Property characterization of reconstructed human epidermis equivalents, and performance as a skin irritation model

In recent years, in vitro skin models combining cell biology and tissue engineering have been developed in order to replace animal models for toxicological studies and to serve as research support to better understand skin biology. This study reports the development and characterization of a epidermal tissue equivalent meant to be used to develop and to evaluate the effect of applied cosmetic ingredients, and for alternative toxicological testing. This epidermis equivalent model was characterized relative to the morphological characteristics of short- and long-term maintained tissues by performing histological studies. We also studied the integrity of the epidermal barrier. Finally, with the goal of validating its use as a skin irritation test, we studied the irritation potential of 20 chemical references listed in OECD Test Guideline N°439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method). In 2015, OECD officially published the updated version of the Validated Reference Method (VRM) that uses reconstructed human epidermis models for irritation testing, thus offering the possibility for proposed putative similar test methods to obtain a validation agreement through Performance Standards-based validation. In this study, we observed that the epidermal equivalent we developed showed similarities to human in vivo skin, based on the analyzed parameters. Moreover, its performances as a skin irritation test were similar to the ones described in the OECD Test Guideline N°439.