Low Level Light Therapy Using an 830-nm Light Emitting Diode Promotes Wound Healing via TGF-β/SMAD Pathway Activation

Abstract

BACKGROUND: The transforming growth factor-β/SMAD (TGF-β/SMAD) pathway plays an important role in tissue repair and collagen synthesis. Low-level light therapy (LLLT) is increasingly used to alleviate pain and inflammation and promote wound healing. However, few studies have directly compared the effects of different wavelengths of light-emitting diodes (LEDs) or examined their individual effects at the molecular level. OBJECTIVE: Here we used a mouse model to investigate the effect of blue (410 nm), red (630 nm), and infrared (830 nm) LEDs on wound closure and assessed the underlying changes in a signal transduction pathway. METHODS: A full-thickness wound was created on the dorsal skin of mice using a 6-mm-diameter punch. In part I, the wounds were irradiated using blue, red, and infrared LEDs. In part II, the wounds were irradiated at different time points. Photo documentation, serial skin biopsies, wound measurements, and immunohistochemical staining using TGF-β/SMAD pathway-related molecules were performed. RESULTS: The overall wound closure percentage was highest during the first 10 days when an 830-nm LED was used. The wound closure process was accelerated when the irradiation was initiated immediately after wounding. Irradiation using 830-nm LED upregulated TGF-β and collagen-1 but downregulated SMAD7. CONCLUSION: Our findings show that LLLT using an 830-nm wavelength LED delivered immediately after wound formation may have the best effect on wound healing by upregulating the TGF-β/SMAD signaling pathway.