Hair Follicle Epithelial Stem Cells Contributing to Interfollicular Epidermis during Homeostasis

The mammalian skin is a crucial barrier, with the epidermis as its protective, renewing outer layer. Loss of epidermal function is lethal, so multiple stem cell populations likely support the interfollicular epidermis (IFE) for survival. We show that KROX20 marks a diverse stem cell population in the upper and middle mouse hair follicle (HF), partially overlapping with known HF stem cells. Lineage tracing reveals that Krox20-lineage cells migrate from the HF to the IFE, contributing to both basal and suprabasal layers. Spatial transcriptomics analysis of the skin was used to confirm this migration. Dorsal skin samples were collected from Krox20-CreERT; R26-tdTomato mice at P38 (n=3), induced at P2, with each mouse corresponding to one skin section per slice. For the three biological replicates (three mice), four technical replicates were used across the four capture areas.