Commensal microbiota regulates skin barrier function and repair via signaling through the aryl hydrocarbon receptor

The epidermis forms a barrier that defends the body from desiccation and entry of harmful substances, while also sensing and integrating environmental signals. The tightly orchestrated cellular changes needed for the formation and maintenance of this epidermal barrier occur in the context of the skin microbiome. Using germ-free mice, we demonstrate the microbiota is necessary for proper differentiation and repair of the epidermal barrier. These effects are mediated by microbiota signaling through the aryl hydrocarbon receptor (AHR) in keratinocytes, a xenobiotic receptor also implicated in epidermal differentiation. Mice lacking keratinocyte AHR are more susceptible to barrier damage and infection, during steady-state and epicutaneous sensitization. Colonization with a defined consortium of human skin isolates restored barrier competence in an AHR-dependent manner. We reveal a fundamental mechanism whereby the microbiota regulates skin barrier formation and repair, which has far-reaching implications for the numerous skin disorders characterized by epidermal barrier dysfunction. [Display omitted] •Germ-free mice have abnormal skin barrier structure and function•Keratinocyte aryl hydrocarbon receptor (AHR) mediates barrier function and repair•Human skin commensal microbes activate keratinocyte AHR•Targeting the microbiota-AHR axis promotes skin barrier repair in disease models A self-renewing skin barrier is needed for terrestrial life. Uberoi et al. demonstrate that the skin microbiota regulates barrier repair and integrity by activating keratinocyte aryl hydrocarbon receptor (AHR). This microbiota-AHR axis was targeted with a defined consortium of human skin commensals to improve barrier repair in disease models.