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

Abstract

The cathelicidin antimicrobial peptide LL37 is a critical element in host defense following injury or infection, and its inappropriate expression promotes inflammatory skin diseases such as psoriasis and rosacea. We have shown that cathelicidin promotes inflammation by enabling binding of self-RNA to cell surface scavenger receptors, and that LL37 attaches to scavenger receptors in human psoriatic skin. To examine if this binding is commonly seen in other inflammatory skin diseases, we performed proximity ligation assays (PLA) using antibodies against LL37 and SR-B1, one of scavenger receptors. PLA on human skin demonstrated that the interaction between LL37 and SR-B1 was evident in situ in also rosacea, discoid lupus erythematosus, and chronic pyoderma compared to healthy skin. This result implies that the inflammatory activity of LL37 is mediated by a cell surface, scavenger receptor-dependent interaction in those inflammatory skin diseases, and that the blockade of this interaction is potentially targetable as novel anti-inflammatory therapy. 518Development and characterization of a 3D in vitro model mimicking acneic skin S Bordes, M Laclaverie, P Rouaud-Tinguely, L Marchand and B Closs R&D Department, SILAB, Brive, France 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 prerequisite 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: 5.10 4 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 ...