Pulling every hair out led to every hair coming back, but no extra regeneration. The researchers showed that the level of inflammation under the skin was finely tuned to the scale of the damage. And through a cascade of chemical signalling and immune responses, this controlled the amount of regeneration. The team say it is like each hair gets a vote about what happens next and when it reaches a critical threshold it can trigger regeneration.
They call the concept "quorum sensing". Lead researcher Dr Cheng-Ming Chuong said: "It is a good example of how basic research can lead to work with potential translational value. What the findings means for people plucking their eyebrows is uncertain. The idea of quorum sensing is smart. But it is not known whether it will cure human baldness. Plucking the hair will indeed get rid of the gray — but only temporarily. And you don't need to worry that pulling out the gray hair will somehow summon more grays to magically appear.
That's because melanogenesis the process by which hair follicles make the pigment that gives hair its color is not totally consistent from hair to hair," he said. And there's also a third option here, of course: Ignore the gray and keep right on ignoring, until you have a head full of gorgeous gray hair. IE 11 is not supported. However, when they plucked hairs from a diameter of 3mm, they found around grew back.
The new hairs grew back in the plucked area, but also nearby. When they plucked hairs from a diameter of 5mm, this regenerated 1, hairs. Based on these biological observations, the researchers believe each hair follicle was acting as a sensor for a wider skin area to assess the level of damage through hair loss.
Input from each follicle fed into a collective biological circuit, which was able to quantify injury strength. Once a threshold was reached, a regeneration mechanism was activated. This type of system is often referred to as quorum sensing. The researchers made no mention of the human implications of this study. They concluded that the sense and response system they uncovered "is likely to be present in the regeneration of tissue and organs beyond the skin".
This study showed that hair regeneration in mice depends on the density at which hairs are removed. The researchers describe a sense and response mechanism working around a threshold.
If hair removal, specifically plucking, was below this threshold, there was no biological response to repair and regrow the hair, and the mice remained bald. But once the plucking threshold was crossed, the plucked hair regrew — and often more hair regrew than was there originally. The main limitation with this research is it did not involve humans, so we don't know whether the same thing would happen in people.
It might actually be unlikely. For example, people with trichotillomania , a condition where they impulsively pull out their hair, end up with patches of hair loss and balding that does not regrow.
There may be specific stress-related reasons why this is the case, but it is a reminder not to take these mouse results at face value. It is certainly too early to advise hair plucking as a cure for baldness, as the Daily Mail's headline suggests.
That may do more harm than good. The "cure for baldness" headline is also misguided, as the study was about hair regeneration after recent plucking. The findings are less relevant to those with longer-term hair loss, either in mice or people. Philip Murray of Dundee University, one of the authors of the study, summed this up in The Guardian when he said: "It would be a bit of a leap of faith to expect this to work in bald men without doing more experiments.
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