Mouse study: stress signals wake ancient viral DNA in follicle stem cells and trigger hair loss

Researchers working with mice have described a mechanism that links the sympathetic nervous system, the stress response and autoimmune hair loss, pravda.ru reports. In the experiments, cells of the body responded to nervous signals by imitating a viral infection and became a target of the animal's own immune system pravda.rupravda.rupravda.ruOpen source ↗. The work was carried out on mice.

The researchers focused on endogenous retroviruses. These are ancient genetic fragments that became embedded in the DNA of our ancestors millions of years ago. Under normal conditions they stay silent and do not interfere with the work of the body.

From stress signal to damaged follicle

The trigger for their activation turned out to be the sympathetic nervous system, which mobilizes the body under stress and uses the neurotransmitter norepinephrine. When norepinephrine acts on hair follicle stem cells in the phase of active growth, the viral fragments begin to produce proteins.

Viral particles inside a cell are a standard danger signal. The cell sends an alarm to its surroundings and switches on antiviral defence. There is no real infection, but T cells of the immune system see the markers of infection and attack the hair follicle, destroying the cells that drive hair growth pravda.rupravda.rupravda.ruOpen source ↗.

Role of regulatory T cells and control experiments

Earlier, regulatory T lymphocytes were thought to shield follicles passively. The new study indicates that this protection is an active process of suppressing the alarm. When these cells were removed, hair loss began only after the nervous system sent its signal and made the cells behave as if they were infected.

A further experiment supported this chain of events. When the scientists used antiviral drugs or blocked signals from nerve cells, the mice stopped losing hair even without immune protection. The cells simply stopped sending false distress signals.

The link between stress and hair loss has been noticed for a long time, and biologists have now described a specific molecular chain behind it. In people, alopecia is a multifactorial process, and the stress mechanism may be only one of its causes pravda.rupravda.rupravda.ruOpen source ↗. The results come from mice and have not been shown in humans.