Life of the B10 Mouse: A View from the Hair Follicles and Tissue Stem Cells

The study investigated the effects of aging on skin and hair follicle characteristics in B10 mice, focusing on the stem cells for keratinocytes and melanocytes throughout the animals' lifespans. It was found that by postnatal day 200 (P200), mouse skin reaches full maturity and begins to age, affecting hair follicles (HFs). Keratin 15-positive keratinocyte stem cells are sufficiently localized in the hair bulge region by P200, contributing to hair regeneration in each growth phase. However, unusual curved hair follicles start to appear at P200 and increase with age. Similarly, melanocyte-related changes lead to a higher frequency of hypopigmented hair bulbs at P200, resulting in more white hairs over time. These curved hair follicles and white hairs are considered biomarkers of aging in mice. The study also notes a very low number of tyrosinase-related protein 2-positive melanocyte stem cells in the hair bulge, which may contribute to the aging-related characteristics in both melanocyte and keratinocyte lineages. These findings enhance the understanding of how stem cells influence hair regeneration as aging progresses.