Photobiomodulation and different macrophages phenotypes during muscle tissue repair.

Macrophages play a very important role in the conduction of several regenerative processes mainly due to their plasticity and multiple functions. In the muscle repair process, while M1 macrophages regulate the inflammatory and proliferative phases, M2 (anti-inflammatory) macrophages direct the differentiation and remodelling phases, leading to tissue regeneration. The aim of this study was to evaluate the effect of red and near infrared (NIR) photobiomodulation (PBM) on macrophage phenotypes and correlate these findings with the repair process following acute muscle injury. Wistar rats were divided into 4 groups: control; muscle injury; muscle injury + red PBM; and muscle injury + NIR PBM. After 2, 4 and 7 days, the tibialis anterior muscle was processed for analysis. Macrophages phenotypic profile was evaluated by immunohistochemistry and correlated with the different stages of the skeletal muscle repair by the qualitative and quantitative morphological analysis as well as by the evaluation of IL-6, TNF-α and TGF-ß mRNA expression. Photobiomodulation at both wavelengths was able to decrease the number of CD68+ (M1) macrophages 2 days after muscle injury and increase the number of CD163+ (M2) macrophages 7 days after injury. However, only NIR treatment was able to increase the number of CD206+ M2 macrophages (Day 2) and TGF-ß mRNA expression (Day 2, 4 and 7), favouring the repair process more expressivelly. Treatment with PBM was able to modulate the inflammation phase, optimize the transition from the inflammatory to the regeneration phase (mainly with NIR light) and improve the final step of regeneration, enhancing tissue repair.

Effect of low-level laser therapy on the modulation of the mitochondrial activity of macrophages / Efeito da laserterapia em baixa intensidade na modulação da atividade mitocondrial de macrófagos

BACKGROUND: Macrophages play a major role among the inflammatory cells that invade muscle tissue following an injury. Low-level laser therapy (LLLT) has long been used in clinical practice to accelerate the muscle repair process. However, little is known regarding its effect on macrophages. OBJECTIVE: This study evaluated the effect of LLLT on the mitochondrial activity (MA) of macrophages. METHOD: J774 macrophages were treated with lipopolysaccharide (LPS) and interferon - gamma (IFN-γ) (activation) for 24 h to simulate an inflammatory process, then irradiated with LLLT using two sets of parameters (780 nm; 70 mW; 3 J/cm2 and 660 nm; 15 mW; 7.5 J/cm2). Non-activated/non-irradiated cells composed the control group. MA was evaluated by the cell mitochondrial activity (MTT) assay (after 1, 3 and 5 days) in three independent experiments. The data were analyzed statistically. RESULTS: After 1 day of culture, activated and 780 nm irradiated macrophages showed lower MA than activated macrophages, but activated and 660 nm irradiated macrophages showed MA similar to activated cells. After 3 days, activated and irradiated (660 nm and 780 nm) macrophages showed greater MA than activated macrophages, and after 5 days, the activated and irradiated (660 nm and 780 nm) macrophages showed similar MA to the activated macrophages. CONCLUSIONS: These results show that 660 nm and 780 nm LLLT can modulate the cellular activation status of macrophages in inflammation, highlighting the importance of this resource and of the correct determination of its parameters in the repair process of skeletal muscle. .

CONTEXTUALIZAÇÃO: O macrófago tem papel de destaque dentre as células inflamatórias que invadem o músculo após as lesões. Por outro lado, o laser em baixa intensidade (LBI) tem sido muito utilizado na clínica para acelerar o reparo muscular, e pouco se conhece sobre seu efeito nos macrófagos. OBJETIVO: Avaliar o efeito do LBI sobre a atividade mitocondrial (AM) de macrófagos ativados para simular um processo inflamatório. MÉTODO: Macrófagos J774 foram tratados com lipopolissacarídeo (LPS) e IFN-gamma (ativação) por 24 horas para simular um processo inflamatório e então foram irradiados com LBI (780 nm; 70 mW; 3 J/cm(2) e 660 nm; 15mW; 7,5 J/cm(2)). A AM foi avaliada pela técnica MTT após um, três e cinco dias das irradiações. Foram realizados três experimentos independentes, e os dados, submetidos à análise estatística. RESULTADOS: Após um dia de cultivo, os macrófagos ativados e irradiados com o laser de 780 nm mostraram AM menor que os somente ativados, já os macrófagos ativados e irradiados com o laser de 660 mostraram AM semelhante aos somente ativados. Após três dias, os macrófagos ativados e irradiados (660 e 780 nm) mostraram AM maior que os macrófagos ativados; já após cinco dias, os grupos ativados e irradiados (660 e 780 nm) mostraram AM semelhante aos macrófagos somente ativados. CONCLUSÕES: Esses resultados mostram que tanto o LBI de 660 nm como o de 780 nm são capazes de modular a ativação celular de macrófagos em situação de inflamação, ressaltando a importância desse recurso e da determinação de seus parâmetros dosimétricos no processo de reparo do músculo esquelético. .

Effect of low-level laser therapy on the modulation of the mitochondrial activity of macrophages.

BACKGROUND: Macrophages play a major role among the inflammatory cells that invade muscle tissue following an injury. Low-level laser therapy (LLLT) has long been used in clinical practice to accelerate the muscle repair process. However, little is known regarding its effect on macrophages. OBJECTIVE: This study evaluated the effect of LLLT on the mitochondrial activity (MA) of macrophages. METHOD: J774 macrophages were treated with lipopolysaccharide (LPS) and interferon - gamma (IFN-γ) (activation) for 24 h to simulate an inflammatory process, then irradiated with LLLT using two sets of parameters (780 nm; 70 mW; 3 J/cm2 and 660 nm; 15 mW; 7.5 J/cm2). Non-activated/non-irradiated cells composed the control group. MA was evaluated by the cell mitochondrial activity (MTT) assay (after 1, 3 and 5 days) in three independent experiments. The data were analyzed statistically. RESULTS: After 1 day of culture, activated and 780 nm irradiated macrophages showed lower MA than activated macrophages, but activated and 660 nm irradiated macrophages showed MA similar to activated cells. After 3 days, activated and irradiated (660 nm and 780 nm) macrophages showed greater MA than activated macrophages, and after 5 days, the activated and irradiated (660 nm and 780 nm) macrophages showed similar MA to the activated macrophages. CONCLUSIONS: These results show that 660 nm and 780 nm LLLT can modulate the cellular activation status of macrophages in inflammation, highlighting the importance of this resource and of the correct determination of its parameters in the repair process of skeletal muscle.

No effect of low-level lasers on in vitro myoblast culture.

Effects of phototherapy using low-level lasers depend on irradiation parameters and the type of laser used. The aim of the present study was to evaluate the effect of phototherapy on the proliferation of cultured C2C12 myoblasts under different nutritional conditions using low-level GaAlAs and InGaAlP lasers with different parameters and incubation periods. C2C12 cells cultured in regular and nutrient-deficient medium were irradiated with low-level GaAlAs (780 nm) and InGaA1P (660 nm) lasers with energy densities of 3.8, 6.3 and 10 J/cm2, and 3.8, 10 and 17.5 J/cm2, respectively. Cell proliferation was assessed 48 and 72 h after irradiation by MTT assay. There were no significant differences in cell proliferation between laser-treated myoblasts and control cultures for any of the parameters and incubation periods. Further studies are necessary to determine the correct laser parameters for optimizing the biostirhulation of myoblasts.