Effects of low-level laser therapy after nerve reconstruction in rat denervated soleus muscle adaptation.
BACKGROUND
Peripheral nerve injury (PNI) rehabilitation remains a challenge for physical therapists because PNI effects are very disabling. Low-level laser therapy (LLLT) has been described as a physical resource that is able to influence enzymes called metallopeptidases (MMPs) associated with extracellular matrix (ECM) turnover, thus accelerating neuromuscular recovery after nerve crush injuries. However, the effects of LLLT in the treatment of severe nerve injuries and denervated slow-twitch muscles are still inconclusive.


OBJECTIVE
The aim of this study was to evaluate the effects of different wavelengths and energy densities of LLLT irradiation, applied to a severe nerve injury after reconstruction, on denervated slow-twitch skeletal muscle adaptation.


METHODS
Rats were submitted to a neurotmesis of the sciatic nerve followed by end-to-end neurorrhaphy. They received transcutaneous LLLT irradiation at the lesion site. The LLLT parameters were: wavelengths--660 or 780 nm; energy densities--10, 60 or 120 J/cm²; power--40 mW; spot--4 mm². Sciatic functional index (SFI), histological, morphometric, and zymographic analyses were performed. One-way ANOVA followed by Tukey's test was used (p≤0.05).


RESULTS
An atrophic pattern of muscle fibers was observed in all injured groups. The MMP activity in the soleus muscle reached normal levels. On the other hand, SFI remained below normality after PNI, indicating incapacity. No difference was found among PNI groups submitted or not to LLLT in any variable.


CONCLUSIONS
LLLT applied to the nerve post-reconstruction was ineffective in delaying degenerative changes to the slow-twitch denervated muscles and in functional recovery in rats. New studies on recovery of denervated slow-twitch muscle are necessary to support clinical practice.
Physical Therapy Department, Universidade Federal de São Carlos, São Carlos, SP, Brazil.
Marcela A
MA
Silva-Couto
Davilene
D
Gigo-Benato
Carla R
CR
Tim
Nivaldo A
NA
Parizotto
Tania F
TF
Salvini
Thiago L
TL
Russo
D000222:Adaptation, Physiological; D000818:Animals; D028022:Low-Level Light Therapy; D008297:Male; D009121:Muscle Denervation; D018482:Muscle, Skeletal / Q000294:innervation; D059348:Peripheral Nerve Injuries / Q000532:radiotherapy* / Q000601:surgery*; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function