Time-dependent effects of low-level laser therapy on the morphology and oxidative response in the skin wound healing in rats

Abstract

This study aims to investigate the effect of different energy densities provided by low-level laser therapy (LLLT) on the morphology of scar tissue and the oxidative response in the healing of secondary intention skin wounds in rats. Twenty-four male adult Wistar rats were used. Skin wounds were made on the backs of the animals, which were randomized into three groups of eight animals each as follows, 0.9% saline (control); laser GaAsAl 30 J/cm(2) (L30); laser GaAsAl 90 J/cm(2) (L90). The experiment lasted 21 days. Every 7 days, the wound contraction index (WCI) was calculated and tissue from different wounds was removed to assess the proportion of cells and blood vessels, collagen maturation index (CMI), thiobarbituric acid reactive substance (TBARS) levels and catalase activity (CAT). On the 7th and 14th days, the WCI and the proportion of cells were significantly higher in groups L30 and L90 compared to the control (p < 0.05). At all the time points analyzed, there was a greater proportion of blood vessels and a higher CMI in group L90 compared to the other groups (p < 0.05). On the 7th and 14th days, lower TBARS levels and increased CAT activity were found in the L90 group compared to the control (p < 0.05). On the 7th day, a moderately negative correlation was found between TBARS levels and WCI, CMI and CAT in all the groups. LLLT may modulate the oxidative status of wounded tissue, constituting a possible mechanism through which the LLLT exerts its effects in the initial phases of tissue repair.

Effects of 660 nm low-level laser therapy on muscle healing process after cryolesion

“…Vascular photomodulation can be associated with the reduction of inflammatory cells and stimulation of macrophages, Tlymphocytes, endothelial cells, and fibroblast migration during the healing process, resulting in accelerated tissue healing [38]. Gonçalves et al showed that the GaAsAl laser applied with an energy density of 60 J/cm 2 was more effective in stimulating neoangiogenesis than 30 J/cm 2 [37]. Furthermore, Corazza et al reported that a dose of 20 J/cm 2 effectively increased fibroblast proliferation and neoangiogenesis in skin wounds [39].…”

“…An adequate blood perfusion is essential to guarantee injured tissue regeneration and, consequently, the success of the repair procedure [37]. Vascular photomodulation can be associated with the reduction of inflammatory cells and stimulation of macrophages, Tlymphocytes, endothelial cells, and fibroblast migration during the healing process, resulting in accelerated tissue healing [38].…”

Proposed Mechanisms of Photobiomodulation or Low-Level Light Therapy

“…The balance between oxidants and antioxidants is directly related to the time and quality of the wound healing process[127]. This process can be divided in four overlapping phases: hemostasis, inflammation, proliferation and remodeling or resolution.…”

A Quantitative Study of the Relationship between the Distribution of Different Types of Collagen and the Mechanical Behavior of Rabbit Medial Collateral Ligaments

“…The picrosirius red staining-polarization method can distinguish and determine the level of types I and III collagen and has been used for many tissues, such as skin [34], [35], lung [36], cartilage [37], periodontal ligament [38], vocal ligament [39], and tendon [19], [40]. As described in our previous study [18], the type I and III collagen contents in the mid-substance of the ligament were determined by this method.…”