Abstract
Hairless mice were irradiated with medium wavelength ultraviolet light (UV-B) to investigate the condition needed to prepare a solar keratosis model that would be suitable for drug efficacy studies. Female hairless mice were exposed to 0.24J/cm2 of UV-B (wavelength, 280-360nm; peak wavelength, 306nm) 3 times per week for 8, 12, or 16 weeks followed by a 4-or 8-week observation period. Tumor formation was evident in all irradiation groups. The incidence increased with irradiation period and observation period following irradiation. Histopathologically, most animals exhibited solar keratosislike lesions corresponding to intraepidermal squamous cell carcinoma or proliferation of atypical keratinocytes in the lower epidermis. Proliferation of atypical keratinocytes was also evident in the skin region where gross lesions were not evident. Based on the histopathological results, the incidence of solar keratosis increased with the duration of UV-B exposure. More than 50% of the mice in the 16-week irradiation group developed solar keratosis during the 4-or 8-week observation period following 0.24J/cm2 of UV-B irradiation. [Skin Cancer (Japan) 2006; 21: 226-231]
