Influence of laser photobiomodulation on collagen IV during skeletal muscle tissue remodeling after injury in rats.
OBJECTIVE
The aim of the present study was to determine the effect of GaAlAs low-level laser therapy (LLLT) on collagen IV remodeling of the tibialis anterior (TA) muscle in rats after cryolesion.


BACKGROUND
Considerable interest exists in skeletal muscle regeneration in situations such as repair after exercise-induced muscle injury, after muscle transplantation, in muscular dystrophy, exercise-induced muscle injury, and the recovery of strength after atrophy due to disuse. A number of studies have demonstrated the potential of LLLT in facilitating the muscle-healing process; however, no consensus is found in the literature regarding the best laser-irradiation parameters.


METHODS
Adult male Wistar rats (n = 45) were used and randomly divided into three groups: control (n = 5); nontreated cryolesioned group (n = 20), and LLLT-cryolesioned group (n = 20). The cryolesioned groups were analyzed at 1, 7, 14, and 21 days after the injury procedure. Laser irradiation was performed 3 times per week on the injured region by using the GaAlAs laser (660 nm; beam spot of 0.04 cm(2), output power of 20 mW, power density of 500 mW/cm(2), and energy density of 5 J/cm(2), for 10 sec). The muscles were removed, frozen, cryosectioned, and then stained with hematoxylin-eosin for the visualization of general morphology or used for immunohistochemical analysis of collagen IV.


RESULTS
It was demonstrated that LLLT promotes an increase in collagen IV immunolabeling in skeletal muscle in the first 7 days after acute trauma caused by cryoinjury, but does not modify the duration of the tissue-repair process. Even with LLLT, the injured muscle tissue needs ∼21 days to achieve the same state of organization as that in the noninjured muscle.


CONCLUSIONS
The collagen IV content is modulated in regenerating skeletal muscle under LLLT, which might be associated with better tissue outcome, although the histologic analysis did not detect tissue improvement in the LLLT group.
Baptista
Juliana
J
Universidade Nove de Julho- UNINOVE, São Paulo, Brazil.
Martins
Manoela Domingues
MD
Pavesi
Vanessa Christina Santos
VC
Bussadori
Sandra Kalil
SK
Fernandes
Kristianne Porta Santos
KP
Pinto Júnior
Décio dos Santos
Ddos S
Ferrari
Raquel Agnelli Mesquita
RA
D000818:Animals; D024141:Collagen Type IV / Q000032:analysis*; D007150:Immunohistochemistry; D028022:Low-Level Light Therapy; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries* / Q000528:radiation effects*; D051381:Rats; D017208:Rats, Wistar; D012038:Regeneration / Q000502:physiology / Q000528:radiation effects*; D014945:Wound Healing / Q000502:physiology / Q000528:radiation effects
D024141:Collagen Type IV