A stem cell research project takes an unexpected turn

Valerie Horsley and her fellow researchers at Yale University were looking at the role fat cells play in the skin, part of a broader examination into how tissues maintain themselves, when their work took them in a totally unexpected direction: Now they’re looking at a potential treatment for baldness.

“I was really surprised that this is the direction we’re going in,” said Horsley, a professor of molecular, cellular and developmental biology at Yale University. “That’s the exciting thing about science. You get to study things you never dreamed you would be doing.”

Valerie Horsley

Horsley and the team of researchers found that they could trigger hair growth in mice using stem cells from the fatty layer of skin. They identified the stem cells and found that they produce molecular signals that are necessary for hair growth.

Their research is being published today in the journal Cell, and Horsley says the findings could hold promise for therapies for alopecia and baldness.

“If we can get these fat cells in the skin to talk to the dormant stem cells at the base of hair follicles, we might be able to get hair to grow again,” she said.

Don’t expect to see fat-laden hair-loss cures on store shelves anytime soon; any potential real-world applications are likely years away. Similar hair growth-inducing signals remain to be identified in humans.

But the findings changed the direction of Horsley’s lab. Her main research interest is in how tissues maintain themselves. From her perspective, disease is a problem of the tissue; a person becomes sick when their tissues don’t work.

“Bodies have the natural ability to repair themselves in general, so if we can somehow capitalize on that and make that better, then I feel like we can prevent disease,” she said.

The hair growth work started with an interest in what fat cells do in the skin. Horsley said she, like most researchers in the field, had paid little attention to the skin’s fat cells, aside from a few publications about them in the 1930s.

Horsley’s team’s work began with the observation that when hair is dead, the layer of fat in the skin is very thin. When hair starts to grow, the fat gets very thick. “We were interested in how that change is happening,” she said.

There are two ways the fatty layer could get bigger: Either individual fat cells get larger, or more fat cells get made. Horsley’s team found it was the latter–when hair starts to grow, new fat cells are made.

They explored further using mice with defects in different types of fat cells. Mice without mature fat cells in the skin could grow hair relatively normally, but mice with defects in their immature fat cells could not, suggesting that it’s the immature fat cells that play a role in activating hair growth. That indicated that it’s the turnover and growth of fat cells that’s important in driving hair to grow, Horsley said.

The team also transplanted the fat stem cells into mice that had decreased fat cells and abnormal hair growth. After the transplants, their hair grew.

The team theorized that the fat stem cells produce signaling molecules that communicate with cells in the hair. One, called platelet derived growth factor, is highly expressed in immature fat cells.

The Cell article was authored by Eric Festa, Jackie Fretz, Ryan Berry, Barbara Schmidt, Matthew Rodeheffer, Mark Horowitz, and Horsley. The research was funded with money from Yale and the National Institutes of Health.

In the article, the authors noted that patients with obesity, anorexia and lipodystrophy–a disturbance in the way the body produces, uses and stores fat–have defects in their hair follicle growth.

Horsley said the fact that the role fat cells play in skin can be shown means that researchers can now look at whether they are important in other skin processes, like wound healing or tumor formation.

“Now we have the tools to really ask those questions,” she said.