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.

This study analyzed the effect of nandrolone decanoate (ND) on muscle repair and the expression of myogenic regulatory factors following cryoinjury in rat skeletal muscle. Adult male Wistar rats were randomly divided into 4 groups: control group, sham group, cryoinjured group treated with ND and non-injured group treated with ND. Treatment consisted of subcutaneous injections of ND (5 mg/kg) twice a week. After sacrifice, the tibialis anterior muscle was removed for the isolation of total RNA and analysis of myogenic regulatory factors using real-time PCR as well as morphological analysis using the hematoxylin-eosin assay. There was a significant increase in MyoD mRNA after 7 days and in myogenin mRNA after 21 days in the cryoinjured ND group in comparison to other groups in the same period. The morphological analysis revealed no edema or myonecrosis after 7 days as well as no edema or inflammatory infiltrate after 14 days in the cryoinjured ND group. In conclusion the anabolic steroid nandrolone decanoate can modulate the muscle repair process in rats following cryoinjury by influencing the expression of regulatory myogenic factors and phases of muscle repair.