The interactions between muscle and the macrophages that invade this tissue after the occurrence of injury are crucial to the repair process. Low-level laser therapy (LLLT) has been widely used in clinical and experimental settings for the treatment of muscle injuries. However, little is known regarding the effects of laser irradiation on macrophages. The main objective of this project is to compare the effect of LLLT (red and infrared) on the gene expression and protein synthesis of 3 products (that may play an important role in the muscle repair process) of activated macrophages. The secondary objective is to evaluate the differentiation and fusion of myogenic precursor cells (C2C12) cultivated with macrophages supernatants. For this purpose, J774 macrophage cultures will be activated (inflammatory phenotype, M1) for 24h, washed and will receive 4 different laser irradiation parameters (660 and 780nm; 40 mW; 10J/cm2; 0,4J or 660 and 780 nm; 20mW; 5J/cm2; 0,2J). After the incubation period (24h), the gene expression of cytokines IL-6, TNF-± and IL-1² will be evaluated using quantitative PCR. The supernatant of the cultures from the different experimental groups (24h after irradiations) will be used to assess protein production from macrophages (ELISA) and also to treat myogenic precursor cells (C2C12) in order to analyze their differentiation and fusion. In each experimental situation, non-irradiated cells will serve as controls. Three independent experiments will be performed under each condition. For in vivo analysis, Wistar rats will be allocated into four groups: control (n=5); injury group (n=15); injury + red LLLT group (n=15); and injury + infrared LLLT group (n=15). After 2, 4, and 7 days, the animals will be sacrificed and the muscles will be removed and processed for immunohistochemistry. M1 (CD68 and CD80 labeling), macrophage profile will be identified and will be correlated with the different stages of the skeletal muscle repair process. The histological analysis will include total inflammatory cells, myonecrosis, blood vessels and immature muscle fibers. All results will be statistically analyzed.
News published in Agência FAPESP Newsletter about the scholarship: