Project description:The resident skin microbiota plays a fundamental role in the control of skin physiology and growing evidence support the idea that, at this barrier site, both immunity and inflammatory processes are controlled by skin resident microbiota. However, how defined skin microbes influence the skin immune system under both steady state conditions and inflammatory settings remains poorly understood. Obesity has been linked to increased prevalence of skin inflammatory disorders. We used microarray analysis to investigate how Corynebacterium spp., dominant members of the skin microbiota of mice and humans, influence gene expression in the skin in mice under normal diet or a high-fat diet regimen.
Project description:Scratching damages upper layers of the skin, breaks this first line of immune defence, and leads to inflammation response, which often also modifies the microbiota of the skin. Although the healing of incision wounds is well-described, there are fewer studies on superficial wounds. We used a simulated model of skin scratching to study changes in the host transcriptome, skin microbiota, and their relationship. Additionally, we examined the effect of nanosized ZnO, TiO2, and Ag on both intact and damaged skin. At 24 h after exposure, the number of neutrophils was increased, 396 genes were differentially expressed, and microbiota compositions changed between scratched and intact control skin. At 7 d, the skin was still colonised by gut-associated microbes, including Lachnospiraceae, present in the cage environment, while the transcriptomic responses decreased. To sum up, the nanomaterial exposures reduced the relative abundance of cutaneous microbes on healthy skin, but the effect of scratching was more significant for the transcriptome than the nanomaterial exposure both at 24 h and 7 d. We conclude that superficial skin scratching induces inflammatory cell accumulation and changes in gene expression especially at 24 h, while the changes in the microbiota last at least 7 days.
Project description:Under steady state conditions, the immune system is poised to sense and respond to the microbiota. As such, immunity to the microbiota, including T cell responses, is expected to precede any inflammatory trigger. How this pool of preformed microbiota-specific T cells contributes to tissue pathologies remains unclear. Here, using an experimental model of psoriasis, we show that recall responses to commensal skin fungi can significantly aggravate tissue inflammation. Enhanced pathology caused by fungi pre-exposure depends on Th17 responses and neutrophil extracellular traps and recapitulates features of the transcriptional landscape of human lesional psoriatic skin. Together, our results propose that recall responses directed to skin fungi can directly promote skin inflammation and that exploration of tissue inflammation should be assessed in the context of recall responses to the microbiota.
Project description:Essential to terrestrial life is the formation of a competent skin barrier that prevents desiccation and entry by harmful substances. A tightly orchestrated series of cellular changes is required for the proper formation of the epidermal permeability barrier. These changes occur in the context of the commensal skin microbiota. Using germ free mice and antibiotic depletion models, we demonstrate the microbiota is necessary for proper differentiation and repair of the barrier. These effects were mediated by keratinocyte signaling through the aryl hydrocarbon receptor (AHR), a xenobiotic receptor that also regulates epidermal differentiation. Murine skin lacking keratinocyte AHR was more susceptible to infection by S. aureus and increased pathology in a model of atopic dermatitis. Topical colonization with a defined consortium of human skin commensals restored barrier competence in germ free skin and during epicutaneous sensitization; these effects were dependent on keratinocyte AHR. We reveal a fundamental role for the commensal skin microbiota in directing skin barrier formation and repair through the AHR, with far-reaching implications for the numerous skin disorders characterized by disrupted epidermal differentiation and/or barrier competence.
Project description:Profiling the skin microbiota composition from the face of healthy women. Exploring the differences between three age groups and between dry skin and not dry.
Project description:The microbiota colonizes each barrier site and broadly controls host physiology. However, when uncontrolled, microbial colonists can also promote inflammation and induce systemic infection. The unique strategies employed at each barrier tissue to control the coexistence of the host with its microbiota remain largely elusive. Here we uncover that, within the skin, host-microbiota symbiosis depends on the remarkable ability of the skin to act as an autonomous lymphoid organ. Notably, an encounter with a new skin commensal promotes two parallel responses, both under the control of Langerhans cells. On one hand, skin commensals induce the formation of classical germinal centers within secondary lymphoid organs associated with IgG1 and IgG3 antibody responses. On the other hand, microbial colonization also leads to the development of tertiary lymphoid organs within the skin itself that can locally sustain and mature IgG2b and IgG2c responses. These phenomena are supported, at least in part, by the ability of the skin regulatory T cells to convert into T follicular helper cells that accumulate within organized tertiary lymphoid organs within the dermis. Skin autonomous production of antibodies is sufficient to control local commensal colonization as well as subsequent systemic infection with the same microbe. Collectively, these results reveal a striking compartmentalization of humoral responses to the microbiota. Further, this work uncovers a previously unappreciated function for the skin as a compartment able to develop, in the absence of inflammation, powerful and long-lived antibody responses independently of secondary lymphoid organs.
Project description:How the homeostatic dialogue between the host and its microbiota is initiated remains largely unknown. Here, we show that immune response to the skin microbiota is dependent on activity of endogenous retroviruses. Notably, response to the microbiota promotes a discrete transcriptional induction of retroelements. As such, keratinocyte intrinsic sensing of endogenous retrovirus (ERV) derived DNA via cGAS/STING promotes the induction of commensal specific T cells including CD8+, CD4+ and MAIT cells. Consequently, inhibition of reverse transcriptase activity impairs both homeostatic immunity to the microbiota and associated tissue repair function. On the other hand, altered diet and in particular increase in dietary lipids primed the skin for aberrant ERV expression in the context of microbiota exposure leading to tissue inflammation. Together our results support the idea that the host may have coopted its endogenous virome as a means to communicate with exogenous microbiota resulting in a multikingdom dialogue that controls both tissue homeostasis and inflammation.