One of the foundations of surgery is that doctors must create trauma to heal trauma. The same may now be said for male pattern baldness, as researchers from the University of Southern California have found through plucking mouse hairs that new hair started to grow back even thicker.

The study is published in the journal Cell and relies on a microbiology technique called quorum sensing, a process of stimulus and response related to population density. In this case, scientists found that plucking many hairs within a specific patch signaled injury to the nearby follicles and actually caused the follicles of the thinning hair to regenerate thicker hair growth.

“It is a good example of how basic research can lead to a work with potential translational value,” said Dr. Cheng-Ming Chuong, a professor of pathology at the Keck School of Medicine of USC, in a statement. “The work leads to potential new targets for treating alopecia, a form of hair loss.”

Androgenetic alopecia, better known as male pattern baldness, accounts for some 95 percent of the hair-loss cases in the U.S. The American Hair Loss Association estimates that roughly two-thirds of men will experience some degree of hair loss by age 35, and 85 percent will experience significant thinning by age 50. There is no cure.

Research into quorum sensing for hair growth began two years ago when the study’s first author, Chih-Chiang Chen, a dermatologist, arrived at USC with the knowledge that hair follicle injury affects the follicles in the surrounding area. Meanwhile, Chuong had found through prior studies that this kind of injured environment was capable of regenerating hair growth. So, they joined forces and decided to test whether plucking thinning hairs could actually regenerate new, healthier hair.

From the back of a mouse, Chen plucked 200 hairs. Those he plucked from a low-density patch didn’t result in regenerated hair. But when he focused on the hairs within a three- to five-millimeter radius, 450 to 1,300 hairs grew in their place. Some even grew back outside the plucking radius.

Quorum sensing, in this instance, involves the injured follicles releasing inflammatory proteins that get immune cells rushing to the site. These cells secrete signaling molecules that stimulate growth in both plucked follicles and unplucked follicles. According to Chuong, the principal not only has applications to male pattern baldness, but possibly other locations that need regeneration.

“The implication of the work is that parallel processes may also exist in the physiological or pathogenic processes of other organs,” he said, “although they are not as easily observed as hair regeneration.”

Source: Chen C, Wang L, Plikus M, et al. Organ-Level Quorum Sensing Directs Regeneration in Hair Stem Cell Populations. Cell. 2015.