Image of brain. Credit: Lund University

Scientists working at Lund University and Karolinska Institutet in Sweden  made an astounding breakthrough this week. They managed to identify a previously unknown mechanism in the brain. And it just happens to be the mechanism through which the brain produces new nerve cells after a stroke.

The findings have been published in the journal Science, and they open a number of doors for advanced medical treatment.

There is often a bit of confusion between a stroke and a heart attack; however, the difference is really quite simple—a heart attack takes place where there is a blockage in (you guessed it) the heart; a stroke is caused by a blood clot blocking a blood vessel in the brain. Ultimately, this blockage in the brain causes an interruption of blood flow and a shortage of oxygen. As soon as the brain is deprived of oxygen, nerve cells start to die (in other words, your brain begins to die).

The knock on effects are often far reaching. A stroke can cause loss of movement, loss of speech, loss of hearing—it impacts any and all motor, sensory, and cognitive processes.

The Discovery:

However, the latest research shows that cells called “astrocytes” start to form new  nerve cells in the injured part of the brain following a stroke—the astrocytes eventually formed immature nerve cells, which then developed into mature nerve cells. So far, this process has only been mapped in mice, but it is still an amazing breakthrough.

”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”, says Zaal Kokaia, Professor of Experimental Medical Research at Lund University.

Perhaps most notably, the scientists identified the signaling mechanism that stops this conversion process from happening in an uninjured brain, which (down the road) could potentially allow us to start this regeneration and stop it when we choose. In a healthy brain, this signaling mechanism is active and inhibits the development of new nerve cells (in short, the regeneration process is turned off). But following a stroke, the signaling mechanism is suppressed and astrocytes can start the process of generating new cells. Zaal Kokaia notes what this means for the medical profession:

Interestingly, even when we blocked the signaling 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.

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.

”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”, says Olle Lindvall, Senior Professor of Neurology.

According to the American Stroke Association, in the United States alone, strokes impact some 795,000 people per year.

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