Low-level laser therapy enhances muscle regeneration through modulation of inflammatory markers

Abstract Objective: The purpose of this study was to evaluate the in vivo response of two different laser fluences (4 and 8 J/cm2) on molecular markers involved in muscle repair after a cryolesion of the tibialis anterior (TA) muscle. Study design: Forty-eight male Wistar rats were randomly distributed into six groups: control (C); normal/uninjured TA muscle treated with either 4 J/cm2 (L4J) or 8 J/cm2 (L8J) laser irradiation; injured TA muscle without treatment (IC); and injured TA muscle treated with either 4 J/cm2 (IL4J) or 8 J/cm2 (IL8J) laser irradiation. The injured region was irradiated daily for 5 consecutive days, starting immediately after the cryolesion was set using a GaAlAs laser (continuous wave; wavelength, 830 nm; tip area, 0.0028 cm2; power, 20 mW). The animals were euthanized on the sixth day after injury. The injured right TA muscles were removed for histological evaluation, zymography, and immunoblotting and biotin switch analyses. Nitrite and nitrate plasma levels were measured to evaluate the nitric oxide (NO) production. Results: After low-level laser therapy (LLLT), in both injured treatment groups (IL4J and IL8J) the injured area was reduced, the NO production decreased and the S-nitrosated COX-2 was lowered. Moreover, both laser fluences increased the activity and expression of MMP-2. Conclusion: These results suggest that LLLT, for both fluences, could be an efficient therapeutic approach to modulate molecules involved in injured muscle, accelerating regeneration process.