A group of researchers from Harvard University have been studying the biological mechanism by which chronic stress affects the function of the hair follicle stem cells, confirming the long standing observation that stress might lead to hair loss.
They did a mouse model study in which they induced stress with the stress hormone corticosterone which is derived from the adrenal gland and is the rodent equivalent of cortisol in humans and how it regulates the hair follicle stem cell quiescence and growth.
Under chronic stress the increased levels of corticosterone prolong the quiescence (not active) and maintain the hair follicles in an extended resting phase. In contrast, when the corticosterone is absent the hair follicle stem cells enter in more regenerative cycles throughout life.
During the resting state of the hair follicle cycle, the hairs shed more easily. Hence the importance of knowing the mechanism by which we could target this pathway and increase the time the cell is in the growth phase.
The results of the study suggest that elevated stress hormones have a negative effect on hair follicle stem cells.
It was discovered that the stress hormone acts on a cluster of dermal cells underneath the hair follicle, known as the dermal papilla. This area is known to be critical for activating hair follicle stem cells. The stress hormone prevented the dermal papilla cells from secreting Gas6, a molecule that can activate the hair follicle stem cells according to the study.
Adding this Gas6 was sufficient to activate the hair follicle stem cells to promote hair growth. This pathway could be a potential area to be studied for its potential in activated stem cells and promoting hair growth.
The researchers also discovered how stress affects the melanocyte stem cells that regenerate hair pigment and how it activates the sympathetic nervous system leading to hair graying.
The discovery of how this Gas6 pathway can activate the hair follicle stem cells and promote hair growth is a first step in further understanding the pathogenesis of hair loss and how we can target stem cells in different ways, not only for hair growth but for other important clinical applications.
Choi, S., Zhang, B., Ma, S. et al. Corticosterone inhibits GAS6 to govern hair follicle stem-cell quiescence. Nature 592, 428–432 (2021).
Source link: https://www.nature.com/articles/s41586-021-03417-2