Studies on application of light emitting diodes (LED) to accelerate healing of skin wound on olive flounder, Paralichthys olivaceus

Abstract

Skin injuries of aquatic animals are common and often cause serious problems as a damaged barrier cannot maintain osmotic balance and homeostasis, leading to more vulnerable to infections. Although there have been several studies on the effects of blue & green LED light on wound healing in mammals, little is known in fish. The purposes of this study, therefore, were to determine the optimal LED conditions for fish skin wound healing and to understand cellular and molecular mechanisms of green LED light on the healing effects. In trial 1, sixty skin-wounded olive flounder in each group were exposed to ambient, white, blue, and green LED light for 28 days. In trial 2, seventy skin-wounded fish were exposed to ambient light, and 20, 40, and 60 μ·mol·m-2·s-1 of green LED light for 28 days. Five fish were sampled at 1, 3, 7, 14 and 28 days post exposure (dpe) were used to determine wound closure rate (%) and the expression of genes related to wound healing. In trial 3, skin-wounded fish in ambient, white, and green LED light groups were sampled at 3 and 7 dpe for transcriptome analysis. From trial 1 and 2, illumination of 520 nm LED at 40 μ·mol·m-2·s-1 showed the best wound healing effects on fish. In this study, fish in the green LED group showed upregulation of many genes involved in wound healing. These include genes related to growth factors and electron transport system. Also the LED condition activated JAK/STAT and MAPK signaling pathways, which transmit signals to cell division. Results obtained from this study indicate that the illumination of green LED light can accelerate wound healing, and will contribute to better understanding on phototherapy and healing mechanism in fish.