EVALUATION OF DAILY PHOTOPROTECTION USING RECONSTRUCTED SKIN MODEL : Relevance of UVA absorption profile and SPF value
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One of the major long term consequences of chronic non extreme sun exposures is the development of photoaging. The recent definition of a standard daily ultraviolet radiation (DUVR) spectrum has ...
One of the major long term consequences of chronic non extreme sun exposures is the development of photoaging. The recent definition of a standard daily ultraviolet radiation (DUVR) spectrum has allowed us to reproduce non-zenithal sun exposure conditions. Exposure to simulated DUVR induces biological damage in human skin, suggesting the need for an appropriate daily photoprotection. The reconstructed human skin in vitro, including a living dermal equivalent and a fully differentiated epidermis represents a predictive tool to study the effects of UV. In the present study, sunscreen products were evaluated after topical application on human reconstructed skin in vitro. Two commercial sunscreens (A and B) having similar SPF value (~15) but different profile of transmission over the UVA range were tested on skin models exposed to increasing doses of DUVR. Another pair of sunscreens was also tested. Product C had a SPF ~18 with a well-balanced UVB/UVA absorption profile and product D, with SPF ~27 and low UVA absorption. Biological parameters were assessed by (i) histology, (ii) immunostaining of dermal fibroblasts and (iii) MMP-1 production. Products A and C gave a better protection from DUVR with regard to fibroblast alterations and MMP-1 release compared to products B and D respectively. These results support that a well balanced profile of absorption and the level of UVA protection is of higher relevance than the SPF value to ensure an efficient daily photoprotection from DUVR with regard to end points evaluated in this study, especially the photoaging related biological markers.
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