SAN DIEGO, Calif. — Goose bumps make your hairs stand on end. This condition may also have a side benefit. It can help hair grow, a new study finds.
Nerves and muscles that raise goose bumps in the skin also stimulate some other cells to make hair follicles and grow hair. Those other stem cells are a type of unspecialized cells. They have the capacity to mature into several different types of cells.
Ya-Chieh Hsu is a stem cell researcher at Harvard University in Cambridge, Mass. She reported the findings December 9, here. She was speaking at a joint meeting of the American Society for Cell Biology and the European Molecular Biology Organization. Getting goose bumps when it’s cold, she suspects, might prompt animals’ fur to grow thicker.
The body’s sympathetic nervous system controls a lot of important body functions that we don’t think about. These include heart rate, the dilation of the eyes’ pupils and other automatic processes. The sympathetic nerves nestle next to the stem cells that can eventually create hair follicles, Hsu and her team found. Usually nerves are wrapped in a protective coat of myelin (MY-eh-lin). It’s like your home’s electrical wires that come sheathed in plastic.
But Hsu’s group found that the end of those nerves are naked where they meet the hair-follicle stem cells. It’s like the ends of your home’s wiring that are stripped of their plastic coat so that the wires can be wrapped around the contacts of plugs, switches, junction boxes or other electrical parts.
The nerves secrete norepinephrine (Nor-ep-ih-NEF-rin), the researchers found. That hormone was already known to be important for many involuntary reactions in the body. It plays a role, for instance, in your heart beat speeding up when you’re scared or nervous. Hsu’s group discovered the hormone also is necessary for hair growth. This finding might help explain why hair loss is a side effect of heart drugs known as beta-blockers; after all, they interfere with this hormone’s action.
Sympathetic nerves next to hair follicles also are wrapped around tiny arrector pili (Ah-REK-tor Pill-ee) muscles. When these muscles contract, they make hair cells stand on end. That’s what causes goose bumps.
Mice with gene changes that kept these muscles from growing lacked the sympathetic nerves. They also didn’t grow hair normally. Men with male pattern baldness also lack arrector pili muscles in their scalps, Hsu notes. That suggests that sympathetic nerves and the muscles that cause goose bumps may also be important in that type of baldness.
Restoring the nerves and muscles in people without them may lead to new hair growth, she said.