Reconstructed human epidermis models (RHE) constitute an innovative alternative to study
phototoxicity and photoprotection in the cosmetic industry. However, little information is currently available concerning the harmful effects of solar-simulated radiation (SSR) in these in vitro skin models. In this study, the phototoxic effects of a single acute SSR dose of 275 kJ m(-2) were evaluated in a validated RHE model (from SkinEthic), and were compared with those obtained from an ex vivo skin organ culture recently developed from domestic pig ears. The RHE model was well differentiated in vitro and released a significant level of the cytosolic
enzymes lactate dehydrogenase (LDH) and extracellular signal-related
kinase 2 (ERK2)
protein in the culture medium 24 h after SSR exposure. The SSR-induced cytotoxicity was related to the formation of
sunburn cells and the appearance of DNA damage (
thymine dimer and DNA fragmentation) in keratinocytes. Interestingly, these
DNA alterations were associated with the activation of the
caspase-3 protease, mainly in the basal layers of the epidermis. In addition, the RHE model responses were comparable with porcine skin following solar irradiation, and none of the above cellular responses was observed in non-irradiated skin models. Finally, topical application of a broad-spectrum UVB + A
sunscreen formulation efficiently protected both the RHE and pig skin against the deleterious effects of SSR. Thus, both RHE and ex vivo pig skin organ culture models are complementary tools in the assessment of SSR-induced DNA damage and apoptosis, and they may be used to evaluate the photoprotective capacity of cosmetic formulations.