FOTOBIOMODULAÇÃO E FIBRINA RICA EM PLAQUETAS NO MÚSCULO GASTROCNÊMIO SUBMETIDO A TENDINOPATIA CALCÂNEA EM RATOS

Abstract

The pathological process of calcaneal tendinopathy is primarily initiated by repetitive overload of the tendon, leading to structural damage to collagen fibrils. The disease typically presents as a triad of pain, edema, and impaired function. When it becomes chronic, it can affect the gastrocnemius muscle, causing an inflammatory process and muscle hypotrophy. Multiple rehabilitation strategies have been recommended for patients with tendinopathy, such as photobiomodulation and advanced platelet-rich fibrin injection. Objective: To compare the treatment effects of photobiomodulation and the application of advanced platelet-rich fibrin in the gastrocnemius muscle subjected to calcaneal tendinopathy. Methodology: This is an experimental study. Seventy-five rats were divided into five groups: control group (CG), injury group (IG), advanced platelet-rich fibrin group (APRF-G), photobiomodulation group (PBM-G), and advanced platelet-rich fibrin + photobiomodulation group (APRF+PBM-G). The animals were induced to calcaneal tendinopathy by transverse clamp compression of the calcaneal tendon. The photobiomodulation treatment was applied on the 2nd, 4th, and 6th days after induction, while the APRF-G animals received treatment only on the 2nd day after induction. The combined therapy group received treatments at the same frequency as the isolated therapies. On days D0, D7, D14, and D21, the animals were evaluated through a manual grip strength test. On D7, D14, and D21, the animals were euthanized for muscle collection and subsequent histological and morphometric analysis of fibers and neuromuscular junctions. Results: The IG group showed lower muscle strength compared to the other groups. The PBM-G, APRF-G, and APRF+PBM-G groups exhibited increased muscle strength between the seventh and twenty-first days of the experiment. When analyzing the morphology and histomorphometry of the gastrocnemius muscle, no signs of muscle injury were found, indicating muscle recovery with the applied treatments. Regarding connective tissue analysis, the APRF+PBM-G group showed an increase in type III collagen. Neuromuscular junction (NMJ) analysis revealed differences in area, major diameter, and minor diameter, with groups treated with advanced platelet-rich fibrin injection presenting smaller NMJs compared to the CG, IG, and PBM-G groups. Conclusion: The findings of this study suggest that combined therapies had a greater reparative effect on muscle tissue, primarily through the increase of type III collagen, compared to isolated treatments.