Evaluation of the protective effect of sunscreens on in vitro reconstructed human skin exposed to UVB or UVA irradiation

We have previously shown that skin reconstructed in vitro is a useful model to study the effects of UVB and UVA exposure. Wavelength-specific biologic al damage has been identified such as the formation of sunburn cells (SBC) and pyrimidine dimers after UVB irradiation and alterations of dermal fibro blasts after UVA exposure. These specific effects were selected to evaluate the protection afforded by two sunscreens after topical application on the skin surface. Simplified formulations having different absorption spectra but similar sun protection factors were used, One contained a classical UVB absorber, 2-ethylhexyl-p-methoxycinnamate. The other contained a broad-spe ctrum absorber called Mexoryl(R) SX, characterized by its strong absorbing potency in the UVA range, Both filters were used at 5% in a simple water/oi l vehicle. The evaluation of photoprotection on in vitro reconstructed skin revealed good efficiency for both preparations in preventing UVB-induced d amage, as shown by SBC counting and pyrimidine dimer immunostaining, By con trast, only the Mexoryl(R) SX-containing preparation was able to efficientl y prevent UVA-specific damage such as dermal fibroblast disappearance. Our data further support the fact that skin reconstructed irt vitro is a reliab le system to evaluate the photoprotection provided by different sunscreens against specific UVB and UVA biological damage.