Comparative effect of low-level laser therapy and low intensity ultrasound on myofiber phenotypes, oxidative stress and proteins during muscle repair

Abstract

Muscle injuries represent a major clinical conditions found in the rehabilitation center. Among the major therapeutic resources used in physical therapy clinics for the treatment of muscle injuries are the Low-Level Laser Therapy (LLLT) and Low-Intensity Pulsed Ultrasound (LIPUS). Both therapeutic resources have presented good results with respect to modulation of the muscle repair process, but there is not description on how it could influence the determination of the phenotype of the newly formed fibers in the type of myosin heavy chain (MyHC) expresses literature and little is known about its effects on oxidative stress. Furthermore, there is a need to determine the molecular mechanisms involved, as well as the methodology and suitable dosimetric parameters. The objective of this proposal is to evaluate the effects of LLLT and LIPUS on the expression of isoforms of MyHC, the expression and synthesis of proteins involved in muscle repair (myostatin and calcineurin) and oxidative stress during the repair process of skeletal muscle of rats. Wistar rats will be divided into four groups: 1) control; 2) cryoinjured without treatment; 3) cryoinjured treated with LLLT and 4) cryoinjured treated with LIPUS. Analyses will be performed at 3, 6, 12 and 24 hours for analysis of oxidative stress, and 3, 7 and 14 days for analysis of MyHC, myostatin and calcineurin. Cryoinjury will be performed on the belly of the tibialis anterior (TA) muscle. LLLT will be performed daily using the MMOptics GaAlAs laser (wavelength of 780 nm) using an energy density of 10 J/cm², an output power of 40 mW, a beam spot of 0.4 cm² and time of 10 seconds. The treatment with LIPUS will be performed using the Sonomaster® equipment with the frequency of 1 MHz, an intensity of 0.4 W/cm², a pulsed model cycles 1:4 and stationary application of 3 minutes. For the analysis of gene expression will be extracted total RNA of the TA muscle and will obtain cDNA for performing Real-time PCR using specific primers for each gene and proteins analysis will be performed using enzyme-linked immunosorbent assays (ELISA) and Western blotting, the stress oxidative will be performed by lipid peroxidation (LPO) and the damage to proteins, and the analysis of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx). (AU)