New insights into the role of Cutibacterium acnes -derived extracellular vesicles in inflammatory skin disorders

ABSTRACT Background Cutibacterium acnes ( C. acnes ) is one of the most prevalent bacteria that form the human skin microbiota and, depending on multifactorial conditions it can help to maintain the skin homeostasis. Actually, different phylotypes of C. acnes have been associated with different degrees of acne vulgaris development, while others, such as the H1 subtype, have been detected in patients with non-acneic skin. However, due to the physiology of the skin, the skin microbiota neither has direct access to the skin’s sebaceous glands nor to the main immune cells, as they are protected by a sebum layer. Therefore, the inter-kingdom communication relies on secreted factors and bacterial extracellular vesicles (EVs). In this context, the purpose of this project was to study the role of EVs secreted by three different phylotypes of C. acnes (A1 as pathogenic, H1 as beneficial and H2 as commensal). Results Main findings showed that the proteomic profile of the cargo embodied in the EVs reflects unique characteristics of the different C. acnes phylotypes in terms of lifestyle, survival and virulence. Moreover, in vitro skin models showed an extended pro-inflammatory modulation of A1 EVs, while H1 EVs displayed a high sebum-reducing potential. Conclusions This study has highlighted the role of C. acnes EVs as key modulators during skin alterations, specially H1 EVs as an alternative based-natural treatment to fight acne vulgaris symptomatology.