Photobiomodulation and platelet-rich fibrin in the gastrocnemius muscle submitted to calcaneal tendinopathy in rats.

The study investigated the impact of different treatments on recovery from calcaneal tendinopathy in rats, focusing on the gastrocnemius muscle. Tendinopathy is caused by repetitive overload, leading to structural collagen damage and chronic muscle inflammation. Three therapeutic approaches were compared: photobiomodulation (PBM), advanced platelet-rich fibrin (A-PRF) injection, and a combination of the two. Seventy-five rats were separated into five groups: control (CON), injury (LES), PRF (A-PRF), photobiomodulation (PBM) and combined therapy (A-PRF + PBM). Tendinopathy was induced by compression of the calcaneal tendon. The treatment was applied at specific intervals, and the animals were assessed for muscle strength and subjected to histological and morphometric analysis of the muscle. LES showed the lowest muscle strength. The treated groups (PBM, A-PRF and A-PRF + PBM) had an increase in strength between days 7 and 21, but there were no signs of muscle damage or significant recovery in the muscle fibers. The combined therapy group showed greater production of type III collagen in the connective tissue, indicating a more significant repair effect. In contrast, the neuromuscular junctions in the groups treated with PRF were smaller, suggesting possible structural alterations. The combination of therapies showed superior results to treatment alone, promoting greater tissue repair in the gastrocnemius muscle, especially due to the increase in type III collagen.