Low level laser therapy accelerates the extracellular matrix reorganization of inflamed tendon

Abstract In tendon lesions, inflammation indicates the beginning of tissue repair and influences cell proliferation and the remodeling of the extracellular matrix (ECM). Low level laser (LLL) therapy has been an important method to induce tissue repair, and several studies have sought to better understand the therapeutic possibilities of this modality. This study analyzed the effect of LLL on the ECM of rat tendons during the early phase of the inflammatory process. Wistar rats received an intratendinous application of carrageenan adjacent to the osteotendinous region in the right paw. The animals were divided into the following groups: G1—intact, G2—animals with no treatment after the inflammation induction, G3—animals treated with LLL 1 and 3 h after induction of inflammation (4 J/cm 2 continuous). After 4 h of application, the animals of the two groups were euthanized with isoflurane overdose. Our results demonstrate that LLL therapy can promote decrease in non-collagenous protein and glycosaminoglycans content, as well as an increase in metalloproteinases −9, which proved, for the first time, that LLL therapy promotes alterations in the inflamed tendons even when analyzed only four hours after this process occur and could be a useful tool to improve the balance in inflamed tissues.