Scientists discover never-before-seen type of brain cell

A stock illustration of astrocytes (in purple) interacting with neurons (in blue) — The new study changes our understanding of the role of supportive cells known as astrocytes in the brain.

(Image credit: JUAN GAERTNER/SCIENCE PHOTO LIBRARY via Getty Images)

Scientists have identified a never-before-seen type of cell that may help to heal brain damage — at least in mice.

The researchers discovered a unique kind of astrocyte, a star-shaped cell that supports communication between brain cells, or neurons, and keeps them healthy by stabilizing the brain's protective barrier and regulating neurons' balances of charged particles and signalling molecules.

In the brain, astrocytes either live in gray matter, which contains the main part of neurons that holds DNA and enables the cells to process information, or white matter — the insulated wires that extend from some neurons. Researchers have long-studied the role of gray-matter astrocytes, but until now, less was known about their white-matter counterparts.

In the new study, published Monday (Feb. 24) in the journal Nature Neuroscience, scientists determined the function of white-matter astrocytes in tissue samples from the brains of mice. They did this by analyzing the activity of the genes these cells expressed, or "switched on."

The researchers identified two distinct types of white-matter astrocytes. The first performed the role of a "housekeeper," which physically supported nerve fibers and aided neurons in communicating with one another. Meanwhile, the second type performed a function that was previously unheard of for an astrocyte in the white matter — it had a unique ability to proliferate, thus making new astrocytes.

"That is a really important finding because that wasn't known before," study co-author Judith Fischer-Sternjak, the deputy director of the Institute of Stem Cell Research at Helmholtz Munich in Germany, told Live Science.

The researchers also found that some of these special, proliferative astrocytes were able to move from white matter to gray matter regions of the mouse's brain. This finding suggests that these cells may act as a reservoir for new astrocytes.

A high-resolution, fluorescent microscope image of astrocytes in the brain. The astrocytes are shown in red and green and the proliferative ones are also white. They look like blobs against a black background. — A high-resolution microscope image of proliferative astrocytes (shown in green and white) in the white matter region of a mouse brain.

If similar astrocytes are discovered in the human brain, the research could potentially lead to the development of new therapies to repair the brain after injury or damage, such as that caused by neurodegenerative diseases like multiple sclerosis, the authors suggested. For instance, scientists could theoretically learn to manipulate astrocytes so they're more likely to proliferate and replace defective or lost cells, Fischer-Sternjak said.

In the study, the researchers also looked at human brain tissue samples, which were extracted during the autopsies of 13 organ donors. While the team did identify white-matter astrocytes within these samples, these cells only expressed genes involved in housekeeping functions, rather than proliferation.

It's possible that the human brain samples didn't contain these unique proliferating astrocytes because they were collected exclusively from older patients, and the mouse experiments showed that proliferative astrocytes appear to decline in number with age, Fischer-Sternjak said.