Email; info@clinicatanaka.jp The necessity of solar near-infrared protection shown through gene expression changes Yohei Tanaka, M.D.,Ph.D. Clinica Tanaka Plastic, Reconstructive Surgery and Anti-aging Center, 390-0874, Nagano, Japan Email; info@clinicatanaka.jp Results: The cell viability was significantly decreased after 10 rounds of NIR irradiation at 20 J ⁄cm2 in NIR treated cells without a protective polycarbonate plate and NIR treated cells using the polycarbonate plate to block only UV. Assuming that the cell viability of the non-irradiated control to be 100, the cell viability of NIR treated cells without any protection was 0.2. The cell viability of the NIR treated cells with the polycarbonate plate to block only UV was 0.3, the cell viability of the NIR treated cells with the polycarbonate plate to block both UV and NIR was 85.1, as shown in Figure 2. A DNA microarray with over 62,000 different probes showed 25 and 152 genes that were up- or down-regulated by at least 4- and 2-fold, respectively, after NIR irradiation. Quantitative real-time PCR analysis revealed that 2 variants of epidermal growth factor receptor in human corneal epithelial tissue were also significantly up-regulated after 5 rounds of 10 J ⁄cm2 irradiation (p < 0.05), as shown in Figure 3. The results of gene expression changes revealed that solar NIR can induce tissue damage. Conclusion: NIR significantly decreased human fibroblast cell viability. As human skin is exposed to tremendous amounts of both solar and artificial NIR from medical devices and electrical appliances, and most UV blocking materials do not sufficiently block NIR, further protection from NIR should be widely prevalent to prevent tissue damage. Background: Over half of the solar energy reaching the Earth consists of near-infrared (NIR), and intensive or long-term solar NIR exposure induces photoaging. Despite the prevalence of a variety of ultraviolet protection, such as sunscreen, sunglasses, glasses, and films, that are useful in protecting the skin against ultraviolet exposure, solar visible light and NIR cannot be blocked and the necessity to protect against solar NIR has not been well investigated. Objectives: To investigate the necessity of solar NIR protection, I assessed cell viability of human fibroblast cells after NIR irradiation simulating solar NIR exposure using 2 sets of transparent polycarbonate plates, one to block ultraviolet and the other to block both ultraviolet and NIR. Further, DNA microarray and quantitative real-time PCR analysis was performed to assess gene expression levels in a 3-dimensional reconstructed corneal epithelial model. Materials and Methods: NIR treatment. The NIR device emits an NIR spectrum between 1000-1400 and 1500-1800 nm, that simulates solar NIR radiation that reaches the skin of humans on the Earth’s surface. Polycarbonate plate. The polycarbonate plate to block UV (Panlite L-1225Z 100, TEIJIN, Tokyo, Japan) and the polycarbonate plate to block both UV and NIR (Panlite AM-1107ZV; TEIJIN) were used in this study (see Figure 1). The thickness of each plate is 2mm. Corneal epithelial model . A 3-dimensional reconstructed human corneal epithelial model (LabCyte CORNEA-MODEL, Japan Tissue Engineering Corporation, Aichi, Japan) was used as an in vitro model of corneal tissue. Figure 2. The cell viability of human fibroblast cells after NIR treatment was evaluated by MTT assay. Figure 3. Quantitative real-time PCR validation of EGFR. Figure 1. The appearance of the polycarbonate plates to block UV (Left), to block UV and NIR (Right). This Japanese plate to block UV is exported several tons every month to make eyewear and sunglasses.