Hair Follicle Stem Cells and the Collapse of Self-Tolerance in Alopecia: The Interplay of Barrier Function, the Microbiome, and Immunity

The study by Strobl et al. investigates the breakdown of immune privilege in hair follicle stem cells linked to alopecia, using a mouse model with hair follicle-specific deletion of the epidermal growth factor receptor (EGFR). This model shows chronic folliculitis, disrupted skin barrier, dysregulated microbiome, and increased JAK1/2 and STAT1 signaling, resulting in hair loss. Four interventions were identified to prevent hair loss: antibiotic treatment, genetic inhibition of JAK-STAT signaling, pharmacological JAK inhibitor treatment, and restoration of EGFR signaling. The study suggests that barrier dysfunction, dysbiosis, and inflammation contribute to chronic folliculitis and eventual permanent hair follicle destruction. JAK inhibitors may reverse hair loss in early stages, but prolonged inflammation could lead to irreversible alopecia. Further research is needed to understand the specific microbial and immune factors involved in scarring alopecia.