Hair follicle and interfollicular epidermal stem cells make varying contributions to wound regeneration

Upon wounding, multiple stem cell populations in the hair follicle (HF) and interfollicular epidermis (IFE) converge at the site of injury. Although these cells can contribute permanently to the regenerating epithelium, it remains unclear whether these contributions vary among cells originating from diverse compartments in the skin. By comparing the fates of several keratinocyte lineages, we observed here an initial decrease in both HF- and IFE-derived cells within the transient acanthotic layers of the regenerating epithelium. At the same time, the relative abundance of early-arriving IFE-derived cells specifically in the wound basal layer declined as later-arriving HF-derived cells entered the site of injury. Although laggard bulge-derived cells were typically constrained at the regenerative periphery, these cells persisted in the wound basal layer. Finally, suppressing Notch enabled IFE-derived cells to out-compete HF-derived cells. Taken together, these findings indicate that IFE-, HF- and bulge-derived cells make distinct contributions to regeneration over time. Furthermore, we speculate that extrinsic, non-genetic factors such as spatial constraint, distance from the wound, and basal versus suprabasal position may largely determine whether a cell ultimately persists.