Hairs Send Signals to Each Other About When to Grow

We might be able to determine why people go bald, according to a new study.

The study found that coupling inhibitors and activators with the physical growth of hair follicles is sufficient to kick start periods of hair growth and excite hair regeneration. Maksim Plikus at the University of California, Irvine said the follicles send signals to each other about growth.

“Think of it like in track and field when people run and pass the baton,” he said to New Scientist. “One runner is an active hair follicle and is passing off an activating signal to another hair follicle.”

Hair doesn’t grow continually. Instead, follicles cycle through growing, dying and resting. Prior research found hair follicles to have chemical signaling pathways known as WNT and BMP that help to regulate hair growth in mice.

Plikus and his research team used mathematical modeling in their recent study to determine whether WNT and BMP signals play a role within the entire body. What they found was that the signals explain the growth cycles of every hair on the body of a mouse.

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The study said communication between the signals suggests that follicles all over the body utilize the same language to arrange growth cycles. WNT waves kick-start follicle growth, while BMP stops growth by signaling a stem cell shut down in follicles.

For example, the ear skin of the mice contained hair follicles in an extended rest phase, while chin hairs were in a state of fast-cycling of growth, dying and rest. Understanding how the follicles operate within certain areas of the body could lead to understanding how they operate in other areas, the study said.

“Hair growth stops at the boundaries with hyper-refractory ears and anatomically discontinuous eyelids, generating wave-breaking effects,” the researchers wrote. “We posit that similar mechanisms for coupled regeneration with dominant activator, hyper-refractory and wave-breaker regions can operate in other actively renewing organs.”

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The study was able to accurately predict hair growth patterns across the body of an entire mouse for the first time. Plikus said he and his team hope to use the study as a base to regulate the signals with drugs that could send waves of growth into balding areas.

“We now have a road map to optimize the levels of activators and inhibitors to achieve desired hair growth,” Plikus said.