Low-level laser therapy in collagenase-induced achilles tendinitis in rats: Analyses of biochemical and biomechanical aspects
Marcos RL, Leal-Junior EC, Arnold G, Magnenet V, Rahouadj R, Wang X, Demeurie F, Magdalou J, de Carvalho MH, Lopes-Martins RA. J Orthop Res. 2012 Jun 5. doi: 10.1002/jor.22156. [Epub ahead of print]
Achilles tendinopathy is a common injury among both competitive and recreational athletes. This injury is commonly treated with non-steroidal anti-inflammatory drugs (NSAIDs) and various rehabilitation strategies. Low-level laser therapy (LLLT) has recently been shown to have success treating several overuse injuries. However, the underlying mechanisms involved in the improvement of symptoms following LLLT treatment in tendinopathy are poorly understood. Therefore, the purpose of this study was to examine the short term biochemical mechanisms following LLLT treatment in a chemically (collagenase) induced tendinitis. Thirty-six Wistar rats were divided into 6 experimental groups: 1) control group 2) collagenase-induced tendinopathy with 1 Joule (J) LLLT examined acutely, 3) collagenase-induced tendinopathy with 3J LLLT examined acutely 4) collagenase-induced tendinopathy with 1J LLLT examined a week later 5) collagenase-induced tendinopathy with 3J LLLT examined a week later 6) sodium diclofenac. The control rats were injected under anesthesia with a control solution. The collagenase groups were all injected with a local dose of collagenase to the Achilles tendon then received a single treatment of LLLT 1 hour after injection with either 1 or 3Js of energy. The sodium diclofenac group was received the NSAID 30 minutes prior to the collagenase injection. Following completion of the study tissue was harvested and prepared for RT-PCR (measure of gene expression), ELISA (measure of protein content), and tendon mechanical testing. The gene expression was examined for several pro-inflammatory (COX-2 and TNF-α) and degradation (MMP-3, -9, and -13) factors. Protein content was examined for prostaglandin E2 (an inflammatory mediator). Mechanical properties were also tested on isolated Achilles tendon using a cyclic fatigue protocol until failure and the maximal force was reported. They found that collagenase increased expression of all biochemical markers examined compared to control. LLLT at 1J significantly lowered the gene expression in all genes except COX-2 and MMP-3. LLLT at 3J significantly lowered the gene expression in all genes. Sodium diclofenac only lowered the protein content of prostaglandin E2. The mechanical properties were lowered in the collagenase and sodium diclofenac groups compared to control. Both LLLT at 1 and 3J improved the mechanical properties at 7 days; however the 1J group demonstrated even better results. The sodium diclofenac group also had higher mechanical properties compared to the collagenase group but where lower compared to the other treatment groups.
This study examined the underlying biochemical mechanisms involved in a short duration treatment of LLLT following a chemically-induced tendinitis. It is important to identify the physiologic mechanisms involved in therapeutic modalities in addition to the structural benefits. This information allows clinicians to manipulate the application of this modality to optimize treatment outcomes. Although there were significant differences in inflammatory and catabolic genes and proteins across the injury groups this study only examined the initial stages of the inflammatory process and did not evaluate the full duration of healing. This study may be on par with providing LLLT over a tendon in the very early phases of tendinopathy. Although there were significant differences at these early time points the most desired information is the final endpoint. In addition, the decreased expression of the inflammatory and degradation factors may seem ideal, but these factors are required to heal injured tissue. It will be interesting to see the influence of LLLT with repetitive treatments as the tendon recovers and to see more randomized controlled studies in humans. Therefore the optimal level of the biochemical response following injury is currently not known. Based on these results would you recommend this treatment for tendinopathy? Have you seen long term beneficial effects following LLLT?
Written by: Stephen Thomas
Reviewed by: Jeffrey Driban
Related Posts:Marcos RL, Leal-Junior EC, Arnold G, Magnenet V, Rahouadj R, Wang X, Demeurie F, Magdalou J, de Carvalho MH, & Lopes-Martins RA (2012). Low-level laser therapy in collagenase-induced achilles tendinitis in rats: Analyses of biochemical and biomechanical aspects. Journal of Orthopaedic Research PMID: 22674405