Cure for Baldness? Mouse Study Offers Hope

Stefan Lovgren
for National Geographic News

September 27, 2005

A new study of hair regrowth in mice offers some hope to millions of balding men and women that barren hair follicles could be rejuvenated.

To learn how a gene called Hairless regulates hair growth, scientists studied a line of completely bald mice that lacks the Hairless gene. These mice start with a full coat of fur, but once it falls out it never grows back.

By genetically engineering the hairless mice to produce Hairless protein in specific cells within their hair follicles, the scientists caused the mice to regrow thick fur.

Although hair growth in mice and humans is similar, baldness caused by mutations in the Hairless gene is a rare genetic disorder and is not directly related to common types of baldness, such as male pattern baldness.

But understanding the mechanisms by which hair normally regrows could help scientists figure what causes such cases of hair loss.

"Establishing this step-by-step process by which hair regrows will be useful for designing potential treatments for any type of baldness," said Catherine Thompson, a study author and neuroscientist at Johns Hopkins University School of Medicine in Baltimore, Maryland.

The research is published this week in the journal Proceedings of the National Academy of Sciences.

Hair Cycle

Hair follicles—skin cavities where individual hairs sit—are tiny organs that are able to regenerate themselves.

The hair growth cycle has several stages: growth, regression, rest, and reinitiation of growth. If something goes wrong with this process, hair thinning or baldness may result.

After hair grows to a particular length, it falls out and the lower part of the follicle is destroyed.

After a period of rest, however, the follicle receives a signal that tells it to regrow its lower part and produce a new hair. Until the new findings were made, the exact nature of that chemical signal remained unknown.

"It is important to understand the hair cycle because the timing of the signaling required to regenerate a hair follicle is critical," Thompson said.

The scientists focused on a gene known as Hairless, which encodes a protein that is essential for hair follicle regeneration. In humans and mice with mutations in the Hairless gene, hair growth is initially normal, but once hair is shed, it does not grow back.

Potential Treatment

The new study shows that the mechanism by which Hairless regulates hair regrowth is by controlling the timing of a key signaling pathway.

Hairless "turns off" a gene that makes a protein called Wise. In cells lacking Hairless, continual accumulation of Wise appears to prevent the hair cycle from switching from the rest to the regrowth phase.

"By turning off an inhibitory protein … Hairless turns on [this] signaling in the proper cells and at the proper time in the hair cycle … inducing hair regrowth," Thompson said.

Bald mice that were genetically engineered to produce the Hairless protein were able to regrow thick fur.

Lacking Hairless is a rare genetic disorder and is not the reason why a person goes bald. But the findings could help scientists better understand the signals guiding the regrowth of hair. This, in turn, could aid the development of potential treatments for baldness.

"Each step in the [hair cycle] process is two things: a step where something could go wrong to cause baldness, but also a step which you could potentially design a treatment that might circumvent whatever went wrong to cause baldness," Thompson said.

"There are certainly parts of the puzzle that remain to be solved," she added. "But this work has given us a better understanding of the molecular mechanisms, or step-by-step process, by which hair growth is regulated."

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