075 Generation and quantification of oxidized squalene to develop an acne testing model in vitro based on skin tissue engineering

The main pathogenic factors associated with acne development are follicular hyperkeratinization, increased sebum excretion with alteration of the sebum composition, Propionibacterium acnes colonization, and inflammation. In this study, we focused on sebum composition and particularly on the study and role of squalene derivatives after oxidation. In the skin, sebocytes synthetize and secrete sebum, which is mostly composed of triglycerides, fatty acids, waxes, cholesterol and approximately 12% [JY1] of squalene. Evidence suggests that inflammation may be related both to the level of squalene oxidation and to the nature of oxidized by-products. As the first step to develop an in vitro acne testing model, we experimentally oxidized squalene under controlled conditions: ultraviolet irradiation, oxygen and controlled incubation. Our goal was to compare the nature of the generated compounds (squalene derivatives) to the ones described in the sebum acne patients. Oxidized squalene derivatives were analyzed and quantified by gaz chromatography coupled to mass spectroscopy (GC/MS) and nuclear magnetic resonance (NMR). In parallel, we developed an in vitro model to study acne, based on the application of oxidized squalene derivatives on reconstructed human epidermises (RHEs) that were maintained in culture. Following treatment, the morphology of the RHEs was studied, and specific markerssuch as inflammatory cytokines were measured. The intent of this study was to observe the effect of oxidized squalene application on RHEs in culture, and to correlate these effects with the nature of the compounds obtained after squalene oxidation. This model will be useful to evaluate in vitro the potential of ingredients and compounds to inhibit acne development.