How does your skin smell? Pretty well, as it turns out, thanks to receptors dotted all over you. What's more, they could help you heal.
There are more than 350 types of olfactory receptors in the nose, tuned to different scents. About 150 are also found in internal tissues such as those of the heart, liver and gut, but they are hard to study.
Hanns Hatt's lab at Ruhr University Bochum in Germany focused on skin, which is easier to study, and tested the response to scents of receptors in keratinocytes, the main skin cell type.
They found that Sandalore – a synthetic sandalwood oil used in aromatherapy, perfumes and skin care products – bound to an olfactory receptor in skin called OR2AT4. Rather than sending a message to the brain, as nose receptors do, the receptor triggered cells to divide and migrate, important processes in repairing damaged skin.
Healing boost
Cell proliferation increased by 32 per cent and cell migration by nearly half when keratinocytes in a test tube and in culture were mixed for five days with Sandalore. Natural sandalwood oil and 10 different synthetic versions were tested, but only three had a beneficial effect.
"There is a big trend towards odour receptors being found elsewhere in the body doing other jobs," says Joel Mainland of the Monell Chemical Senses Center in Philadelphia. So it is not unexpected to find receptors in skin, but it is a surprise to learn that they are involved in wound healing.
The concentrations of Sandalore used were a thousand times higher than those needed to activate a receptor in the nose. So a skin cream rather than aromatherapy would probably be needed to promote a healing effect, says Mainland.
Not for everyone?
Hatt and Mainland both caution that these olfactory receptors are very finely tuned, as is demonstrated by their distinguishing between various synthetic versions of sandalwood oil. And there is genetic variability in human receptors, so your receptor might be a bit different from your neighbour's.
It leaves open the question of whether receptors might differ so much between individuals that the synthetic sandalwood that benefits one person might be neutral or even toxic to another.
Hatt says the 150-200 olfactory receptors identified in tissue outside the nose represent a new family of targets for experiments and new opportunities to treat disease.
Treatments that heal wounds and repair the effects of ageing in the skin with topical products are likely to be the easiest to develop, he says. Understanding receptors on internal organs and creating beneficial drugs is likely to take longer.
Journal reference: Journal of Investigative Dermatology, DOI: 10.1038/jid.2014.273.
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