Extracellular Vesicles of Commensal Skin Microbiota Alleviate Cutaneous Inflammation in Atopic Dermatitis Mouse Model by Re-Establishing Skin Homeostasis.

Atopic dermatitis (AD) is a chronic inflammatory cutaneous disorder in which the skin is affected by microbial dysbiosis. The role of commensal skin microbiota in AD is of great interest. Extracellular vesicles (EVs) are important regulators of skin homeostasis and pathology. The mechanism of preventing AD pathogenesis through commensal skin microbiota-derived EVs remains poorly understood. In this study, we investigated the role of commensal skin bacterium Staphylococcus epidermidis-derived EVs (SE-EVs). We showed that SE-EVs significantly decreased the expression of proinflammatory genes (TNFα, IL1β, IL6, IL8, and iNOS) through lipoteichoic acid and increased the proliferation and migration of calcipotriene (MC903)-treated HaCaT keratinocytes. Furthermore, SE-EVs increased the expression of human β-defensins 2 and 3 in MC903-treated HaCaT cells through toll-like receptor 2, enhancing resistance to S. aureus growth. In addition, topical SE-EV application remarkably attenuated inflammatory cell infiltration (CD4⁺ T cells and Gr1⁺ cells), T helper 2 cytokine gene expression (Il4, Il13, and Tlsp), and IgE levels in MC903-induced AD-like dermatitis mice. Intriguingly, SE-EVs induced IL-17A⁺ CD8⁺ T-cell accumulation in the epidermis, which may represent heterologous protection. Taken together, our findings showed that SE-EVs reduced AD-like skin inflammation in mice and may potentially be a bioactive nanocarrier for the treatment of AD.