Men who are not pleased with their balding head will be glad to know that researchers have found one potential way to make their hair regrow. The procedure, however, involves plucking hair out, which can be uncomfortable and even painful.

For the new study published in the journal Cell on April 9, a group of researchers were able to regenerate more than 1,000 hairs after they plucked 200. In a series of experiments involving mice, the researchers plucked 200 hairs following a specific pattern in a confined area, making sure that the neighboring hair was pulled out. They managed to regrow up to six times as many hair, including those beyond the plucked region.

Study researcher Cheng Ming Chuong from the Department of Pathology of the University of Southern California in Los Angeles, together with colleagues, found that removing the follicles from a circular patch of skin with a diameter of 6 millimeters (0.24 inch) did not result in regeneration. Removing 200 hairs from a 5 millimeter (0.20 inch) circular patch, on the other hand, led to the regrowth of 1,300 hair.

Plucking the same number of hair from a patch 4 millimeters (0.16 inch) in diameter regenerated 780 new hairs. Pulling each of the hair out resulted in every hair coming back albeit without extra regeneration.

Results of further experiment show that plucking the hair out triggers a chemical distress signal that informs the surrounding skin cells that they should start growing hair. The researchers said that every hair gets a vote on what would happen next. Regeneration is likewise triggered when a critical threshold is reached, a concept the researchers dubbed "quorum sensing."

"By coupling immune response with regeneration, this mechanism allows skin to respond predictively to distress, disregarding mild injury, while meeting stronger injury with full-scale cooperative activation of stem cells," the researchers wrote in their study.

The researchers said that the result of their experiments may pave the way for a potential treatment for alopecia. Chris Mason from the University College London described the idea of quorum sensing as smart, but he pointed out that it remains uncertain whether it will be able to cure human baldness.

"A lot of studies have produced hair, but it's too fine - it's baby hair, it's light-colored and it just doesn't look right," Mason said. "But here we can infer they are adult hairs so that is something that is a step change."

Photo: Sascha Kohlmann | Flickr