Cécile Bize , Virginie Anchartechahar , Alain Moga , Maxime Fontanié 
2019, 25th IFSCC conference
Human skin is naturally covered with a population of microorganisms, specialized or opportunists, so called skin microbiota. Among the multiple commensal microorganisms present in the healthy skin flora, Cutibacterium acnes (previously named Propionibacterium acnes) is a ubiquitous gram-positive aerotolerant anaerobic bacterium belonging to the Actinobacteria phylum, that predominantly resides deep within the sebaceous follicle in contact with keratinocytes. Specific metabolic features allow C. acnes to colonise the hostile lipid-rich sebaceous follicle environment. In particular, it can degrade triglycerides present in sebum to generate short-chain fatty acids that can irritate the follicular wall and induce inflammation which subsequently leads to cutaneous infections (Dréno et al., 2018). The most well-known skin ailment associated with C. acnes is acne vulgaris.
Furthermore, the severity of acne might not only be due to a specific C. acnes strain but also to host and environmental factors. C acnes infection induces keratinocytes activation and stimulates production of proinflammatory cytokines such as interleukins (IL-8, IL-1β and IL-12) and tumour necrosis factor-α (TNF-α). The major factors contributing to acne are the hypercornification of the outer root sheath and the pilosebaceous duct, increased sebum production and, potentially, the overgrowth of C. acnes and biofilm formation (Brandwein et al., 2016; Dréno et al., 2018). In this context, our aim is to investigate the effects of C. acnes secretome on a model of reconstituted epidermis (RHE). Then, we evaluate if a botanical extract from Madagascar (HMA) could reverse these deleterious effects. C. acnes (ATCC 6919) has been cultivated with squalene which is one of the major components of sebum. The resulting secretome, which is composed of the culture medium and all metabolites secreted by C. acnes, has been topically applied on RHE during 24h.
The topical application of the secretome did not induce significant change in RHE morphology (HES staining). However, C. acnes secretome affected cell viability (MTT) by -21% (p<0.001). This secretome also induced a significant increase in TEWL (trans-epidermal water loss) and tissue permeability (studied by Lucifer Yellow) by 22% and 67% respectively. pH also increased by 0.3. Moreover, this secretome induced a significant decrease of NMFs (Natural Moisturizing Factors) and ceramides contents by 21% and 33% respectively. All these data suggest that C. acnes secretome exerts deleterious effects on skin barrier function.
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