Abstract: Yuan Chao, Qian Chunyan, Yang Lijie, Wang Xuemin. Skin & Cosmetic Research Department, Shanghai Skin Disease Hospital, Shanghai 200443, China Corresponding author: Wang Xuemin, Email: dermxmwang@126.com 【Abstract】 Objective To evaluate skin barrier function in patients with atopic dermatitis （AD）, and to assess its relationship with claudin-1 expression. Methods Totally, 11 patients with AD and 11 healthy human controls were recruited in this study. A Tewameter TM210 was used to measure transepidermal water loss （TEWL） value, and high-frequency ultrasound to determine epidermal thickness and density, in lesional and non-lesional skin of the patients and normal skin of the healthy controls. A double-antibody sandwich enzyme-linked immunosorbent assay （ELISA） was performed to determine the serum level of free claudin-1 in these subjects. One-way analysis of variance and t test were carried out to compare these parameters in different groups, and Pearson′s correlation analysis to estimate the relationship between different parameters. Results The TEWL value was significantly higher in lesional skin than in nonlesional skin of patients with AD and normal skin of the healthy controls （（36.9 ± 34.2） vs. （9.1 ± 6.0） and （4.4 ± 3.1） g·m-2·h-1, both P < 0.05）. The epidermal thickness in AD lesions was （0.23 ± 0.04） mm, significantly higher than that in nonlesional skin （（0.18 ± 0.03） mm, P < 0.01） and normal control skin （（0.18 ± 0.02） mm, P < 0.01）. Ultrasound images revealed a characteristic subepidermal low echo-genic band in the AD lesions. The patients with AD showed a significantly lower serum level of claudin-1 compared with the healthy controls （（0.80 ± 0.88） vs. （1.73 ± 1.85） μg/L, P < 0.05）. Moreover, the serum level of claudin-1 was negatively correlated with epidermal thickness （r = －0.61, P < 0.01）, but positively correlated with the inverse of TEWL （1/TEWL, r = 0.44, P < 0.05）. Conclusions The impaired skin barrier function, which may be evaluated by TEWL, 1/TEWL and epidermal thickness, is associated with the expression of claudin-1 in patients with AD.

Key words: Dermatitis, atopic, Skin barrier, Claudin-1, Tight junction proteins