A Novel In Vitro Dry Skin Model Using Minipig and Human Cadaver Skin for Evaluating Moisturizer Efficacy

Moisturizers are key components of skincare products, and reliable test methods are essential for evaluating their barrier-repairing and hydrating efficacy. However, the viscous and waxy nature of many cosmetic moisturizers limits the applicability of conventional cell-based in vitro assays. In this study, we developed a novel in vitro dry skin model using epidermal sheets from minipig and human cadaver skin—models widely accepted in skin absorption research. To simulate dry skin conditions, various stimuli were applied, including the lipid-extracting solvent tert-butyl methyl ether (MTBE; 100%), 50/50 MTBE/Acetone solution (M/A), the irritant surfactant sodium dodecyl sulfate (SDS; 1%), ultraviolet B (UVB) irradiation (30 mJ/cm²), and tape stripping. Skin barrier disruption and stratum corneum damage were evaluated by assessing epidermal lipid integrity, histological alterations, transepidermal water loss (TEWL), and FITC-dextran permeation. All treatments induced significant dry skin conditions, as evidenced by disrupted lipid architecture, histological damage, and increased TEWL and FITC-dextran flux. Among them, M/A applied for 5 min produced the most consistent and reproducible changes across parameters. This protocol also yielded comparable results in human cadaver skin, supporting its applicability for evaluating the skin barrier-protective effects of cosmetic ingredients.