Gut dysbiosis is Associated with the Development of Alopecia Areata

Alopecia Areata (AA) is a highly prevalent autoimmune disease leading to hair loss in affected individuals. Associations between changes in the microbiome composition and AA have been previously reported, however, an in-depth characterization of gut microbiota requirement for the development of AA is lacking. To investigate the functional relevance of gut microbiota to AA development in vivo, we depleted the microbiome in the C3H/HeJ mouse model of AA. We found that antibiotic treatment protected mice from AA induction and led to decreased numbers of CD8+ T cells and an increase in the Treg/CD8+ ratio in the gut and skin-associated lymph nodes. To establish the relevance to the human situation, we performed 16S rRNA gene sequencing and compared gut microbiome composition in stool samples between 34 AA patients and 12 healthy controls (HCs). We discovered a striking gut dysbiosis in AA patients compared with HCs, and in combination with shotgun metagenomics analysis performed in 30 cases and 20 controls, we identified members of the Lachnospiraceae and Bacteroidaceae families such as Eubacterium eligens, Bacteroides cellulosilyticus, and Bacteroides caccae to characterize the gut dysbiosis in AA. Taken together with recent reports of reversal of AA in patients following fecal microbiota transplant, these data suggest that the gut microbiome may contribute to the pathogenesis of AA and offer new important implications for the treatment of this disease.