Abstract: Ji Jie, Ding Huilin, Wang Xiaoxin, Zhang Linglin, Wang Hongwei, Wang Peiru, Wang Xiuli *. *Shanghai Skin Disease Hospital, Shanghai 200050, China Corresponding author: Wang Xiuli, Email: xlwang2001@aliyun.com 【Abstract】 Objective To evaluate the efficacy of light-emitting diode （LED） irradiation at 530 nm, 630 nm and 850 nm in the treatment of photoaged skin. Methods A total of 14 adults with photoaged extensor forearm were recruited in this study. Three areas were selected at the extensor forearm in each of these subjects and received LED irradiation at 530 nm, 630 nm and 850 nm, respectively, thrice a week for 12 sessions. Dermoscopy was used to visualize these areas before and after the irradiation, the Corneometer CM 825 to measure stratum corneum （SC） hydration, Tewameter TM 300 to determine transepidermal water loss （TEWL）, and CM-2600d spectrophotometer to measure L* value and melanin index （MI）. Tissue specimens were obtained from these areas irradiated with LED at 530 nm （n = 5）, 630 nm （n = 5） and 850 nm （n = 4） separately before and 6 weeks after the initial irradiation, and subjected to histopathological examination. Results Both skin texture and pigmentation were improved in 10 and 7 testees after 12 sessions of LED irradiation at 630 nm and 850 nm, respectively, but the skin texture became rougher and pigmentation was increased in 7 testees after LED irradiation at 530 nm. After LED irradiation at 630 nm and 850 nm, the testees experienced an obvious increase in SC hydration （（37.9 ± 7.7） au and （34.5 ± 7.1） au at 6 weeks after the initial irradiation vs. （33.1 ± 6.1） au and （32.0 ± 7.0） au before irradiation, both P < 0.05）, but a significant decrease in TEWL value （（9.8 ± 2.5） and （10.9 ± 2.5） g?m-2?h-1 at 6 weeks after the initial irradiation vs. （14.0 ± 1.8） and （14.2 ± 2.6） g?m-2?h-1 before irradiation）, with no significant changes in L* value or MI （both P > 0.05）. No evident alteration was observed in SC hydration or TEWL value （both P > 0.05）, while the L* value significantly decreased （P < 0.05） and MI increased （P < 0.05） after LED irradiation at 530 nm. Histopathological examination showed photo-induced denaturation of collagen fibers and elastic fibers in the dermis of these subjects before irradiation, as well as nascent collagen fibers and elastic fibers in a more dense and regular arrangement after irradiation at the three wavelengths. Conclusions LED irradiation at both 630 nm and 850 nm can improve the appearance and barrier function of, and stimulate the proliferation and rearrangement of collagen fibers and elastic fibers in, photoaged skin, while LED irradiation at 530 nm increases skin pigmentation.

Key words: Skin aging, Light, Skin barrier function