title: LLLT improves tendon healing through increase of MMP activity and collagen synthesis.
abstract: The Achilles tendon has a high incidence of rupture, and the healing process leads to a disorganized extracellular matrix (ECM) with a high rate of injury recurrence. To evaluate the effects of different conditions of low-level laser (LLL) application on partially tenotomized tendons, adult male rats were divided into the following groups: G1, intact; G2, injured; G3, injured + LLL therapy (LLLT; 4 J/cm(2) continuous); G4, injured + LLLT (4 J/cm(2), 20 Hz); G5, injured; G6, injured + LLLT (4 J/cm(2) continuous); and G7, injured + LLLT (4 J/cm(2), 20 Hz until the 7th day and 2 kHz from 8 to 14 days). G2, G3, and G4 were euthanized 8 days after injury, and G5, G6, and G7 were euthanized on the 15th day. The quantification of hydroxyproline (HOPro) and non-collagenous protein (NCP), zymography for matrix metalloproteinase (MMP)-2 and MMP-9, and Western blotting (WB) for collagen types I and III were performed. HOPro levels showed a significant decrease in all groups (except G7) when compared with G1. The NCP level increased in all transected groups. WB for collagen type I showed an increase in G4 and G7. For collagen type III, G4 presented a higher value than G2. Zymography for MMP-2 indicated high values in G4 and G7. MMP-9 increased in both treatment groups euthanized at 8 days, especially in G4. Our results indicate that the pulsed LLLT improved the remodeling of the ECM during the healing process in tendons through activation of MMP-2 and stimulation of collagen synthesis.
authors.affiliation: Department of Anatomy, Cell Biology and Physiology and Biophysics, Institute of Biology, University of Campinas-UNICAMP, CP 6109, Campinas, São Paulo, 13083-970, Brazil. dgflavia@yahoo.com.br
authors.forename: Flávia Da Ré
authors.initials: Fda R
authors.lastname: Guerra
authors.forename: Cristiano Pedrozo
authors.initials: CP
authors.lastname: Vieira
authors.forename: Marcos Santos
authors.initials: MS
authors.lastname: Almeida
authors.forename: Letícia Prado
authors.initials: LP
authors.lastname: Oliveira
authors.forename: Andrea Aparecida
authors.initials: AA
authors.lastname: de Aro
authors.forename: Edson Rosa
authors.initials: ER
authors.lastname: Pimentel
mesh_terms: D000125:Achilles Tendon / Q000293:injuries* / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D003094:Collagen / Q000096:biosynthesis*; D024042:Collagen Type I / Q000096:biosynthesis; D024061:Collagen Type III / Q000096:biosynthesis; D004195:Disease Models, Animal; D006909:Hydroxyproline / Q000378:metabolism; D054023:Lasers, Semiconductor / Q000627:therapeutic use; D028022:Low-Level Light Therapy; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012421:Rupture / Q000378:metabolism / Q000532:radiotherapy; D013708:Tendon Injuries / Q000378:metabolism* / Q000532:radiotherapy*; D014945:Wound Healing / Q000528:radiation effects*
chemical_list: D024042:Collagen Type I; D024061:Collagen Type III; D003094:Collagen; D020778:Matrix Metalloproteinase 2; C522363:Mmp2 protein, rat; D020780:Matrix Metalloproteinase 9; C572337:Mmp9 protein, rat; D006909:Hydroxyproline