Background: Pruritus is a symptom in atopic dermatitis (AD). Previous studies have reported that increased intraepidermal neurites are observed in AD, suggesting that the neuritogenesis is related to itching in the skin.
Objective: This study was conducted to reveal the mechanism of intraepidermal neurite formation in AD.
Methods: In this study, we used conventional (Conv) NC/Nga mice with AD. NC/Nga mice maintained in specific pathogen-free (SPF) condition were used as a control with no AD. Distribution of intraepidermal neurites and expression patterns of growth factors (NGF and amphiregulin (AR)) and cell-cell junctional molecules (E-cadherin, zona occludens 1 (ZO-1) and desmoglein 3 (Dsg3)) were examined in the skins by immunohistochemistry or quantitative RT-PCR. Furthermore, detection of gelatinase activity was performed with in situ zymography. The same experiments were conducted in ICR mice for comparison with NC/Nga mice.
Results: Neurite density and expression levels of growth factors and gelatinase were remarkably increased in the epidermis of Conv-NC/Nga mice compared with those of SPF-NC/Nga mice. Decreased expression of E-cadherin and ZO-1 and misexpression of Dsg3 were also observed in the atopic skins. In comparison with ICR mice, increases of neurite density and gelatinase activity were found in the skins of SPF-NC/Nga mice but expression levels of growth factors and cell-cell junctional molecules were unchanged.
Conclusions: Increases of growth factors and gelatinase activity may be related to neurite outgrowth in the epidermis of atopic NC/Nga mice. Additionally, abnormal expressions of cell-cell junctional molecules in the epidermis may provide intercellular spaces for the neurite formation.