title: GaAs 904-nm laser irradiation improves myofiber mass recovery during regeneration of skeletal muscle previously damaged by crotoxin.
abstract: This work investigated the effect of gallium arsenide (GaAs) irradiation (power: 5 mW; intensity: 77.14 mW/cm(2), spot: 0.07 cm(2)) on regenerating skeletal muscles damaged by crotoxin (CTX). Male C57Bl6 mice were divided into six groups (n = 5 each): control, treated only with laser at doses of 1.5 J or 3 J, CTX-injured and, CTX-injured and treated with laser at doses of 1.5 J or 3 J. The injured groups received a CTX injection into the tibialis anterior (TA) muscle. After 3 days, TA muscles were submitted to GaAs irradiation at doses of 1.5 or 3 J (once a day, during 5 days) and were killed on the eighth day. Muscle histological sections were stained with hematoxylin and eosin (H&E) in order to determine the myofiber cross-sectional area (CSA), the previously injured muscle area (PIMA) and the area density of connective tissue. The gene expression of MyoD and myogenin was detected by real-time PCR. GaAs laser at a dose of 3 J, but not 1.5 J, significantly increased the CSA of regenerating myofibers and reduced the PIMA and the area density of intramuscular connective tissue of CTX-injured muscles. MyoD gene expression increased in the injured group treated with GaAs laser at a dose of 1.5 J. The CTX-injured, 3-J GaAs laser-treated, and the CTX-injured and treated with 3-J laser groups showed an increase in myogenin gene expression when compared to the control group. Our results suggest that GaAs laser treatment at a dose of 3 J improves skeletal muscle regeneration by accelerating the recovery of myofiber mass.
authors.affiliation: Department of Anatomy, Biomedical Sciences Institute, University of São Paulo, Lineu Prestes Av., 2415, 05508-000, São Paulo, SP, Brazil.
authors.forename: Lucila H
authors.initials: LH
authors.lastname: Silva
authors.forename: Meiricris T
authors.initials: MT
authors.lastname: Silva
authors.forename: Rita M
authors.initials: RM
authors.lastname: Gutierrez
authors.forename: Talita C
authors.initials: TC
authors.lastname: Conte
authors.forename: Cláudio A
authors.initials: CA
authors.lastname: Toledo
authors.forename: Marcelo S
authors.initials: MS
authors.lastname: Aoki
authors.forename: Richard E
authors.initials: RE
authors.lastname: Liebano
authors.forename: Elen H
authors.initials: EH
authors.lastname: Miyabara
mesh_terms: D000818:Animals; D003439:Crotoxin / Q000633:toxicity; D015870:Gene Expression / Q000528:radiation effects; D054023:Lasers, Semiconductor / Q000627:therapeutic use*; D028022:Low-Level Light Therapy; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000187:drug effects / Q000293:injuries / Q000502:physiology* / Q000528:radiation effects*; D018008:Myogenin / Q000235:genetics; D012038:Regeneration / Q000235:genetics / Q000502:physiology / Q000528:radiation effects*
chemical_list: C503801:Myog protein, mouse; D018008:Myogenin; D003439:Crotoxin