Our hair colour seems to have an unexpected role in wound healing
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Redheads may experience slower wound healing than their blonde, brunette or black-haired counterparts. A study in mice shows that a genetic variant that causes the hair colour seems to impede the rate at which lesions close up – a discovery that could help us better treat wounds among people with hair of all hues.
Our hair colour is heavily determined by a gene called MC1R, which encodes for a protein that controls the ratio of a black-brown pigment to a red-yellow one in hair follicles.
People with brown or black hair carry MC1R variants that encode for active forms of this protein. But nearly all red-haired people have less active or completely inactive forms due to mutations in MC1R. The genetics of hair colour is more complex among blondes, who also may have active or inactive forms of the protein.
The same protein is also in our skin, where it has anti-inflammatory effects. This led Jenna Cash at the University of Edinburgh, UK, to wonder whether it influences wound healing. This process requires a brief inflammatory response to clear out microbes and dead cells from the lesion, but if it is excessive or prolonged, the healing is impaired.
To explore this, she and her colleagues surgically created 4-millimetre-wide wounds on the backs of mice with black hair and red hair, the latter of which had a completely inactive form of the MC1R protein.
A week later, the wounds on the red-haired mice had shrunk by 73 per cent, on average, compared with 93 per cent in the black-haired group.
Off the back of this, the team wondered whether an experimental topical drug that raises the activity of active forms of the protein – but doesn’t work on completely inactive versions – could improve the healing of chronic wounds. These often occur among people with diabetes, where excess inflammation from consistently high blood sugar levels can stall wound healing.
To put it to the test, the researchers generated wounds in black-haired mice, to which they applied the drug and bandages. Other black-haired mice had the same wounds but were treated with a saline solution and bandages.
A week later, they found that the treated mice’s wounds had shrunk by 63 per cent, on average – more than double the rate of the control animals’ wounds. “If you’ve got a wound that’s half the size, I think patients would be quite thrilled about that, particularly after such a short time,” says Cash. Further analyses revealed the drug works by reducing the number of inflammatory immune cells.
As wound healing is quite similar between mice and humans, the approach holds promise for treating people, even redheads, most of whom have MC1R proteins with some activity, says Cash. However, those with completely inactive forms wouldn’t benefit, she says.
Drugs that target this protein are already used to treat conditions such as erythropoietic protoporphyria, where the skin is overly sensitive to sunlight, so the team suspects the approach will have an acceptable safety profile, says Cash. But further studies are needed to verify this, says Kath Bogie at Case Western Reserve University in Ohio. Cash says the team plans to start trials in people soon.
Further work should also test whether the drug works safely and effectively in infected wounds, says Bogie. “There’s a potential the drug could disrupt the response to infection, or it could have the opposite effect,” she says.
This may feel like bad news for some redheads, with previous research suggesting they also feel more pain. But Cash stresses they shouldn’t be concerned. “People with red hair shouldn’t worry. We don’t yet have data from humans, and if a red-haired individual sees slightly slower wound healing, they may not even notice – it’s probably quite a small effect.”
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