I believe that everyone and The Odd Dot cake have heard the story of “One Night WhiteHead”, such as encountering some major blows, or suddenly encountered difficulties, “as if overnight years old.” This is certainly an exaggerated rhetoric, but in real life, because of these pressures lead to young white hair is not exaggerated. Although everyone is so passed, but in the end the pressure is not really leading to white hair?
A recent study by Harvard researchers, published in the journal Nature, tells us that this is true. In addition, they revealed the mechanism through mouse experiments, which, it turns out, that stress activates the sympathetic nervous system, produces norepinephrine, over-proliferation and premature depletion of melanin stem cells, resulting in a lack of melanin in subsequent hairs.
Melanin stem cells (red) and sympathetic nerves (green)
Here’s a simple insertion of a small kop, and there are two types of stem cells in our hair follicles: hair follicle stem cells and melanin stem cells. Most of the time, these stem cells are dormant and only activate early in life, with new black hair.
In the process, melanocytes differentiate into melanogenesis-producing cells that “stain” new hair. Understand this knowledge point, we should be able to understand the mechanism just introduced by The Odd Cake.
In fact, at the beginning of this research, the researchers did not touch the right way. They first assumed that stress would induce the immune system to attack melanin stem cells, but the results rejected that hypothesis.
Later, they speculated that cortisol, a hormone secreted in large quantities under stress, was at work. However, mice that had their adrenal glands removed and were unable to produce cortisol still had white hair under pressure.
Two of the most questionable reasons were denied, and the researchers had to rule out each one by one to find the right answer.
First, they chose three methods to simulate physiological or psychological stress in mice, and in all three groups of mice, researchers detected high levels of cortisol (equivalent to human cortisol) and norepinephrine, suggesting that all three groups produced a classic stress response.
In three groups, mice in the pressure group induced by the capsaicin analogue, resin toxin (induced by pain-induced stress), were the most rapid and obvious to produce white hairs, with many white hairs growing during the next hair growth cycle after injection, while the other two groups took 3-5 cycles to achieve this effect. This also shows that any form of pressure can lead to the production of white hair.
Comparison of hairs in injected saline and resin toxin (RTX) mice (true spicy to faded)
The immediate cause of newborn hair is white is generally dependent on melanin synthesis defects, the lack of differentiated melanin-producing cells, and the failure of melanin stem cell dryness to maintain these three reasons. So, next, the researchers studied the lineage of melanocytes. In the early stages of hair growth, they injected mice with resin toxins, in which melanocytes and melanocytes were present at the same time.
After injecting resin toxins, the researchers found that the number of melanin stem cells decreased significantly, and that many of the melanin stem cells in hair follicles disappeared completely within five days, but the differentiated melanogen-producing cells had no effect and continued to produce melanin. By the time the next hair growth phase approaches, the “reserve” of melanin stem cells is missing a lot and white hair is abundant.
It seems that the pressure is to “destroy” melanin stem cells to cause white hair, so the next step is to find out how pressure destroys melanin stem cells.
Under stress, both humans and mice, there will be an increase in stress hormones (cortisol/cortisol) and norepinephrine, which in previous experiments have ruled out cortisol, so will norepinephrine be the real cause?
They removed the norepinephrine receptors from the melanin stem cells and injected the mice with resin toxins, which produced no white hair. This suggests that norepinephrine is the “real culprit” of understressed, melanin stem cells.
Norepinephrine comes from two sources, the adrenal gland and the sympathetic nervous system. The results of the experiment have shown that removing the adrenal glands is not possible to prevent the mice from turning white at stress. That’s the only sympathetic nervous system left, which can also be activated when stress is generated, mainly to control the stress response of combat or flight.
The researchers found that it was stress that activated the sympathetic nervous system, producing large amounts of norepinephrine, and pushing melanocystin stem cells into a rapid abnormal proliferation state. On the third day after the resin toxin was injected, many melanin stem cells completed the proliferation-differentiation-migration-staining process in new hairs, after which there was no store of melanin stem cells.
Even without pressure sources, the sympathetic nervous system was activated, and they also observed the production of white hair in mice.
Melanin stem cells (yellow) and sympathetic nerves (purple) under another staining method
The good news, however, is that the researchers compared the gene expression profiles of mice injected with resin toxins and placebos, and found that the most varied expression under stress-induced expression was the genes that encode cell-cycle protein-dependent kinase (CDK). When they treated stressed mice with CDK inhibitors, the mice did not produce white hair as expected by the researchers.
‘We all know that surrounding neurons regulate organ function, blood vessels and immunity, but little attention is paid to how they regulate stem cells, ‘ the researchers said. Through this study, we learned that neurons can control stem cells and their functions, linking stress to white hair.
They also point out that the study did not address the causes of interactions between the sympathetic nervous system and melanocystin stem cells, which requires more research later. Of course, the findings in mice need to be replicated in humans, and whether their methods in the experiment can prevent the effects of stress on melanin stem cells and avoid the production of white hair caused by excessive stress.
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