migration and inflammatory modulation.