The brain evidently can regenerate itself better than previously assumed after injuries or certain autoimmune diseases. Using a mouse model, researchers at the University of Zurich have demonstrated that special supporting and nourishing cells repopulate damaged areas of the brain by initially sending only newly formed cell nuclei there.
Glial cells are supporting and nourishing cells in the brain. Star-shaped glial cells called astrocytes are vital to the functioning of neurons. They supply the nerve cells with nutrients, help to regulate blood flow and keep brain tissue healthy. It had long been assumed that when astrocytes are lost – as happens, for instance, in brain injuries or autoimmune diseases such as rare neuromyelitis optica spectrum disorder, in which the body's own antibodies destroy these cells – the adult brain cannot fully replace them.
Regenerative astrocytes repair damaged tissue
A new study by co-lead authors Marina Herwerth and Matthias Wyss from the Institute of Pharmacology and Toxicology at the University of Zurich (UZH) has now overturned that assumption: their research team headed by Bruno Weber discovered a specialized group of "regenerative" astrocytes in the brains of living mice that step in on the perimeter of the damaged area of the brain to rebuild the cells. "The findings of our study reveal a previously unknown ability of the adult brain to repair itself. They point toward new ways of supporting recovery from ailments involving the loss of astrocytes," Weber says.
Only cell nuclei migrate
The researchers used two-photon microscopy to observe the brains of living mice in real time over a period of several weeks and mapped which genes switch on in which areas of the brain. This way they were able to identify the special astrocytes that take care of rebuilding injured tissue. But those cells don't just divide, they also perform a remarkable feat: "they send the newly formed nuclei of their daughter cells gliding across long distances to repopulate the damaged area of the brain and knit the astrocyte network back together," Weber explains.
Starting points for targeted regeneration
The discovery of how adult brain cell nuclei migrate through the long star-shaped extensions of astrocytes to injured tissue expands comprehension of how the brain organizes and regenerates itself after certain injuries. If those mechanisms can be selectively activated, that could help to more effectively repair damaged brain tissue, restore astrocyte networks and thus improve recovery after certain brain disorders. "We were able to identify numerous genes and signaling pathways that are temporarily activated during repair. They could serve as starting points in the future for influencing post-disease and -injury regeneration processes," Weber stresses.
