# An updated guide to hair follicle stem cell markers and changes in their expression with aging

## TL;DR

This review summarizes known markers for hair follicle stem cells and how these markers change with age, aiding in their identification and potential use in hair regeneration.

## Contribution

The paper provides an updated overview of hair follicle stem cell markers and their age-related expression changes based on recent single-cell RNA-sequencing studies.

## Key findings

- HFSC markers have been expanded through single-cell RNA-sequencing studies.
- New HFSC subsets with distinct marker expression have been identified.
- MicroRNAs serve as cycle-specific markers for HFSCs.

## Abstract

The availability of identification markers is a major expectation in the field of stem and progenitor cell biology, whether to decipher the hierarchy of these cellular compartments or to isolate these cells for use in tissue reconstruction and regeneration approaches. Epithelial hair follicle stem cells (HFSCs) constitute a well-established model of multipotent tissue stem cells. Knowledge of relevant HFSC phenotypes is crucial for their identification and manipulation for therapeutics, including hair regeneration in patients with alopecia and skin engineering after injury. In this review, we provide a detailed review of murine and human HFSC markers, drawing upon traditional studies that identify classic HFSC markers and highlighting single-cell RNA-sequencing studies that have greatly expanded our knowledge of HFSCs. Recently defined HFSC subsets with distinct marker expression, microRNAs that qualify as cycle-specific HFSC markers, and HFSC marker changes with aging are all discussed.