The battle of the bulge: re‐evaluating hair follicle stem cells in wound repair

Abstract

The hair follicle has an established role in wound re-epithelialisation, a phenomenon that has been appreciated since at least the first half of the last century. The bulge niche, one location of hair follicle epithelial stem cells has been of particular interest to researchers over recent years, with numerous studies showing its ability to directly contribute to epidermal repair. However, recent work has highlighted other progenitor regions of the hair follicle that appear to act as stem cells during epidermal repair. In addition, several studies within the last 12 months have questioned the importance of the bulge during re-epithelialisation, producing conflicting literature. Here we provide a new model to demonstrate how several important differences in experimental design between studies could account for these seemingly opposing findings, which may have implications for how future studies are conducted. K E Y W O R D Sbulge, hair follicle, re-epithelialisation, stem cell, wound healing

Divergent proliferation patterns of distinct human hair follicle epithelial progenitor niches in situ and their differential responsiveness to prostaglandin D2

“…Basic in situ characterisation of cell cycle behaviour, including via additional parameters i.e. cell cycle-regulatory proteins 31 , 53 , is also of interest in other contexts such as stem cells in the wound response 54 , cancer 55 and in the study of hair pathology, e.g. lichen planopilaris 35 .…”

Long non‑coding RNA HOTAIR promotes burn wound healing by regulating epidermal stem cells

“…ESCs are the ‘seed cells’ in skin tissue engineering and are key functional cells during wound repair ( 55 – 57 ). ESCs are located in the basal layer of the epidermis, the outer root sheath of hair follicles and the base of sebaceous glands ( 50 ).…”

Epidermal Stem Cells in Hair Follicle Cycling and Skin Regeneration: A View From the Perspective of Inflammation

“…The implication of bulge HFSCs in re-epithelization has been established for a long time. However, different strategies for HFSCs labeling and a variety of markers employed led to a conclusion about different inputs of HFSCs subpopulations into the process (Garcin and Ansell, 2017). Some HF cells have been shown to play a dual role.…”