Reduced humidity induces skin barrier dysfunction and secretion of dipeptidyl peptidase-4 (DPP-4) in a skin-equivalent model

Seasonal changes can affect the physiological condition of the skin and cause various cutaneous disorders. The skin barrier function tends to worsen during winter when humidity is lower compared to other seasons. To determine the influence of relative humidity (RH) on the function of the skin barrier, we performed biological and histological assays using skin equivalents that were cultured under reduced humidity in an environmental humidity chamber. We found that reduced humidity led to decreased epidermal thickness and disruption of the skin barrier. Reduced humidity induced the decrease of filaggrin, loricrin and damage to tight junction. In addition, dipeptidyl peptidase-4 (DPP4), which has roles in the immunological process, was upregulated in a skin-equivalent model under reduced humidity. These results suggest that reduced humidity affects the skin barrier function and regulates the secretion of DPP4 in a skin-equivalent model.