Efeito da fotobiomodulação vascular (FBMV) transcutânea sobre o processo inflamatório e o reparo muscular em modelo de lesão aguda

Abstract

The photobiomodulation therapy (PBM) has shown positive effects concerning the modulation of the inflammatory process and on the muscle repair process when applied locally. However, there are few studies on the mechanisms of action of vascular photobiomodulation (VPBM), a non-invasive method of vascular irradiation, on muscle repair. Thus, the aim of this study was to evaluate the effect of VPBM using low-level laser (LLL) on the inflammatory process and skeletal muscle repair of rats when applied before or after cryoinjury-induced acute muscle injury in the tibialis anterior (TA) muscles. Concomitantly, as a secondary objective, a systematic literature review was performed involving the use of non-invasive VPBM and ILIB (systemic photobiomodulation) using LLL in experimental models (Appendix A). To conduct this study, Wistar rats were used and evaluated in the following experimental groups: (1) Control; (2) Non-injured + VPBM; (3) Injured; (4) Prior VPBM + Injury; (5) Injury + post-PVBF. VPBM was performed in transcutaneous contact over the vein/artery at the base of the tail of the animals (780 nm; 40 mW; 0.04 cm2; 80 J/cm2). Euthanasia of the animals was performed at 1, 2, 5, and 7 days after induction of the injuries. TA muscles were collected for qualitative and quantitative histological analysis by H&E and protein expression of TNF-α and MCP-1 by ELISA. Blood samples were collected and submitted to a quantitative automatic hematological analyzer and a leukocyte differential counter. Data were subjected to statistical analysis (ANOVA/Tukey). The results showed that VPBM applied prior to injury induced an increase in circulating neutrophils (granulocytes) after 1 day and an increase in monocytes after 2 and 5 days in relation to the Non-Injured + VPBM and Injured groups. An increased in erythrocytes, as well as in hemoglobin concentration were observed in the Non-Injured + VPBM group on days 1 and 2 in comparison to the Injured group. There were no differences in the evaluation of hematological components and coefficients, such as hematocrit, platelet concentration, platelet count, and the amplitude of platelet distribution when comparing all experimental groups. Regarding histological aspects, only the Prior VPBM + Injured group showed a reduction in the number of inflammatory cells after 1, 5 and 7 days and an increase in blood vessels at 5 days. Both groups, Prior VPBM + Injured and Injured + VPBM after, showed a decrease of myonecrosis at 1, 2 and 7 days, an increase of newly and immature fibers after 5 and 7 days, and neovascularization after 1, 2 and 7 days. Regarding protein expression, there was an increase in MCP-1 after 1 and 5 days and TNF-α after 1, 2, and 5 days in the Injured + VPBM after group in comparison to the other experimental groups. The Prior VPBM + Injured group showed increased MCP-1 production after 2 days in comparison to the Non-Injured + VPBM and Control group. On day 7, the Injured group still shows an increase in MCP-1 protein expression when compared to the VPBM groups. In conclusion, VPBM was able to modulate hematological aspects, circulating leukocytes, the protein expression of the chemokine MCP-1 and the pro-inflammatory cytokine TNF-α and the inflammatory process, showing a reduction of myonecrosis and restoration of tissue architecture with increase of newly and immature muscle fibers and neovascularization, presenting more pronounced effects when the VPBM was applied prior to the muscle injury.