Discovered Mechanism Repairs Brain After Stroke

New research has discovered a mechanism through which
the brain produces new nerve cells after 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. A previously unknown mechanism through which the brain produces new nerve cells after a stroke has been discovered. The findings have been published in the journal Science.

The researchers 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.
 
The scientists could also identify 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. The new nerve cells were found to form specialized contacts with other cells. It remains to be shown whether the nerve cells are functional and to what extent they contribute to the spontaneous recovery that is observed in a majority of experimental animals and patients after a stroke.
 
A decade ago, the research group was the first to show that stroke leads to the formation of new nerve cells from the adult brain's own neural stem cells. The new findings further underscore that when the adult brain suffers a major blow such as a stroke, it makes a strong effort to repair itself using a variety of mechanisms.
 
The major advancement with the new study is that it demonstrates for the first time that self-repair in the adult brain involves astrocytes entering a process by which they change their identity to nerve cells.