Can photobiomodulation therapy be an alternative to pharmacological therapies in decreasing the progression of skeletal muscle impairments of mdx mice?

Abstract

Objective: To compare the effects of photobiomodulation therapy (PBMT) and pharmacological therapy (glucocorticoids and non-steroidal anti-inflammatory drugs) applied alone and in different combinations in mdx mice.

Methods: The animals were randomized and divided into seven experimental groups treated with placebo, PBMT, prednisone, non-steroidal anti-inflammatory drug (NSAIDs), PBMT plus prednisone and PBMT plus NSAID. Wild type animals were used as control. All treatments were performed during 14 consecutive weeks. Muscular morphology, protein expression of dystrophin and functional performance were assessed at the end of the last treatment.

Results: Both treatments with prednisone and PBMT applied alone or combined, were effective in preserving muscular morphology. In addition, the treatments with PBMT (p = 0.0005), PBMT plus prednisone (p = 0.0048) and PBMT plus NSAID (p = 0.0021) increased dystrophin gene expression compared to placebo-control group. However, in the functional performance the PBMT presented better results compared to glucocorticoids (p<0.0001). In contrast, the use of NSAIDs did not appear to add benefits to skeletal muscle tissue in mdx mice.

Conclusion: We believe that the promising and optimistic results about the PBMT in skeletal muscle of mdx mice may in the future contribute to this therapy to be considered a safe alternative for patients with Duchenne Muscular Dystrophy (DMD) in a washout period (between treatment periods with glucocorticoids), allowing them to remain receiving effective and safe treatment in this period, avoiding at this way periods without administration of any treatment.

Fig 1. Photomicrographs of histological muscles sections (longitudinal and transversal sections) of WT, placebo-control, PBMT, NSAID and Prednisone groups (HE, original magnification x 400).

Photomicrographs of WT and Placebo-control groups were obtained from a previous study [10].

Fig 2. Photomicrographs of histological muscles sections (longitudinal and transversal sections) of WT, placebo-control, PBMT + Prednisone and PBMT + NSAID groups (HE, original magnification x 400).

Photomicrographs of WT and Placebo-control groups were obtained from a previous study [10].

Fig 3. Histomorphometric analysis of all experimental groups.

The ^aaa indicates a significant difference compared with Placebo-control group (p<0.001), ^aaaa indicates a significant difference compared with Placebo-control group (p<0.0001), ^b indicates a significant difference compared with WT group (p<0.05), ^bb indicates a significant difference compared with WT group (p<0.01), ^bbbb indicates a significant difference compared with WT group (p<0.0001),), ^c indicates a significant difference compared with NSAID group (p<0.05), ^ccc indicates a significant difference compared with NSAID group (p<0.001), ^cccc indicates a significant difference compared with NSAID group (p<0.0001), ^ddd indicates a significant difference compared with PBMT + Prednisone group (p<0.001), ^dddd indicates a significant difference compared with PBMT + Prednisone group (p<0.0001), ^eeee indicates a significant difference compared with Prednisone group (p<0.0001), and ^ffff indicates a significant difference compared with PBMT + NSAID group (p<0.0001).

Fig 4. Protein expression of dystrophin in all experimental groups.

The *** indicates a significant difference compared with WT group (p<0.001), **** indicates a significant difference compared with WT group (p<0.0001), ^### indicates a significant difference compared with placebo group (p<0.001), ^#### indicates a significant difference compared with placebo group (p<0.0001), and ^ϕϕϕϕ indicates a significant difference compared with NSAID group (p<0.0001); n = 5 animals per group.

Fig 5. Functional performance assessment performed at baseline and post-treatment timepoints.

The * indicates a significant difference compared with all experimental groups at baseline (p<0.05), ** indicates a significant difference compared to placebo-control group at post-treatment evaluation (p<0.01), and **** indicates a significant difference compared with all experimental groups at baseline, and all the other experimental groups at post-treatment evaluation (p<0.0001); n = 5 animals per group.