Effects of low-level laser therapy on expression of TNF-α and TGF-β in skeletal muscle during the repair process

Abstract

The aim of the present study was to determine the effect of low-level laser therapy (LLLT) on the expression of TNF-α and TGF-β in the tibialis anterior muscle of rats following cryoinjury. Muscle regeneration involves cell proliferation, migration and differentiation and is regulated by growth factors and cytokines. A growing body of evidence suggests that LLLT promotes skeletal muscle regeneration by reducing the duration of acute inflammation and accelerating tissue repair. Adult male Wistar rats (n = 35) were randomly divided into three groups: control group (no lesion, untreated, n = 5), cryoinjury without LLLT group (n = 15), and cryoinjury with LLLT group (n = 15). The injured region was irradiated three times a week using an AlGaInP laser (660 nm; beam spot 0.04 cm(2), output power 20 mW, power density 500 mW/cm(2), energy density 5 J/cm(2), exposure time 10 s). Muscle remodeling was evaluated at 1, 7 and 14 days (long-term) following injury. The muscles were removed and total RNA was isolated using TRIzol reagent and cDNA synthesis. Real-time polymerase chain reactions were performed using TNF-α and TGF-β primers; GAPDH was used to normalize the data. LLLT caused a decrease in TNF-α mRNA expression at 1 and 7 days following injury and in TGF-β mRNA expression at 7 days following cryoinjury in comparison to the control group. LLLT modulated cytokine expression during short-term muscle remodeling, inducing a decrease in TNF-α and TGF-β.

Photobiomodulation and different macrophages phenotypes during muscle tissue repair

“…Using PBM at 660 nm (20 mW and 1.6 J) with the same experimental model, De Souza et al12 and Mesquita‐Ferrari et al16 also found a reduction in myonecrosis at 7 days as well as a reduction in TNF‐ α mRNA expression after 1 and 7 days. TNF‐ α is a proinflammatory cytokine that stimulates myogenic cell proliferation, but also inhibits its differentiation and fusion 3, 24.…”

“…Cryoinjury, which can be considered an acute injury1, 12, 13, 16, 17, 21 provoked myonecrosis and the infiltration of inflammatory cells in the injured area on Day 2. A large number of CD68 + macrophages (M1) and small number of CD206 + and CD163 + (M2) macrophages were also found 2 days after injury, which is in accordance with previous descriptions (for review, see1).…”

“…The cryoinjury procedure was performed using a previously described method 16, 18. The surgical procedures were performed under anesthesia with 10% ketamine HCl (Dopalen; Vetbrands, São Paulo, Brazil) and 2% xylazine (Anasedan; Vetbrands) (100 and 10 mg/kg, respectively).…”

“…The laser beam was applied in contact with the skin surface over the cryoinjury area at an angle of 90° between the emitter and skin to prevent reflection. Irradiation was applied to 8 points (Figure S2B) surrounding the sutured area 12, 16, 17, 18. After 2, 4 and 7 days of treatment, the animals were weighed and euthanized with an overdose of anesthesia (240 mg/kg of ketamine and 30 mg/kg of xylazine).…”

“…In a time‐dependent manner, red and NIR therapies are also able to modulate the gene expression of mediators, such as TNF‐ α , 15, 16 IL1‐ β , 17 IL‐6 18 and TGF‐ β16, 19 as well as genes involved in the differentiation of myogenic stem cells, such as MyoD 18, 20 and myogenin 18, 20 during the muscle repair process.…”