Wednesday June 12 2013
Most cases of grey hair are down to genetics and age, not stress
“If you’re worried about going grey – try to relax”, the Daily Mail advises its readers, adding, “scientists have found that too much stress really does turn our hair white”.
However, the claim is simply not true.
The research this story is based on actually involved mice and human scalp cells in a lab. It looked at a group of cells known as melanocyte stem cells (McSCs) – a type of stem cell that produces melanin, a pigment responsible for skin and hair colour.
Stem cells can develop into many different cell types in the body and play a crucial role in maintenance and repair. The researchers wanted to see how McSCs reacted to three types of intervention; injury, exposure to ultraviolet B (UVB) radiation, and stress hormones.
Using both mice and samples of human tissue, the researchers found that a combination of injuries caused some of the McSCs to ‘migrate’ out of hair follicles and into the affected area of tissue.
However, it was also found that stress hormones only increased the ‘migration’ of melanocytes in the skin when the skin was damaged – in this case by exposure to UVB.
When only the stress hormones were present, no skin melanocyte stem cells were produced.
This is an interesting study, but going grey may involve many factors – including the genes we inherit. The theory that stress is a cause has yet to be proved.
One practical application of the research is that it could lead to the development of treatments which manipulate the behaviour of McSCs, which could be used for skin pigmentation disorders such as vitiligo (pale white patches on the skin, caused by lack of melanin) and piebaldism (a condition in which white patches develop on the skin).
Where did the story come from?
The study was carried out by researchers from New York University School of Medicine and Baylor College of Medicine, US. The study had no external funding, but two of the researchers are supported by, or have grants from, a number of public institutions.
The study was published in the peer-reviewed journal Nature Medicine.
Not surprisingly, the study was covered widely in the press, where it was reported with a spin promising ways to avoid going grey. The press coverage focussed on the possibility (presented as fact) that stress hormones have the potential to turn hair grey. However, there is some distance between experiments on mice and human skin cultures and the development of treatments against grey hair.
What kind of research was this?
This was laboratory research using mice and mouse and human skin cultures. Its aim was to look at the behaviour of melanocyte stem cells (McSCs) and whether these can migrate from the hair follicles to the skin.
What did the research involve?
Researchers carried out several studies. These included the following:
- Experiments on mice. Mice are different from humans in that the melanocytes in the skin disappear shortly after birth but remain in the hair follicle (presumably because mice have a coat and therefore don’t need them in their skin). The researchers used genetically modified mice with markers allowing them to track the movement of certain cells. The researchers created a small 1cm2 cut on the back of mice or exposed an area of skin to UVB and looked at whether melanocytes and melanocyte stem cells moved from the hair follicle to the skin, and what happens after that.
- Experiments on human scalp cultures to look at whether the same process happens in human skin. In this experiment, they removed melanocyte cells in the skin and analysed whether melanocytes in the follicles migrated to the skin.
- They looked at the role of Mc1r, a stress hormone receptor, in the migration of McSCs from hair follicles to skin – hormone receptors are proteins on the surface of cells that react to the effects of certain hormones. To do this they used genetically modified mice and cultured mouse cells.
What were the basic results?
Researchers found that in mice that had been cut or exposed to UVB, melanocyte stem cells moved from the hair follicle to the skin, where they produced melanocytes.
Normally, stem cells renew themselves as well as producing cells that go on to form new tissue. However, the researchers found that the stem cells moved without replicating, meaning that after damage there were fewer melanocyte stem cells in the hair follicles surrounding the wound.
After a cut, some hair follicles surrounding the wound had no melanocyte stem cells, causing the hairs growing out of that follicle to be white.
After UVB exposure, there were still enough stem cells for the hair to be coloured. The fact that stem cells move suggests that recovery from injury takes precedence over stem cell maintenance.
New hair follicles that developed in patches of repaired skin were coloured if they developed in areas of skin that had melanocytes. This suggests that the melanocyte stem cells that had migrated to the skin could revert back to follicular stem cells.
A similar process occurred in samples from human scalp (once skin melanocytes were removed, they could be replaced by melanocytes originating from the hair follicle).
The researchers then tried to determine how the stem cells were moving. They saw that a receptor on the surface of melanocytes (Mc1r) plays a role – this receptor responds to stress hormones. Fewer stem cells moved in mice that lacked this receptor.
The researchers then did an experiment where they cultured mouse skin in the presence of a stress hormone. The stress hormones increased the production of melanocytes in the skin but only when the skin was damaged – in this case by exposure to UVB.
When only the stress hormone was present, no skin melanocyte stem cells were produced.
How did the researchers interpret the results?
The researchers say that stem cell differentiation due to injury takes precedence over stem cell maintenance. The melanocyte stem cell mechanism could be manipulated they say, to develop therapies for skin pigmentation disorders. They speculate the mechanism could also explain why stress may cause both skin pigmentation and paradoxically, hair greying.
This is an interesting study and its results may eventually lead to the development of treatments for skin pigmentation disorders. Stress hormones also seem to be involved in the movement of melanocyte stem cells from hair follicles to the skin but the relationship appears complicated, involving multiple factors. Whether stress by itself causes hair to go grey is still uncertain.
Still, there is evidence that prolonged stress can damage both your mental and physical health. Visit the NHS Choices Moodzone for more information on stress and methods you can use to relieve or reduce your stress levels.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.