Scientists discover ‘part-time cleaners’ in the brain

(ORDO NEWS) — Usually, when “garbage” is formed in the nervous system – for example, a nerve cell dies – microglia cells take care of its removal.

However, if the cell of the microglia itself dies, the “colleagues” do not remove it. Now scientists have finally found out who is doing the “cleaning janitors”, while not forgetting to perform their main functions.

Microglia are the immune cells of our nervous system, involved in the formation and maintenance of contacts between neurons and the removal of foreign substances and objects, whether they are pathogens that have invaded the brain or simply dead cells.

However, the microglial cells themselves are not eternal: they regularly die, after which the dead cells must be removed from the nervous system by someone else.

The fact is that the microglial cells themselves do not perceive their own kind as “garbage”, but the rate of their death can be enormous: in just a few days, up to 95 percent of all brain microglia can be updated. So who does not allow a whole “mountain” of dead cells to accumulate in our brain?

To find out, a group of Chinese scientists tracked what happens to dead microglial cells in mice. Since under normal conditions only about 30 percent of microglia, or 0.1 percent per day, is renewed per year, scientists had to inject animals with a drug that can accelerate the death of microglial cells, and track the work of all other types of brain cells to understand who is doing ” cleaners cleaning.

It turned out that this function was taken over by astrocytes , which already perform a variety of tasks in the nervous system: from maintaining neurons and dividing them into compartments to storing nutrients and releasing neurotransmitters.

But normally, astrocytes are not engaged in the removal of dead cells – this is the task of microglia: only if the main “wipers” do not cope, these cells take “part-time work”.

Scientists discover part time cleaners in the brain 2
The astrocyte ( green ) already has a lot of tasks to ensure the normal functioning of neurons ( red ), but now another function has been added to them

The scientists also found that astrocytes don’t simply engulf microglial cells – they need helpers, namely, C4b opsonin proteins that attach to the surface of dead microglial cells, “informing” that they need to be removed.

Once the astrocyte has engulfed the desired cell, it is broken down by enzymes into molecules that can already be used to create new microglial cells and restore balance in the nervous system.

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