Cells that repair brain after stroke discovered

Scientists have discovered a previously unknown mechanism through which the brain produces new nerve cells after a stroke.
A stroke is caused by a blood clot blocking a blood vessel in the brain, which leads to an interruption of blood flow and therefore a shortage of oxygen. Many nerve cells die, resulting in motor, sensory and cognitive problems.
Researchers at Lund University and Karolinska Institutet in Sweden have shown that following an induced stroke in mice, support cells, so-called astrocytes, start to form nerve cells in the injured part of the brain.
Using genetic methods to map the fate of the cells, the scientists could demonstrate that astrocytes in this area formed immature nerve cells, which then developed into mature nerve cells.

"This is the first time that astrocytes have been shown to have the capacity to start a process that leads to the generation of new nerve cells after a stroke," said Zaal Kokaia, Professor of Experimental Medical Research at Lund University.
The scientists also identified the signalling mechanism that regulates the conversion of the astrocytes to nerve cells.

In a healthy brain, this signalling mechanism is active and inhibits the conversion, and, consequently, the astrocytes do not generate nerve cells.
Following a stroke, the signalling mechanism is suppressed and astrocytes can start the process of generating new cells.
"Interestingly, even when we blocked the signalling mechanism in mice not subjected to a stroke, the astrocytes formed new nerve cells," said Kokaia.

"This indicates that it is not only a stroke that can activate the latent process in astrocytes. Therefore, the mechanism is a potentially useful target for the production of new nerve cells, when replacing dead cells following other brain diseases or damage," said Kokaia.
The findings have been published in the journal SCIENCE.