Single-Cell Transcriptomics Reveals Lineage Trajectory of Human Scalp Hair Follicle and Informs Mechanisms of Hair Graying

This document presents a study that used single-cell RNA sequencing (scRNA-seq) to analyze human scalp hair follicles (hsHFs), both black and in early stages of graying, to create a detailed single-cell atlas. The study revealed new insights into the lineage trajectory of hsHFs, including differences from mouse hair follicles, such as the presence of an innerbulge-like compartment and the absence of a companion layer. It also identified that early graying in humans is not only due to the loss of melanocytes but also involves the depletion of matrix hair progenitors, which is not seen in hair follicle stem cells (HFSCs). This depletion is associated with the activation of the P53 pathway, and blocking this pathway pharmacologically was shown to mitigate hair graying in mice, suggesting a potential treatment strategy for hair graying in humans. The findings were validated using samples from multiple independent individuals.