Effects of 660 and 780 nm low-level laser therapy on neuromuscular recovery after crush injury in rat sciatic nerve.
OBJECTIVE
Post-traumatic nerve repair is still a challenge for rehabilitation. It is particularly important to develop clinical protocols to enhance nerve regeneration. The present study investigated the effects of 660 and 780 nm low-level laser therapy (LLLT) using different energy densities (10, 60, and 120 J/cm²) on neuromuscular and functional recovery as well as on matrix metalloproteinase (MMP) activity after crush injury in rat sciatic nerve.


METHODS
Rats received transcutaneous LLLT irradiation at the lesion site for 10 consecutive days post-injury and were sacrificed 28 days after injury. Both the sciatic nerve and tibialis anterior muscles were analyzed. Nerve analyses consisted of histology (light microscopy) and measurements of myelin, axon, and nerve fiber cross-sectional area (CSA). S-100 labeling was used to identify myelin sheath and Schwann cells. Muscle fiber CSA and zymography were carried out to assess the degree of muscle atrophy and MMP activity, respectively. Statistical significance was set at 5% (P≤0.05).


RESULTS
Six hundred sixty nanometer LLLT either using 10 or 60 J/cm² restored muscle fiber, myelin and nerve fiber CSA compared to the normal group (N). Furthermore, it increased MMP-2 activity in nerve and decreased MMP-2 activity in muscle and MMP-9 activity in nerve. In contrast, 780 nm LLLT using 10 J/cm² decreased MMP-9 activity in nerve compared to the crush group (CR) and N; it also restored normal levels of myelin and nerve fiber CSA. Both 60 and 120 J/cm² decreased MMP-2 activity in muscle compared to CR and N. 780 nm did not prevent muscle fiber atrophy. Functional recovery in the irradiated groups did not differ from the non-irradiated CR.


CONCLUSIONS
Data suggest that 660 nm LLLT with low (10 J/cm²) or moderate (60 J/cm²) energy densities is able to accelerate neuromuscular recovery after nerve crush injury in rats.
Gigo-Benato
Davilene
D
Thermophototherapy Unit, Physical Therapy Department, Federal University of São Carlos (UFSCar), São Carlos, SP13565-905, Brazil. benatodavilene@yahoo.com.br
Russo
Thiago Luiz
TL
Tanaka
Erika Harumi
EH
Assis
Lívia
L
Salvini
Tania Fátima
TF
Parizotto
Nivaldo Antonio
NA
D000818:Animals; D054023:Lasers, Semiconductor / Q000627:therapeutic use*; D028022:Low-Level Light Therapy; D008297:Male; D009409:Nerve Crush; D009416:Nerve Regeneration / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function / Q000528:radiation effects*; D012584:Sciatic Nerve / Q000293:injuries* / Q000502:physiology / Q000528:radiation effects; D020426:Sciatic Neuropathy / Q000209:etiology / Q000503:physiopathology / Q000532:radiotherapy*