High‐resolution single‐cell transcriptomics reveals heterogeneity of self‐renewing hair follicle stem cells

• Published in: Experimental dermatology Vol. 30; no. 4; pp. 457 - 471
• Main Authors: Chovatiya, Gopal, Ghuwalewala, Sangeeta, Walter, Lauren D., Cosgrove, Benjamin D., Tumbar, Tudorita
• Format: Journal Article
• Language: English
• Published: Denmark Wiley Subscription Services, Inc 01.04.2021
• Subjects: Animals; Antigens, CD34; Bulge; CD34 antigen; Cell migration; Cell self-renewal; Gene set enrichment analysis; GSEA; Hair Follicle - cytology; hair follicle stem cells; Homeostasis; Male; Mice; Nutrients; ORS; Quiescence; scRNA‐seq; Sensory neurons; Skin; Skin - cytology; Skin Physiological Phenomena; Stem cell transplantation; Stem cells; Stem Cells - physiology; Transcription; Transcriptome; Transcriptomics; hair follicle stem cells; ORS; GSEA; scRNA-seq; Bulge; Quiescence
• ISSN: 0906-6705; 1600-0625
• DOI: 10.1111/exd.14262

Multipotent bulge stem cells (SCs) fuel the hair follicle (HF) cyclic growth during adult skin homeostasis, but their intrinsic molecular heterogeneity is not well understood. These hair follicle stem cells (HFSCs) engage in bouts of self‐renewal, migration and differentiation during the hair cycle. Here, we perform high‐resolution single‐cell RNA sequencing (scRNA‐seq) of HFSCs sorted as CD34+/K14‐H2BGFP+ from mouse skin at mid‐anagen, the self‐renewal stage. We dissect the transcriptomic profiles and unravel population‐specific transcriptional heterogeneity. Unsupervised clustering reveals five major HFSC populations, which distinguished by known markers associated with both the bulge and the outer root sheath (ORS) underneath. These populations include quiescent bulge, ORS cellular states and proliferative cells. Lineage trajectory analysis predicted the prospective differentiation path of these cellular states and their corresponding self‐renewing subpopulations. The bulge population itself can be further sub‐divided into distinct subpopulations that can be mapped to the upper, mid and lower bulge regions, and present a decreasing quiescence score. Gene set enrichment analysis (GSEA) revealed new markers and suggested potentially distinct functions of the ORS and bulge subpopulations. This included communications between the upper bulge subpopulation and sensory nerves and between the upper ORS and skin vasculature, as well as enrichment of a bulge subset in cell migratory functions. The lower ORS enriched genes may potentially enable nutrients passing from the surrounding fat and vasculature cells towards the proliferating hair matrix cells. Thus, we provide a comprehensive account of HFSC molecular heterogeneity during their self‐renewing stage, which enables future HF functional studies.