Efeito da terapia LED de baixa potência sobre o reparo do músculo esquelético após criolesão

Abstract

Phototherapy has shown positive effects on the modulation of the muscle regeneration process. Most studies that have shown effects used low-power lasers (LBPs) as light sources. However, more recent studies have also begun to investigate the possible effects of therapy using LED (TLED) during tissue repair. The objective of this study was to evaluate the effects of TLED on the morphology of muscle tissue, as well as on collagen remodeling and matrix metalloproteinase 2 (MMP-2) activity, in the skeletal muscle of rats after acute injury. Wistar rats were divided into 4 groups: (1) control; (2) sham; (3) cryoinjury; and (4) cryoinjury and TLED. The cryoinjury was induced by two metal probe applications cooled in liquid nitrogen directly onto the belly of the tibialis anterior (TA). For the treatment, the LED equipment (wavelength: 850 nm, output power: 30 mW, beam area of 1 cm² and total energy of 3.2J) was used daily. The study periods were 1, 3 and 7 days. The morphological aspects were evaluated by H&E staining, the amount and distribution of collagen fibers using picrosirius staining under polarized light and the gelatinase activity of MMP-2 using the zymography technique. The results showed significant reductions in inflammatory infiltrate after 3 days (P < 0.001) and an increased number of immature muscle fibers after 7 days (P < 0.01). Furthermore, the treatment induced a reduction in gelatinolytic activity of MMP-2 after 1 (p > 0.05), 3 (p < 0.01) and 7 (p < 0.01) days, when compared to the non-treated injured groups, and increased the deposition of collagen after 3 and 7 days in the treated groups (p < 0.01). Conclusion: LED 850 nm therapy produced a significant reduction in inflammation, decreased MMP2 activity and increased numbers of immature muscle and collagen fiber during the muscle repair process following acute injury.