Baldness affects many people (mostly men) at some point in their lives and a lot of research has been carried out to learn how to prevent it. The secret to doing so might be the most ironic treatment ever: to prevent going bald, pluck your hair.
The science of hair growth is more fascinating than it may seem at first sight. Hairs actually go through cycles: first they grow thanks to the stem cells in the follicle (the anagen phase), then they stop growing (the rest phase), and lastly the hair falls out. But if you manually remove the hair at any of these phases, an interesting process is triggered. The follicle will release cytokines, specifically the CCL2 type, which is a chemical that attracts white blood cells. When these cells arrive, they also release their own set of chemicals that stimulate stem cells so they start producing hair again. However, what’s the point of plucking one hair so that it grows if you already have it?
Well, there’s a trick. Scientists at University of Southern California, Los Angeles, did some experiments with mice where they removed a handful of hair on a specific area of the mouse’s body, and to their surprise, found that not only did the patch of hair grow back, but also stimulated growth in others areas. The catch is that this only happened if a certain amount of hair was removed: there was a threshold for the amount of hair that needed to be pulled out for others to be stimulated.
This is because the CCL2 signal from one follicle isn’t very large; you need CCL2 to build up so the effects are much stronger and can affect a larger area of the skin. In the specific experiment they carried out, the lowest number of hairs that had to be removed was of 200, which lead to the growth of 1200 hairs. The way these hairs can communicate with each other by accumulation of chemical signals is called ‘quorum sensing’, and it causes the hairs to act like a collective group, as if taking decisions together.
Although the study was carried out on mice, the researchers don’t rule out the fact that it could somehow be used in humans, although some modification may be necessary. It also shows the increasing complexity of the immune system, and possibly sheds some light as to how the mechanism of regeneration is controlled.