Defining Transcriptional Signatures of Human Hair Follicle Cell States.

The epidermis and its appendage, the hair follicle, represent an elegant developmental system in which cells are replenished with regularity because of controlled proliferation, lineage specification, and terminal differentiation. Although transcriptome data exists for human epidermal and dermal cells, the hair follicle remains poorly characterized. Through single-cell resolution profiling of the epidermis and anagen hair follicle, we characterized the anatomical, transcriptional, functional, and pathological profiles of distinct epidermal, hair follicle, and hair follicle-associated cell subpopulations including melanocytes, endothelial cells, and immune cells. We additionally traced the differentiation trajectory of interfollicular and matrix cell progenitors and explored the association of specific cell subpopulations to known molecular signatures of common skin conditions. These data simultaneously corroborate prior murine and human studies while offering new insights into epidermal and hair follicle differentiation and pathogenesis.