The effect of ultraviolet-B exposure scheduling on the photodamage of hairless mouse skin

In a mouse model, we investigated whether different exposure protocol of ul traviolet-B with the same total doses could induce a different degree of ph otodamage in mouse skin, Two different exposure frequencies, three times or six times a week, were applied under the condition of weekly same cumulati ve irradiation dose equally for 10 weeks. Then the photodamage parameters s uch as skin wrinkling, histochemical dermal change and epidermal and dermal thickness were evaluated, Wrinkle grade, histological assessment hy score, and dermal thickness did not reveal any difference between the two groups. However, at irradiation week 10 epidermal thickness of the three times a w eek irradiation group was significantly thicker than that of the six times a week irradiation group. The same cumulative dose resulted in different ep idermal thickness, Our results suggested that exposure frequency or schedul ing could influence the epidermal damage by ultraviolet radiation even thou gh the cumulative dose is equal.