UVB induced cell damage in the reconstituted human epidermis. (a) The reconstituted human epidermis was irradiated with 50, 80 or 120 mJ/ mJ/cm22 UVB. For irradiation, the medium was replaced with PBS beneath the culture insert, and the culture plate was irradiated without the plastic plate lid. After irradiation, PBS was replaced with fresh medium, and the epidermis was cultured for 24 h. (b) The viability of cells in the UVB-irradiated epidermis was measured using the MTT assay. Values are presented as the means ± SEM of three wells. (c) Histological changes in the UVB-irradiated epidermis. Black arrowheads indicate gaps formed by holes. Bars = 50 µm. (d) Thickness of the UVB-irradiated epidermis. Epidermal thickness was measured as the distance between the top of the membrane and the bottom of the cornified layer in three randomly selected fields from each epidermis. Values are presented as the means ± SEM of three wells. (e) Immunofluorescence staining for citrullinated proteins, filaggrin, loricrin, keratin 10, keratin 14, collagen type IV, and trichohyalin in the UVB-irradiated epidermis. The dotted line represents the bottom of the cornified layer. White arrowheads indicate trichohyalin. Bar = 50 µm. The statistical analysis was performed using one-way ANOVA followed by Tukey’s post hoc test. *P < 0.05, **P < 0.01.