In what may be one of the most significant discoveries in neurodegenerative disease, researchers have found that brain cells, called astrocytes, contribute to killing neurons and myelin-forming oligodendrocyte cells, which may drive neurodegenerative diseases such as multiple sclerosis (MS).
Experiments indicate an aggressive astrocyte type kills cells by secreting a yet-unidentified factor. Researchers are working to identify the secreted molecule, as well as to determine how to stop good astrocytes from becoming bad. Doing so may help them interfere with the neurodegeneration that occurs in MS and other conditions.
The study that explains the discovery, “Neurotoxic reactive astrocytes are induced by activated microglia,” was published in the journal Nature.
“We’ve learned astrocytes aren’t always the good guys,” Ben Barres, MD, PhD, the study’s senior investigator, said in a press release. “An aberrant version of them turns up in suspicious abundance in all the wrong places in brain-tissue samples from patients with brain injuries and major neurological disorders from Alzheimer’s and Parkinson’s to multiple sclerosis.”
Barres called the finding the “the most important discovery my lab has ever made.”
Astrocytes are key players in forming and modulating connections and communications between neurons. In the absence of disease or injury, the cells are referred to as “resting astrocytes” — a somewhat contradictory term given the huge amount of work they do.
Under certain circumstances, astrocytes change their appearance and behavior, becoming “reactive.” The star-shaped cells have been the focus of extensive research efforts, and in 2012, the research team at Stanford University School of Medicine discovered two types of reactive astrocytes. The cells are formed when exposed to different factors. Those that researchers called A1 developed when resting astrocytes were exposed to components simulating a bacterial infection. A2 cells, in contrast, emerged after oxygen deprivation, which can occur during a stroke, for example.
A2 astrocytes have regenerative properties, but the A1 type spews out large amounts of pro-inflammatory factors.
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