Why Wounds in Your Mouth Heal Much Faster Than Wounds on Your Skin

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Ever bitten the inside of your mouth when eating or burned it when wolfing down a sizzling piece of food? Sure you have! Luckily, you're not left reeling from those wounds for long, because compared to the rest of your body, your mouth is an incredible healing machine!

In a new study published to the journal Science Translational Medicine, a team of scientists primarily based out of the U.S. National Institutes of Health discovered a potential reason why.

First off, the researchers demonstrated the mouth's amazing healing powers. They applied two small cuts – one to the inside of the cheek, and one to the arm – of thirty healthy, nonsmoking human subjects and followed the wounds' progress for up to fifteen days. As expected, wounds to the mouth healed much, much faster.

(C) Representative pictures and quantitation of healing time course of oral wounds and skin wounds in group 1 after a 3-mm primary biopsy and of group 2 after a 5-mm secondary biopsy. (D) Graphs show the healing rate of 3-mm wounds in group 1 and of 5-mm wounds in group 2.

As seen in the figure above, cuts to the mouth healed three to four times faster compared to cuts on the skin. After just three days, they were hardly noticeable.

The researchers did more than just watch the wounds heal – they collected and analyzed samples throughout the healing process, noticing marked differences in gene expression between the two wound types. Most noticeably, proteins like SOX2, PITX1, and PITX2, which can reprogram cells to specific developmental states, were much more prevalent in samples taken from the mouth wounds. This made the researchers wonder if these proteins could boost healing in skin wounds, so they created mice over-expressing the SOX2 protein and noticed that their skin wounds did indeed heal faster compared to those of normal mice, but the difference was fairly small.

With these results in hand, the researchers made some bold claims.

"Our findings could have widespread implications for the wound healing field," they wrote. "Pathways and molecules characterized in this study may facilitate rapid, scarless healing and could be considered for therapeutic application to non-oral mucosal sites."

That is a worthwhile vision, but it's probably a ways away from being realized. Healing in the SOX2 mice did not come close to the mouth's incredible rate of healing, which makes sense. The mouth is a unique, complex environment, home to all sorts of microorganisms and receptor to many things both edible and inedible. Its regenerative powers surely don't come down to a single protein.

Overall, this is a smart, elucidating study with findings that are both fascinating and functional.

Source: R. Iglesias-Bartolome, A. Uchiyama, A. A. Molinolo, L. Abusleme, S. R. Brooks, J. L. Callejas-Valera, D. Edwards, C. Doci, M.-L. Asselin-Labat, M. W. Onaitis, N. M. Moutsopoulos, J. Silvio Gutkind, M. I. Morasso, Transcriptional signature primes human oral mucosa for rapid wound healing. Sci. Transl. Med. 10, eaap8798 (2018).

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