Efeito do laser infravermelho aplicado em diferentes momentos sobre a expressão gênica das cadeias pesadas de miosina, calcineurina e miostatina durante o processo de reparo do músculo esquelético de ratos

Abstract

The high incidence of cases of muscle injury motivates the search for new therapeutic alternatives for a muscle regeneration process faster and better quality. With the evolution of technology and availability of increasingly perfected capabilities, studies show major advancement in muscle regeneration, especially the fotobiomodulation (PBM) using low-level laser terapy (LLLT). Studies on the prior application or post-injury have shown positive effects, yet there is still little information in relation to their effects on the protein expression related to functionality and trophism muscle fiber after an injury. Myostatin is a protein involved in muscle growth/development, calcineurin is involved in muscle contraction, and the MHCs determine muscle performance about the strength and speed. The present study aimed to evaluate the effect of LLLT applied prior to the induction of muscle injury, associated or not to post irradiation on the gene expression of myosin heavy chains, calcineurin and myostatin. 65 Wistar rats were used, divided into 4 experimental groups: control (n = 5); Untreated Cryoinjury (n = 20); Cryoinjury treated previously with LLLT (n = 20) and Cryoinjury treated with LLLT pre-and post-injury (n = 20). The Cryoinjury constituted of two applications of bat cooled in liquid nitrogen in the muscle tibialis anterior (TA). The injured were euthanized in groups 1, 3, 7 and 14 days after the induction of injury. Irradiation with LLLT was done with the laser AsGaAl (780 nm) in the parameters of 10 J/cm ²; 40 mW; 10 seconds per point; 8 points; 3.2 J total energy. At the end of the protocol, the TA muscles were removed for analysis of gene expression of myosin heavy chains (MHCs), calcineurin and myostatin by real-time PCR. The comparison between the groups was performed by ANOVA/Tukey (p < 0.05) through the BioStat 5.0 program. The results showed that the previous irradiance reduced the expression of myostatin after 3 days. Prior irradiation associated with post irradiation reduced the expression of calcineurin in 14 days and increased the expression of myostatin in the same period. As for the expression to MHCs, the LLLT radioed the muscle repair process especially in the acute phase, the previous irradiance decreased the expression of MHC I and MHC IIx in 1 day, and the prior irradiation associated with post irradiation increased the expression of MHC IIx in 3 days. In conclusion, the LLLT was able to modulate important proteins for muscle repair process (MHCs, calcineurin and myostatin), being more obvious its effect when adopted the regime of prior application associated to post-injury irradiation.