Why stress causes gray hair
It's not just age that turns us grey, stress has also long been considered a relevant factor. But why does lack of sleep, too much work, loneliness or other mental worries rob our hair of its color? A team led by stem cell researcher Ya-Chieh Hsu from Harvard University now believes they have found the solution to the riddle – at least in mice.
The researchers stressed animals with black fur in various ways - for example by separating them from their own kind or leaving the lights on at night. In the end, all rodents had more white spots on their fur than a control group that was not stressed. Noradrenaline is the decisive factor, as the following experiment suggested: If the scientists injected the neurotransmitter under the skin of the mice, the animals' fur turned white in precisely these areas, even if they had not been exposed to any particular stress.
The researchers suspect that the so-called melanocytes play a key role here. These cells are located in the hair roots and release color pigments to the constantly growing hair. After a hair falls out, new melanocytes can form from the stem cells and enter the next cycle. Over the course of our lives, the number of stem cells decreases. The result: sooner or later we will turn gray. But since the cells have binding sites for norepinephrine, stress can also influence this process: the neurotransmitter is released in stressful situations and causes the stem cells in the hair roots to divide excessively. As a result, they migrate under the skin, which means that no pigment-forming cells remain in the hair roots. When the researchers modified the receptor in such a way that noradrenaline could no longer dock, the genetically manipulated mice remained black despite the stress.
Hsu and her team now want to investigate whether the findings might be suitable for developing a therapy against gray hair - and thus counteracting the visible consequences of stress.
