Efeitos da fotobiomodulação vascular no trofismo muscular e na expressão de MuRF-1 e miostatina durante a regeneração muscular após lesão aguda

Abstract

Skeletal striated muscle plays essential roles, such as maintaining posture and facilitating human body movement. Due to its size and high demand, it is particularly susceptible to injuries, although it possesses a remarkable capacity for regeneration. This process is complex and involves the expression of myogenic transcription factors at different stages. Photobiomodulation (PBM) has shown positive results in muscle regeneration, gaining attention as a non-invasive treatment with no reported side effects. Most studies focus on locally applied PBM (LPBM), proving effective when applied either before or after injury. More recently, vascular photobiomodulation (VPBM) has also shown promising effects in this context, leading to increased research interest. This study aims to evaluate the effects of VPBM, alone or combined with LPBM, on tissue morphology, muscle fiber phenotype determination, and the expression of myogenic factors and proteins involved in muscle trophism during the regeneration process after the induction of acute muscle injury in an animal model. A total of 105 Wistar rats were used, divided into six experimental groups: (1) control, (2) injury, (3) VPBM pre-injury, and (4) post-injury + VPBM. VPBM was applied transcutaneously and pointwise over the animals' caudal artery/vein. using the following parameters for both treatments (780 nm; 40 mW; 0.04 cm²; 80 J/cm²; 3.2 J). The anterior tibial (AT) muscles of the animals were cryolesioned bilaterally by applying a nitrogen-cooled rod (10 seconds/2X), and euthanasia was performed at 1, 2, 5, and 7 days post-injury. AT muscles were collected for diameter and cross-sectional area analysis of muscle fibers through H&E-stained slides. Gene expression analysis of factors such as Myostatin, and MuRF-1 was performed by qPCR. The data were submitted to statistical analysis (ANOVA/Tukey). The results showed that after 1 day, the pre-injury FBMV treatment showed a decrease while the Lesion and post-injury FBMV groups exhibited an increase in comparison to the control group. At 2 and 5 days, the treated groups showed a reduction in diameter compared to the Lesion group. By day 7, the treated groups reached values similar to the control, while the Lesion group showed a reduction. Regarding AST, on day 1, the pre-injury FBMV treatment showed a decrease , while the Lesion and post-injury FBMV groups exhibited an increase. On day 2, no significant differences were observed between the groups. After 5 days, the Lesion and post-injury FBMV groups showed a significant increase, whereas the preventive treatment maintained values close to the control. By day 7, the FBMV-treated groups displayed AST values higher than the Lesion group but close to the control. With respect to the expression of MuRF-1 and myostatin, the injury group exhibited a significant upregulation of both proteins at 1, 2, and 5 days compared to the control, pre-injury FBMV, and post-injury FBMV groups. At seven days, myostatin levels remained elevated in the pre-treatment group compared to the control, injury, and post-injury FBMV groups, whereas MuRF-1 expression remained consistently elevated in the injury group. In conclusion, vascular photobiomodulation (FBMV) demonstrated beneficial effects on muscle regeneration by modulating morphological parameters and the expression of key proteins such as myostatin and MuRF-1. The pre-injury treatment exhibited a more pronounced impact at seven days, whereas post-injury application facilitated progressive recovery, mitigating muscle damage and reducing AST levels. Both treatment protocols effectively approximated the outcomes to control levels by the seventh day, underscoring the potential of FBMV as a non-invasive therapeutic strategy for muscle injuries.