Dead cells are removed from the body in a surprisingly cannibalistic way: ScienceAlert

A million cells in your body die every single second. So where does all the trash go?

A new study reveals a surprisingly cannibalistic cleanup method. Some dead stem cells in mammalian bodies appear to become food for their neighbors, researchers in the US have found.

These living stem cells are attracted to the “smell” of a freshly created corpse by two sensitive receptors that are spatially tuned to the “smell” of death and life.

“[The mechanism] “It only works if each receptor receives the signal to which it is tuned,” explains cell biologist Katherine Stewart from Rockefeller University in the USA.

“If one of them disappears, the mechanism stops working. This is a really nice way to keep the area clean without using up healthy cells.”

The study was carried out on the hair follicles of mice in the final stages of life.

Previous studies have shown that when cell death is widespread in the mouse hair bulb, it is cells in the lower outer shell that eliminate the corpses.

But until now it wasn’t clear what happened when death reached the follicle stem cells.

In experiments, Stewart and her colleagues have shown that when hair follicle stem cells (HFSCs) die, they are quickly eaten by their neighbors before immune cells, such as macrophages, can step in and do the same.

“I was very surprised to find that the hair follicle stem cells were actually the first responders, especially because mouse skin is pretty well endowed with macrophages, so they’re not even that far away,” says Stewart.

It appears that HFSCs protect each other from an overactive immune system by fighting off inflammation.

When HFSCs are unable to eat each other, their corpses disrupt the long-term maintenance of the stem cell pool.

In contrast, in cases where they can eat each other, some HFSCs eat up to six of their dying neighbors.

Eating the dead could be a way to convert fuel into energy, explains cell biologist Elaine Fuchs, who runs the Rockefeller lab, “but once the debris is cleared, they must quickly get back to their work of maintaining the stem cell pool and. “ produce the hair of the body.

The entire process appears to be carefully controlled via two receptors on HFSCs that function like “on” and “off” switches. A receptor responds to a “find me” lipid signal emitted by a dying neighbor. The other responds to a growth-promoting retinoic acid released by other healthy cells.

“A dying cell triggers the mechanism, and when there are no more dead cells, the lipid signal disappears and only the retinoic acid signal from the healthy cells remains,” says Stewart.

“This tells the program to turn the volume down again. It’s so elegant in its simplicity.”

The researchers speculate that this rapid detection of cadaver cells could also work in other tissues in the mammalian body, although further research is now needed to test this idea.

Regardless, the team argues that their discovery represents a “powerful mechanism to quickly eliminate dying cells and prevent tissue damage.”

The study was published in Nature.