They say that Marie Antoinette's hair turned white the night
before she lost her head to the guillotine. But can stress
really have such a dramatic effect on hair color? A new study
in mice concludes that it can and credits overactive nerves
with stripping the color from the animals' locks-and possibly ours.
Researchers at Harvard's Stem Cell Institute were interested
in the stress and hair color issue. So they decided to take a
closer look at those stem cells that give rise to melanocytes-the
cells that pump pigments into each hair follicle. The stem cells
were an obvious target...
"Because changes in the stem cell population translate to changes
in hair color, which are very visible and easy to identify."
Ya-Chieh Hsu, the study's senior author.
To start, she and her colleagues subjected mice to some rodent-sized
stressors-like having their cage tilted, their bedding dampened or
their lights left on all night.
"So what did we find? We found that stress indeed leads to premature
hair graying in mice. But it took a long time for us to actually
narrow down how it occurs."
First, they thought it could be the immune system attacking the
melanocyte stem cell population.
"However, mice lacking immune cells still show premature hair graying
under stress."
Then they thought the key factor could be cortisol, the quintessential
stress hormone.
"But when we removed the adrenal glands from the mice so they cannot
produce cortisol-like hormones, their hair still turned gray under
stress."
That's when they turned their attention to the sympathetic nervous
system, which orchestrates the body's overall reaction to stress,
including the classic fight-or-flight response. Those nerves reach
out to our muscles, organs and, yes, even our hair.
"The nerve terminals wrap around each hair follicle like a ribbon."
And when Hsu and her team cut those connections, the stem cells were
spared, and the animals kept their shiny black coat even in the face
of minor discomfort. The findings appear in the journal Nature. [Bing
Zhang et al., Hyperactivation of sympathetic nerves drives depletion
of melanocyte stemcells]
It's unclear whether the same sympathetic nerves make us gray as we age.
But the results provide hope that we may someday be able to fight to
hold onto our natural hair color-and avoid that monthly flight to the
hairdresser.