Revealed: why humans do not have hairy palms

We can finally understand why humans do not have hair on the underside of the hands and feet.

In an article published in the journal Cell reports, researchers at the University of Pennsylvania in the United States said they discovered a natural inhibitor secreted in hairless developing skin that blocks what geneticists call the Wnt pathway, which controls hair growth.

("Wnt" is the abbreviation of "wingless / integrated".)

"We know that Wnt signaling is essential for the development of hair follicles. blocking it causes hairless skin and its activation causes the formation of more hair, "says dermatologist and one of the authors of the study, Sarah Millar.

"In this study, we showed that skin in hairless regions naturally produces an inhibitor that prevents the TNO from doing its job."

This inhibitor is Dickkopf 2 (DKK2), a protein found in specific embryonic and adult tissues, where it plays a variety of roles.

Millar and his colleagues tested the plantar skin on the sole of the foot in mice and found that DKK2 was highly expressed. When they genetically removed it, the hair began to grow in a normally hairless region.

DKK2 is not expressed at high levels in the plantar skin of rabbit, which is why the hair can develop there. Millar says the findings suggest that the production of DKK2 in specific skin areas has been altered during evolution to allow the formation of different hairless or hairless skin patterns depending on the needs of the skin. ;animal.

The important point is that it seems that Wnt is still present in the hairless regions, but it is blocked.

Hair follicles develop during the fetal life, but their production ceases after birth. As a result, the hair follicles do not grow back after severe or deep burns. Millar and his team are currently studying whether secreted Wnt inhibitors inhibit the development of the hair follicle in these scenarios, as well as other episodes of hair loss.