A human skin model to evaluate the protective effect of compounds against UVA damage

Objective The main function of skin is to protect the body from external aggressions. Over time, normal skin ageing is accelerated by external stresses such as smoking, pollution, chemical products and radiation. UV light, in particular UVA, causes DNA damage, apoptosis and morphological modifications, which are responsible for both premature ageing and cancer. The aim of this study was to establish a discriminatory and sufficiently reproducible cutaneous model for evaluating UVA damage, to enable testing for effectiveness of potentially protective compounds. Methods The cutaneous model is based on Human skin explants irradiated with UVA. Deleterious effects on epidermis were observed and quantified by haematoxylin–eosin staining and by immunofluorescence of ɣ‐H2Ax, cytokeratin 5, involucrin and loricrin protein. Dermis deterioration was evaluated by transmission electronic microscopy and zymography in situ. Results We were able to observe and quantify deleterious effects associated with UVA irradiation: epidermal and dermal disruption, appearance of Sunburn cells, increased DNA damage and induced apoptosis. The use of this model in the evaluation of protective compounds was first confirmed using sunscreens, then further validated with a panel of active ingredients which showed beneficial effects on epidermis morphology and DNA integrity after UVA exposure. Conclusion We have developed a model and a standardized protocol, based on the use of human skin explants, which allows us to explore the protective effect of active ingredients to environmental stresses such as UVA. Résumé Objectifs La fonction principale de la peau est de protéger le corps des agressions externes. Au cours du temps, le vieillissement naturel de la peau est accéléré par des stress externes comme la cigarette, la pollution, les produits chimiques et les radiations solaires. Le rayonnement ultraviolet, en particulier les UVA, cause des dommages de l'ADN, l'apoptose et des modifications morphologiques qui sont responsables du vieillissement prématuré et de cancers. Le but de cette étude est d'établir un modèle cutané reproductible et discriminatoire pour évaluer les dommages créé par les UVA et tester l'efficacité de potentiels produits protecteurs. Méthodes Ce modèle cutané est basé sur un explant de peau humaine irradié aux UVA. Les effets délétères sur l'épiderme sont observés et quantifiés par coloration Hématoxyline‐éosine et par des immunofluorescence des protéines ɣ‐H2Ax, cytokérat