Background

Today's biologic quarry is the hair follicle, depicted on the left. While we all take hair for granted (perhaps the lyric "you don't know what you got till it's gone" is applicable), it is a complex structure lying within the skin. Stem cells are responsible for its growth and coloration, more about them shortly, and the milieu of hormones, as well as cell mediators, controls where hair grows along with its texture. In addition to housing a sebaceous gland, hair follicles have muscles, the arrector pili, responsible for raising your hair, as in the phrase "hair-raising scare," which is a real thing.

Hair follicles go through stages of growth (anagen), rest (telogen), loss (catagen and exogen), as well as renewal (kenogen). The bulbous area at the bottom of the follicle contains those previously mentioned stem cells. Hair follicle stem cells (HFSC) derived embryologically from the same layer as our skin produces a new hair follicle. In contrast, melanocyte stem cells (MeSC) derived from the layer that forms our nervous system, provides pigment to color the hair. During anagen, these stem cells are active; otherwise, they just hang out.

The Study

Looking at the pictures of our recent Presidents over two-terms suggests that stress is involved. But how? To find an answer, the researchers made use of black-coated mice, in a series of increasingly focused experiments.

So yes, my children's antics did turn my hair grey, a hair color I have earned, but not directly. It required the assistance of my sympathetic nervous system. And it may explain why some people under stress retain their hair color; they may well have more of the melanocyte stem cells to burn through. It also points towards the belief that our autonomic nervous system, of which the sympathetics are one component, has a role in cell differentiation and tissue maintenance. Perhaps being more chill can adds days to your life as well as less grey in your hair.

[1] I attribute my hair loss, on the other hand, to my wife.

Source: Hyperactivation of sympathetic nerves drives depletion of melanocyte stem cells Nature DOI: 10.1038/s41586-020-1935-3

Image of hair follicle courtesy ofHelix84derivative work in Wikimedia

Read the original post:
Why Does Hair Turn Grey? - American Council on Science and Health