Near-infrared irradiation stimulates cutaneous wound repair: laboratory experiments on possible mechanisms

Background/Aims: Several physical agents such as low-energy lasers have been used in the treatment of chronic skin ulcers. This study was performed to investigate potential effects of a newly-developed, specific near-infrared light source on wound repair. Methods: Cultured human keratinocytes, endothelial cells and fibroblasts were exposed to the light, and the production of transforming growth factor (TGF)-β1 and matrix metalloproteinase (MMP)-2 was examined by enzyme immunoassay, zymography and reverse transcription polymerase chain reaction. Incisional wounds were created in ICR and db/db diabetic mice and the effect of irradiation on wound closure was followed photographically. Results: The TGF-β1 and MMP-2 content of the medium of cultured cells was significantly elevated after irradiation. The amount of MMP-2 mRNA extracted from irradiated fibroblasts was also upregulated. Negative results in thermal controls suggested that the action of the light was athermic in nature. In animal models, the rate of wound closure was significantly accelerated by repeated exposures. Conclusion: Near-infrared irradiation potentially enhances the wound healing process, presumably by its biostimulatory effects.