Low-level laser therapy during postnatal development modulates degeneration and enhances regeneration processes in the hindlimb muscles of dystrophic mice

Abstract

Objective: The aim of the present study was to determine whether low-level laser therapy (LLLT) at early stages postpartum could affect regeneration and degenerative processes in skeletal muscles of the dystrophic mdx mouse.

Background data: LLLT has been found to modulate various biological processes. It was previously shown that LLLT can markedly promote the process of skeletal muscle regeneration and angiogenesis, as well as reduce apoptosis in skeletal muscle fibers in culture.

Methods and results: Eight newborn mdx mice were used. Ga-Al-As diode laser (810 nm) was applied at a power density of10 mW/cm(2) to the surface (area of 0.0255 cm(2)) of hindlimb muscle for 120 sec (fluence of 1.2 J/cm(2)) once a week for 4 consecutive weeks, commencing 1 week post-birth. The contralateral leg served as an untreated (sham) control. Mice were euthanized 2 days following the last laser application, and the muscles were processed for histology. Histological sections were scored for degenerative muscle foci. Statistical analysis revealed a score of 2.91±0.17 in the control, untreated group, which was significantly higher (p<0.001) than the value in the laser-treated group (1.56±0.49), indicating less degenerative foci in the laser-treated muscles. Histology also indicated regeneration (numerous myotubes) in the laser-treated mice, and no regeneration in the non-laser-treated mice.

Conclusions: The results indicate that LLLT applied to mdx mice during postnatal development may have a significant beneficial effect in the induction of regenerative capacity and reduction of degenerative muscle foci in these mice, with possible direct clinical relevance.