Photobiomodulation of red and green lights in the repair process of third-degree skin burns

The aim of this study was to evaluate the photobiomodulation of red and green lights in the repair process of third-degree skin burns in rats through clinicopathological and immunohistochemical parameters. Sixty male Wistar rats were divided into three groups: control (CTRL) (n = 20), red LED (RED) (n = 20), and green LED (GREEN) (n = 20), with subgroups (n = 5) for each time of euthanasia (7, 14, 21, and 28 days). Daily applications in RED (λ630 ± 10 nm, 300 mW) and GREEN groups (λ520 ± 30 nm, 180 mW) were performed at four points of the wound (total 36 J/cm² in RED and 240 J/cm² in GREEN). After euthanasia, the wound retraction index (WRI) was evaluated. In histological sections, the re-epithelialization degree, the angiogenic index (AI), and the amount of myofibroblasts in wounds were analyzed. At 14 and 21 days, the RED group induced higher re-epithelialization and WRI compared to CTRL (p > 0.05) and GREEN groups (p < 0.05). At 7 and 14 days, greater AI were observed in the GREEN group, with significant difference in relation to CTRL group at 7 days (p < 0.05). At 21 and 28 days, a trend was observed for greater amount of myofibroblasts in the GREEN group, with significant difference in relation to CTRL group at 21 days (p < 0.05). The results suggest greater potential of the green light to stimulate angiogenesis in the initial periods and myofibroblastic differentiation in the final periods of the repair of third-degree skin burns. Red light may stimulate further re-epithelialization and wound retraction, especially in advanced repair phases.