Cells and transfection.

Human immortalized keratinocytes (NHEK/SVTERT3-5) were purchased from Evercyte (Vienna, Austria). Cells were cultured in CnT-Prime epithelial culture medium (CELLnTEC, Bern, Switzerland) in dishes coated with 0.3% collagen (Nitta Gelatin, Osaka, Japan) at 37°C in the presence of 5% CO₂. Transfection was performed using ViaFect transfection reagent (Promega, Madison, WI), according to the manufacturer’s manual. For differentiation, cells were grown in 12-well dishes to almost 100% confluence, and then the medium was replaced with CnT-Prime epithelial 3D barrier medium (CnT-3D; CELLnTEC) supplemented with linoleic acid (10 μM). The cells were cultured for 14 days, with the medium refreshed every 3 days.