Effect of low level laser (810 nm) on tendon tissue repair after tendinitis induction: molecular and biomechanical aspects

Abstract

Tendinitis are extremely common diseases, associated with a wide variety of treatments and therapies. Among them, laser therapy appears to be a promising alternative. Currently, the infrared laser is the wavelength that are most used, especially in the case of inflammatory joint diseases. Several studies have shown a significant anti-inflammatory effect of low level laser on the treatment of certain tissues such as tendons. The responsible mechanisms have not yet been fully elucidated. Nevertheless, some recent results show that this therapy leads to reduced gene expression of several inflammatory mediators such as PGE2, IL, and TNF, and causes an increase in the expression of other antiinflammatory mediators, such as IL-10. The laser can also reduce the expression of certain collagenases (MMPs) and consequently, reduce the degeneration of the tissue. It promotes the rearrangement of collagen fibers leading to an improvement in biomechanical properties of tendon, recorded during the repair process. Given the large impact of this disease on the worldwide population, and the low efficacy of currently therapies used, the development of new therapeutic alternatives is a challenge for Health Systems, especially in the context of developing countries. Moreover, the establishment of the rational and controlled clinical protocol of this technique is an inescapable problem in view of that laser therapy is commonly used empirically by healthcare professionals. We hypothesize that the low level laser (810 nm, infrared), may reduce the acute inflammatory process of the tendon, promoting tissue repair through inhibition of inflammatory mediators and collagenase (MMPs), contributing to improved mechanical properties.Objective: We intend to analyze quantitative and qualitative characteristics of the structure of collagen fibers in parallel with the evolution of mechanical properties of the tendon at the phenomenon of lesion, and after laser treatment.Methodology: The methodology based on the use of male rats (Wistar), which we divide into two groups: (1) injection of saline, and the group (2) tendinitis divided into two subgroups , treated with Diclofenac Sodium (groupe2.1) or the laser energy 1 Joule or 3 joules (group 2.2). Tendinitis is caused by injection of collagenase (100 mg / tendon) in the Achilles tendons. After 7 and 14 days, the animals are sacrificed and the tendons immediately taken and analyzed; - We will follow the changes in gene expression of collagenases MMP3, MMP9 and MMP13 and gene expression of collagens I and III by RT-PCR (real time); - Changes of collagen in the tissue will be evaluated by means of immunohistochemical technique; - We will proceed with the analysis of the directions of collagen fibers using the technique of birefringence by polarized light microscopy; - The mechanical properties of tendons in the different states, will be achieved through the use of an instrumented testing machine specially adapted. (AU)