Phototherapy Improves Healing of Cutaneous Wounds in Nourished and Undernourished Wistar Rats

Abstract

A wound represents the interruption of the continuity of tissue that is followed by damage or cellular death. Wound healing occurs due to a competitive mechanism between the synthesis and lysis of collagen. Any factor that increases collagen lysis or reduces its synthesis may result in changes in the healing process, i.e., nutritional deficiencies. Phototherapies have been suggested as an effective method to improve wound healing. This study evaluated, histologically, the differences in the healing of cutaneous wounds in nourished and undernourished rats following laser therapy or illumination by polarized light. Fifty nourished or undernourished Wistar rats had a standardized wound created on the dorsum and were divided into 6 subgroups: Group 1 – Control (Standard diet; n=5); Group 2 – Control (DBR; n=5); Group 3 – Standard diet + laser therapy (λ635nm; 20J/cm2, n=5; or 40J/cm2, n=5); Group 4 – Standard diet + Bioptron® (λ400-2000nm; 20J/cm2, n=5; or 40 J/cm2, n=5); Group 5 – DBR + laser therapy (λ635nm; 20J/cm2, n=5; or 40J/cm2, n=5); Group 6 – DBR + Bioptron® (λ400-2000nm; 20J/cm2, n=5; or 40 J/cm2, n=5). The first application of the treatment was carried out immediately after surgery and repeated every 24 h during 7 days. Specimens were routinely processed (wax, cut and stained with H&E and Picrosirius stain) and analyzed under light microscopy. Analysis included re-epithelization, inflammatory infiltrate, and fibroblastic proliferation. Picrosirius stained slides were used to perform descriptive analysis of the collagen fibers. The results showed the best results for nourished and undernourished groups treated with polarized light at a dose of 20J/cm2 and the undernourished groups irradiated with the laser light. It is concluded that the nutritional status influenced the progression of the healing process as well as the quality of the healed tissue and that the use of both modalities of phototherapy resulted in a positive biomodulatory effect in both nourished and undernourished subjects. The effect of the polarized light was more evident in nourished subjects and laser therapy more effective in the treatment of undernourished subjects, in both cases with a dose of 20J/cm2.