Researchers discover why some parts of the body have hair and others don't

November 28, 2018, Perelman School of Medicine at the University of Pennsylvania
Strand of human hair at 200x magnification. Credit: Jan Homann/Wikipedia

Why do humans have hair on our arms and legs but not on the palms of our hands and the soles of our feet? It's a fundamental question in human evolution that researchers at the Perelman School of Medicine at the University of Pennsylvania say they've found clues to in a new study. Their findings reveal the existence of a naturally-occurring inhibitor secreted in developing hairless skin which blocks a signaling pathway, known as the WNT pathway, that controls hair growth. Cell Reports published the study today.

"We know that WNT signaling is critical for the development of follicles; blocking it causes hairless skin, and switching it on causes formation of more hair," said the study's co-senior author Sarah E. Millar, Ph.D., the Albert M. Kligman Professor in Dermatology and Director of the Penn Skin Biology and Diseases Resource-based Center. "In this study, we've shown the skin in hairless regions naturally produces an inhibitor that stops WNT from doing its job."

That natural inhibitor is Dickkopf 2 (DKK2)—a protein that is found in specific embryonic and adult tissues where it plays a variety of roles. Researchers tested plantar skin from mice—roughly the equivalent of the underside of the human wrist—and found that DKK2 was highly expressed. Furthermore, when they genetically removed DKK2, hair began to grow in this normally hairless skin region.

"This is significant because it tells us WNT is still present in hairless regions, it's just being blocked," Millar said.

Some mammals, such as rabbits and polar bears, naturally develop hair in their plantar skin. Millar's research group found that, unlike in mice, DKK2 is not expressed at high levels in rabbit plantar skin, explaining why hair can develop there. These findings suggest that production of DKK2 in specific skin regions has been altered during evolution to allow different patterns of hairless or hairy skin to form according to the needs of the animal.

Hair follicles develop during fetal life, but their production stops after birth. As a result, hair follicles fail to re-grow after severe burns or extensive, deep wounds in the skin. Millar and her team are now investigating whether secreted WNT inhibitors suppress development in these scenarios.

While some regions of the human body are naturally hairless, others become so due to a variety of diseases. According to the American Academy of Dermatology, more than 80 million people in America have androgenetic alopecia, also called male- or female-pattern baldness. Genome-wide association studies have identified DKK2 as a possible candidate gene associated with this condition, suggesting it as a potential therapeutic target.

"We hope that these lines of investigation will reveal new ways to improve wound healing and , and we plan to continue to pursue these goals moving forward," Millar said.

Explore further: Researchers regrow hair on wounded skin

Related Stories

Researchers regrow hair on wounded skin

November 28, 2018
By stirring crosstalk among skin cells that form the roots of hair, researchers report they have regrown hair strands on damaged skin. The findings better explain why hair does not normally grow on wounded skin, and may help ...

Activating pathway could restart hair growth in dormant hair follicles

December 5, 2013
A pathway known for its role in regulating adult stem cells has been shown to be important for hair follicle proliferation, but contrary to previous studies, is not required within hair follicle stem cells for their survival, ...

Synthetic sandalwood found to prolong human hair growth

September 19, 2018
A team of researchers led by Ralf Paus of the University of Manchester has found that applying sandalwood to the scalp can prolong human hair growth. In their paper published in the journal Nature Communications, the group ...

The human 'hairless' gene identified: One form of baldness explained

April 1, 2014
It's not a hair-brained idea: A new research report appearing in the April 2014 issue of The FASEB Journal explains why people with a rare balding condition called "atrichia with papular lesions" lose their hair, and it identifies ...

How skin begins: New research could improve skin grafts, and more

September 14, 2018
University of Colorado Boulder researchers have discovered a key mechanism by which skin begins to develop in embryos, shedding light on the genetic roots of birth defects like cleft palate and paving the way for development ...

Recommended for you

Researchers use computer model to predict prostate cancer progression

December 12, 2018
An international team of cancer researchers from Denmark and Germany have used cancer patient data to develop a computer model that can predict the progression of prostate cancer. The model is currently being implemented ...

New understanding of mysterious 'hereditary swelling'

December 12, 2018
For the first time ever, biomedical researchers from Aarhus University, Denmark, report cellular defects that lead to a rare disease, hereditary angioedema (HAE), in which patients experience recurrent episodes of swelling ...

Receiving genetic information can change risk

December 11, 2018
Millions of people in the United States alone have submitted their DNA for analysis and received information that not only predicts their risk for disease but, it turns out, in some cases might also have influenced that risk, ...

HER2 mutations can cause treatment resistance in metastatic ER-positive breast cancer

December 11, 2018
Metastatic breast cancers treated with hormone therapy can become treatment-resistant when they acquire mutations in the human epidermal growth factor receptor 2 (HER2) that were not present in the original tumor, reports ...

How glial cells develop in the brain from neural precursor cells

December 11, 2018
Two types of cells are active in the brain: nerve cells and glial cells. Glial cells have long been regarded primarily as supportive cells, but researchers increasingly recognize that they play an active role in the communication ...

Big datasets pinpoint new regions to explore the genome for disease

December 10, 2018
Imagine rain falling on a square of sidewalk. While the raindrops appear to land randomly, over time a patch of sidewalk somehow remains dry. The emerging pattern suggests something special about this region. This analogy ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.