518 Development and characterization of a 3D in vitro model mimicking acneic skin

Acne is one of the main reason for dermatological consultation since it affects 80% of teenagers and 25% of adults worldwide. It is an inflammatory skin disease of the pilosebaceous unit, involving four essential factors: hyperseborrhea combined to a modification of sebum composition, colonization by Cutibacterium (formerly Propionibacterium) acnes, hyperkeratinization and secreted inflammation. Mimicking these compromised skins is a pre-requisite before the development of dedicated therapeutic molecules. Hence, the aim of this study was to develop a new in vitro 3D model mimicking acneic skin, by combining the two main factors involved in the physiopathology: sebum alteration and C. acnes invasion. To do so, normal human keratinocytes were used to generate reconstructed epidermis (RE). During emersion step, RE were either untreated and used as control or treated with: 5.104 CFU of C. acnes (CA), in order to mimic the colonization by this opportunistic microorganism: CA RE; peroxidized squalene (PS) in topic during 1 day, in order to mimic the altered sebum composition: PS RE; a combination of C. acnes and peroxidized squalene, in order to mimic acneic skin in a more physiological way: CA-PS RE. For each condition, epidermal characteristics were checked at day 11 (D11) and 14 (D14). As expected, CA-PS RE harbors an increased cytokeratin-5 staining from D11, thus revealing early hyper-keratinization of the model. As evidence of inflammation, supernatant presents higher level of IL8 than CA RE and PS RE. Regarding antimicrobial defenses, expression of specific markers was increased. On the contrary, barrier function was altered, as visualized by lucifer yellow penetration and claudin-1 staining. In conclusion, by combining two main factors involved in the physiopathology of acne, we succeeded to design an in vitro 3D model with hyper-keratinization, secreted inflammation, increased antimicrobial defenses and altered barrier function, as observed in acneic skin. This relevant model is thus suitable for the substantiation of therapeutic molecules dedicated to acne treatment.