Effect of photobiomodulation on connective tissue remodeling and regeneration of skeletal muscle in elderly rats
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The purpose of this study was to evaluate the effects of low-level laser therapy (LLLT) on morphological aspects, IL-6 and IL-1β expressions, as well as the distribution and organization of collagen in the tibialis anterior (TA) muscle of elderly rats submitted to cryoinjury. Histological photomicrographs were taken of TA muscles stained with HE and picrosirius red. Immunohistochemistry was used for the evaluation of IL-6 and IL-1β. Male Wistar rats, aged 20 months, were distributed into three groups: (1) control animals not injured or treated with LLLT (n = 5), (2) cryoinjury without LLLT treatment (n = 15), and (3) cryoinjury treated with infrared LLLT (n = 15). LLLT was applied to the TA 2 h after of the injury induction and consisted of daily applications until the sacrifice (1, 3, and 7 days). The following parameters were used: λ = 780 nm, power density 1 W/cm2, output power 40 mW, 10 s per point, 8 points, and 3.2 J of total energy. In the histomorphological analysis, the treated group exhibited a significant decrease in inflammatory infiltrate (p < 0.001) as well as an increase immature fibers and new blood vessels at 7 days compared to the untreated group (p < 0.05). Furthermore, treatment induced a better collagen distribution and organization at 7 days in comparison to the untreated group (p < 0.05). In conclusion, LLLT demonstrated a modulatory effect on the muscle repair process in elderly animals with regard to the collagen remodeling and morphological aspects of muscle tissue.
KeywordsAging Regeneration Low-level laser therapy LLLT Collagen Skeletal muscle
This work was supported by UNINOVE and the following Brazilian fostering agencies: Conselho Nacional de Desenvolvimento Científico e Tecnológico (www.cnpq.br; process number: 305739/2014 RAMF, 311078/2015-0 KPSF, 305905/2014-7 SKB), Coordenação de Aperfeiçoamento de Pessoal do Nível Superior (www.capes.gov.br; process numbers: 1510536 BGR), and Fundação de Amparo à Pesquisa do Estado de São Paulo (www.fapesp.br; process number: 2014/12381-1 RAMF).
Compliance with ethical standards
This study was developed at the research laboratory of the Postgraduate Program in Biophotonics Applied to Health Sciences using a methodology in accordance with international ethical standards for animal experimentation (National Research Council, 1996).
Conflict of interest
The authors declare that they have no conflict of interest.
Ethical approval and informed consent
The protocol of this study plan was approved by the Ethics Committee for Animal Research of University Nove de Julho (no. An0002/2014). This study does not include human participants.
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