De Novo Production of Dermal Papilla Cells during the Anagen Phase of the Hair Cycle

The study investigated the generation of new dermal papilla (DP) cells in mice during the anagen phase of hair growth. Researchers created a mouse line, Cor-cre, to track DP cells using a fluorescent protein marker. They discovered that by the end of the anagen phase, almost all DP cells were labeled with yellow fluorescent protein (YFP), indicating the addition of new cells to the DP. This finding was supported by the absence of unlabeled DP cells in sectioned follicles. The results suggest that the anagen phase environment promotes the recruitment of new cells to the DP, which is relevant for understanding hair growth and loss. The study, which analyzed 129 follicles at post-natal day 13 and 256 follicles during early anagen from five mice, highlights that DP size regulation is dynamic and suggests that maintaining hair size is not due to a static DP cell population. Identifying the source of DP progenitor cells and the mechanisms controlling DP cell quantity could aid in developing better hair loss treatments.