Why people on soles and palms have no hair

Why does hair grow on the arms and legs - but not on the palms and soles of the feet?

Why do people have hair on the arms and legs, but not on the palms and soles of the feet? Researchers from the United States have come a significant step further in answering this question. The new findings could help to improve the treatment of hair loss.

Men are affected more frequently than women

That hair fall out, is quite normal. According to experts, humans lose up to 100 hair every day. If these do not grow again, it is called permanent hair loss. Circular hair loss (alopecia areata) is one of the most common forms. Men are affected more frequently than women. For those affected it is usually difficult or impossible to stop the hair loss. Scientists are constantly looking for new therapies to help with hair loss. Researchers from the USA have now gained new insights.

People have hair on their legs and arms, but not on the soles of their feet and palms. American researchers have now gained new insights into why this is so. (Image: ARochau / fotolia.com)

Basic question of human evolution

Why do people have hair on the arms and legs, but not on the palms and soles of the feet?

Researchers at the University of Pennsylvania's Perelman School of Medicine in Philadelphia have now found new evidence to answer this fundamental question of human evolution.

Their results, published in the journal Cell Reports, indicate the presence of a naturally occurring inhibitor involved in the development of hairless skin.

This blocks a signaling pathway known as Wnt pathway 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 hairiness, "study author Sarah El Millar said in a statement.

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

This inhibitor (inhibitor) is a protein called Dickkopf 2 (DKK2). This occurs in certain embryonic and adult tissues where it plays various roles.

The researchers tested plantar skin of mice - approximately the equivalent of the underside of the human wrist - and found that DKK2 is 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, such as rabbits and polar bears, have hair on their plantar skin. The Millar research group found that DKK2 is barely active in these animals as opposed to mice. This explains why hair can develop there.

The research suggests that the production of DKK2 in certain skin regions has been altered during evolution to produce different patterns of hairless or hairy skin according to the needs of the animal.

Possible therapy for hair loss

Hair follicles develop in fetal life, but their production ceases after birth. As a result, hair follicles do not grow 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, also known as baldness.

Genome-wide association studies have identified DKK2 as a candidate gene associated with this disease, suggesting a potential therapeutic target.

"We hope our research will identify new ways to improve wound healing and hair growth, and we intend to continue to pursue these goals," Millar said. (Ad)