Avaliação e comparação de diferentes comprimentos de onda (660 e 808 NM) da terapia por fotobiomodulação a laser na atrofia muscular em modelo de imobilização em ratos
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Data
2021
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Universidade Brasil
Resumo
Atrophy of skeletal striated muscle tissue is a complex process caused by an imbalance
between the degradation and synthesis of myofibrillar proteins, leading to a reduction in
muscle strength and the quality of life individuals. Considerable efforts have been
devoted to establish new treatments for an effective and safe clinical for treatment of
muscle atrophy. Among the available therapeutic resources, photobiomodulation
therapy (PBMT) has great potential, as it is often used as a promising therapeutic
strategy for the rehabilitation of skeletal striated muscle tissue, however, there is no
consensus on the best parameters in the treatment of muscle atrophy. Thus, the aim of
the present study was to evaluate the in vivo response of PBMT to laser at red and
infrared wavelengths in muscle atrophy in an immobilization model in rats. 32 male
Wistar rats were used, divided into 4 groups (n = 8): control group (C); Immobilized group
(ImC); Immobilized group submitted to PBMT laser at red wavelength (ImR); Immobilized
group submitted to laser PBMT at the infrared wavelength (ImIR). The left hind limb was
immobilized in extension for 5 days. For laser PBMT, equipment was used (λ = 660 and
808 nm; P = 30 mW; t = 47 s; D = 50 J/cm²) applied at two points in the gastrocnemius
muscle (cranial and caudal). Treatments started immediately after removal of the
immobilization, with 24-hour intervals, totaling 9 sessions. To evaluate and compare the
treatments, histological analysis were performed, as well as the profile area, cell density
and ATPase histochemistry. Histological results showed fibers of varied shape,
infiltration of inflammatory cells, and thickening of the connective tissue, reduced profile
and increased density of muscle fibers in all immobilized animals. Furthermore, it was
possible to verify a modulation of the inflammatory process and a lesser thickening of
the intramuscular connective tissue in both ImR and ImIR groups, however, these results
were more pronounced in the ImIR group, associated with morphological findings of
regenerating fibers and an increase in the number of fibers oxidative (type I fibers). Thus,
we can conclude that laser PBMT at both wavelengths were effective in changing the
morphology of the gastrocnemius muscle subjected to atrophy in an experimental
immobilization model, reducing the inflammatory infiltrate and the formation of
intramuscular connective tissue. However, RI promoted a more evident positive effect
by increasing regenerating muscle fibers and the number of oxidative fibers, which may
be a promising resource in the clinical treatment of muscle atrophy.
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Palavras-chave
Terapia de fotobiomodulação, Laser de baixa intensidade, Atrofia muscular, Imobilização