Scientists have successfully grown new hair follicles from the skin cells of balding men. While the research team hasn’t yet shown whether the structures, which produce strands of hair on our bodies, are fully functional and usable for transplants onto a scalp, experts say the discovery is a significant step toward finding new treatments for hair loss.
“Their work is very elegant and extremely rigorous,” says Radhika Atit, a skin biologist at Case Western Reserve University in Cleveland, Ohio, who was not involved in the new study. “This is a big technical advance.”
Balding occurs when hair follicles stop producing new strands of hair in any area of the body. Now, taking drugs that prevent or slow the hair loss or transplanting hair follicles from one area of the body to another are the only viable treatments. Producing new hair follicles in the lab has not been an option—at least for human patients. In mice, researchers have shown that if they isolate dermal papilla cells, which surround hair follicles in the skin, grow them in petri dishes to produce new cells, and then put the cells back in the mouse, new hair follicles will develop. But when dermal papilla cells from humans are put into dishes in the lab, they lose their ability to induce the formation of new follicles.
Angela Christiano, a skin researcher at Columbia University who has discovered genes related to hair loss, recently brainstormed potential solutions to the problem with her colleagues. They noticed that while the dermal papilla cells from mice naturally formed large clumps in culture, the human cells didn’t. “We began thinking that maybe if we could get the human cells to aggregate like the mouse cells, that might be a step toward getting them to form new follicles,” Christiano says.
Her team decided to try a cell-growing approach, called 3D cultures, that’s been successful for other types of cells that need to form complex structures as they grow. The researchers collected dermal papilla cells from seven volunteers who had been diagnosed with male-pattern baldness. Rather than stick the isolated cells on a flat culture dish, they mixed the cells with liquid, then let the mixture hang in tiny droplets from a plastic lid, like condensation on the roof of a container. Because the cells inside the droplets are free-floating, the technique allows them to contact each other in every direction, as they would in the human body, rather than only touch side to side as they do in a flat dish. In the droplets, the cells behaved differently; as they divided to form new cells, they clumped into what the researchers call “spheroids”—balls of about 3000 cells.
To test whether the new spheroids were a better mimic for functional dermal papilla cells than those that had been grown in typical dishes, Christiano and her team determined what genes were turned on and off in different sets of dermal papilla cells. In cells grown on flat culture dishes, the expression of thousands of genes didn’t match up with their normal patterns, explaining why the cells from those dishes had been unable to generate new hair follicles. But in the 3D cultures, 22% of those genes had been restored to their correct on or off state.
The researchers then took 10 to 15 of the spheroids that had formed from each donor and sandwiched them between two layers of human skin that were grafted onto mice. Six weeks later, spheroids from five of the seven donors had coaxed the skin cells around them to start rearranging, forming the telltale shape of a hair follicle, the team reports online today in the Proceedings of the National Academy of Sciences. In two cases, hairs were even seen beginning to extend from the follicles, though the researchers didn’t continue the initial experiment for long enough to test whether the hairs were fully normal in terms of their ability to regrow.
Using one’s own cells to generate new follicles is useful because hair color and thickness will match perfectly with the rest of someone’s head of hair, Christiano notes. And with the new tissue culture technique, clinicians would be able to take just a few dermal papilla cells from a balding patient and expand the number of hair follicles available for transplant, rather than only be able to move follicles around. “Using this technique could change the number of people who would be eligible for hair transplants,” Christiano says.
The success of the approach is exciting, but the real breakthrough for other researchers in the field is the new data on gene expression in dermal papilla cells, says George Cotsarelis, a dermatologist at the University of Pennsylvania. The full readout of what genes are on and off in dermal papilla cells has never been collected before, so researchers now have a new list of thousands of genes to study further that may play key roles in hair follicle development. “It could have implications for not just hair, but treating wounds and scarring,” he says.
The spheroids capable of producing hair follicles could also be used as a new way to test drugs for their ability to restore follicle function, Atit says. “This is a better model system to use for drug testing than a two-dimensional plate.”