The adult brain may have a greater ability to repair itself after injury or certain autoimmune diseases than scientists previously believed. In experiments with mice, researchers at the University of Zurich discovered that specialized support cells can repopulate damaged parts of the brain in an unusual way. Instead of moving whole new cells to the affected area at first, they send newly formed cell nuclei there.
Glial cells perform essential support and nutrition functions in the brain. One type, known as astrocytes because of their star-shaped appearance, is especially important for the healthy functioning of neurons. Astrocytes provide nutrients to nerve cells, help control blood flow, and support the overall health of brain tissue.
Scientists had long thought that once astrocytes were destroyed, the adult brain could not fully replace them. This loss can occur after brain injuries and in autoimmune diseases such as the rare spectrum disorder neuromyelitis optica, in which the body’s own antibodies attack and destroy astrocytes.
Specialized astrocytes rebuild damaged brain tissue
A study led by co-authors Marina Herwerth and Matthias Wyss from the Institute of Pharmacology and Toxicology at the University of Zurich (UZH) challenges that long-held view. The research team, led by Bruno Weber, identified a specialized population of “regenerative” astrocytes in the brains of living mice.
These cells gather around the edges of damaged brain regions and help rebuild the lost astrocyte network. “The findings of our study reveal a previously unknown ability of the adult brain to repair itself. They point to new ways to support recovery from ailments that involve the loss of astrocytes,” says Weber.
New cell nuclei travel to damaged areas
To follow the repair process, the researchers used two-photon microscopy to observe the brains of living mice in real time over several weeks. They also tracked which genes were activated in different regions of the brain. Together, these methods allowed the team to identify the astrocytes responsible for restoring injured tissue.
Regenerative cells do more than just divide. They also carry out an unusual process in which newly created nuclei from daughter cells travel considerable distances through astrocytes to the damaged region. As Weber explains, “they send the newly formed nuclei of their daughter cells gliding across long distances to repopulate the damaged area of the brain and reattach the astrocyte network.”
New targets for brain regeneration
The finding that cell nuclei can move through the long extensions of adult astrocytes to injured tissue adds a new dimension to scientists’ understanding of how the brain organizes its own repair after certain types of damage.
If researchers eventually learn how to selectively activate these repair mechanisms, they could promote more effective restoration of damaged brain tissue, rebuild astrocyte networks, and improve recovery from certain brain disorders.
The team also identified many genes and signaling pathways that are temporarily activated while the repair process is underway. These biological signals may provide potential targets for future efforts to influence regeneration after disease or injury.
“We have been able to identify numerous genes and signaling pathways that are temporarily activated during repair. In the future they could serve as a starting point to influence regeneration processes after diseases and injuries,” emphasizes Weber.