LLLT improves tendon healing through increase of MMP activity and collagen synthesis

• Published in: Lasers in medical science Vol. 28; no. 5; pp. 1281 - 1288
• Main Authors: Guerra, Flávia Da Ré, Vieira, Cristiano Pedrozo, Almeida, Marcos Santos, Oliveira, Letícia Prado, de Aro, Andrea Aparecida, Pimentel, Edson Rosa
• Format: Journal Article
• Language: English
• Published: London Springer London 01.09.2013; Springer Nature B.V
• Subjects: Achilles Tendon - injuries; Achilles Tendon - metabolism; Achilles Tendon - radiation effects; Animals; Collagen; Collagen - biosynthesis; Collagen Type I - biosynthesis; Collagen Type III - biosynthesis; Dentistry; Disease Models, Animal; Euthanasia; Hydroxyproline - metabolism; Lasers; Lasers, Semiconductor - therapeutic use; Low-Level Light Therapy; Male; Matrix Metalloproteinase 2 - metabolism; Matrix Metalloproteinase 9 - metabolism; Medicine; Medicine & Public Health; Optical Devices; Optics; Original Article; Photonics; Quantum Optics; Rats; Rats, Wistar; Rupture - metabolism; Rupture - radiotherapy; Tendon Injuries - metabolism; Tendon Injuries - radiotherapy; Tendons; Wound Healing - radiation effects; Achilles tendon; Matrix metalloproteinase 2; Matrix metalloproteinase 9; LLLT; Collagen; Rupture
• ISSN: 0268-8921; 1435-604X
• DOI: 10.1007/s10103-012-1236-7

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.