The brain attempts to repair itself following damage such as that caused by a stroke, and researchers continue to discover more about these processes, many of which are still comparatively poorly understood. The near term goal here is to manipulate the underlying biochemistry in order to spur much greater regeneration, possibly not just following injury, but also as a way to offset some of the impact of aging on the brain:
A previously unknown mechanism through which the brain produces new nerve cells after a stroke has been discovered. 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. 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. "Interestingly, even when we blocked the signalling mechanism in mice not subjected to a stroke, the astrocytes formed new nerve cells. 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."
"One of the major tasks now is to explore whether astrocytes are also converted to neurons in the human brain following damage or disease. Interestingly, it is known that in the healthy human brain, new nerve cells are formed in the striatum. The new data raise the possibility that some of these nerve cells derive from local astrocytes. If the new mechanism also operates in the human brain and can be potentiated, this could become of clinical importance not only for stroke patients, but also for replacing neurons which have died, thus restoring function in patients with other disorders such as Parkinson's disease and Huntington's disease."