Low power infrared laser in pulsed emission mode modulates mRNA levels from pro-inflammatory and anti-inflammatory cytokines favoring repair process in injured muscle

Muscle injury healing is a complex and dynamic process characterized by different phases with the purpose of restoring muscular function. Inflammation occurs within the first 5 d after injury and during this process the release of pro-inflammatory and anti-inflammatory cytokines such as IL-6, IL-1β, IL-4 and IL-10 occurs. It has recently been shown that these cytokines play an important role in muscle injury repair. Thus, this study evaluated the mRNA levels from pro-inflammatory and anti-inflammatory cytokine genes in injured tibial anterior muscle from Wistar rats exposed to low power infrared laser. Cryoinjury was used as model of muscle injury. Low power infrared laser was used in pulsed emission mode according to the manufacturer's recommendations (25 mW or 75 mW, 0.5 J, 904 nm, 3 J cm−2). Animals were divided into three groups: injured group (n = 5), injured and irradiated group at 25 mW (n = 5) and injured and irradiated group at 75 mW (n = 5). Laser irradiations were for five consecutive days after injury and euthanasia occurred on the fifth day after injury for morphological analysis and mRNA level evaluation by RT-qPCR. Our results showed that laser modulates the mRNA levels from pro-inflammatory (IL-6 and IL-1β) as well as the anti-inflammatory (IL-4) cytokine gene. IL-10 mRNA was not observed in any of the analyzed groups. In conclusion, laser exposure modulates the mRNA levels from pro-inflammatory and anti-inflammatory cytokine genes during the muscle repair process and this can be one of the beneficial effects of low power lasers that favor muscle repair process.