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Why do hair grow on arms and legs - but not on the palms and soles of the feet
Why do people have hair on their arms and legs, but not on the palms and soles of their feet? Researchers from the United States have taken a significant step further in answering this question. The new findings could help improve hair loss treatment.
Men are affected more frequently than women
It's normal for hair to fall out. According to experts, humans lose up to 100 hairs every day. If these do not grow again, one speaks of permanent hair loss. The most common forms include circular hair loss (alopecia areata). Men are affected more frequently than women. It is usually difficult or impossible for those affected to stop hair loss. Scientists are therefore constantly on the lookout for new therapies to help with hair loss. Researchers from the United States have now gained new knowledge.
Basic question of human evolution
Why do people have hair on their arms and legs, but not on the palms and soles of their feet?
Researchers at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia have said they have found new clues to answering this fundamental question of human evolution.
Their results, published in the specialist magazine "Cell Reports", show the presence of a naturally occurring inhibitor that plays a role in the development of hairless skin.
This blocks a signal path known as the Wnt path that controls hair growth.
Tests on mice
“We know that Wnt signals are crucial for the development of hair follicles. Blocking causes hairless skin and turning it on causes more hair formation, ”study author Sarah El Millar said in a message.
"In this study, we showed that skin in hairless regions naturally produces an inhibitor that prevents Wnt from doing its job."
This inhibitor is a protein called Dickkopf 2 (DKK2). This occurs in certain embryonic and adult tissues, where it plays different roles.
Researchers tested plantar skin from mice - roughly the equivalent of the underside of the human wrist - and found that DKK2 was found in high concentrations.
When the protein was genetically removed, the hair began to grow in this normally hairless area of the skin.
"This is important because Wnt is still present in hairless regions. It is only blocked, ”says the study author.
Some mammals develop hair on their plantar skin
Some mammals like rabbits and polar bears have hair on their plantar skin. The Millar research group found that, unlike mice, DKK2 is hardly active in these animals. This explains why hair can develop there.
Research suggests that DKK2 production in certain skin regions has been altered during evolution to create different patterns of hairless or hairy skin depending on the animal's needs.
Possible therapeutic approach against hair loss
Hair follicles develop in fetal life, but their production stops after birth. As a result, hair follicles do not grow back after severe burns or deep wounds in the skin.
According to the American Academy of Dermatology, more than 80 million people in America have androgenetic alopecia, which is also known as baldness.
Genome-wide association studies have identified DKK2 as a potential candidate gene associated with this disease, suggesting a potential therapeutic target.
"We hope that our research will reveal new ways to improve wound healing and hair growth, and we intend to continue pursuing these goals," said Millar. (ad)