A research group at Tokyo Medical and Dental University found that the regeneration and aging of hair follicles, the organelles that grow hair, are determined by the type of stem cell division.
It is known that in many tissues and organs, their function declines due to the depletion of stem cells with aging.Hair follicles are one of them, and in response to age-related DNA damage and environmental stress, hair follicle stem cells produce epidermal keratinocytes instead of self-renewing or producing hair-growth cells.By eliminating these epidermal keratinocytes as dandruff and dirt, the hair follicles are gradually miniaturized, causing thinning hair and hair loss.
However, the actual state of stem cell self-renewal has not yet been clarified, and the existence of stem cell division type in this mechanism and its association with tissue regeneration and aging have not been clarified.
Therefore, the research team analyzed the genealogy and division axis of mouse hair follicle stem cells, and in young mice, hair follicle stem cells double "regenerative" stem cell division, that is, typical symmetric division and stem cell niche. We have found that "special" asymmetric division (longitudinal division) occurs in aged mice, while undergoing asymmetric division.This special stem cell division produces cells that differentiate into epidermal keratinocytes when they divide perpendicular to the basement membrane, and was similarly observed in the presence of genomic stress as well as aging.
In addition to the decreased expression of type XVII collagen in hair follicle stem cells, it was also found to be caused by the decreased expression of aPKCλ, which is also known as a molecule involved in epithelial polarity formation, and to promote the depletion of stem cells.Furthermore, decreased expression of type XVII collagen and aPKCλ was also observed in human miniaturized hair follicles, suggesting that a similar mechanism exists in human hair follicles.
This result, which elucidates a part of the stem cell division program that controls tissue regeneration and aging, is expected to lead to the development of treatment methods for alopecia and anti-aging strategies for epithelial tissues.
Paper information:[Nature aging] Distinct types of stem cell divisions determine organ regeneration and aging in hair follicles
