Immune Cells

Converting Immune Cells in the Brain Can Aid in Post-Stroke Recovery


A recent study conducted by researchers at Kyushu University in Japan has shown promising results in converting brain immune cells into neurons. The conversion of these cells replaces damaged neurons and restores motor function in mice affected by strokes. The findings offer potential for the development of a treatment for stroke in humans.

When an individual experiences a stroke or other cerebrovascular disease, the brain is deprived of blood flow, causing damage or death to neurons. This results in various physical and mental deficits. The team of researchers aimed to find a way to replace these lost neurons by converting microglia, the brain’s primary immune cells, into neurons.

Lead author of the study, Takashi Irie, noted that whereas skin and bone cells can replicate to heal the body, neurons in the brain do not possess the same regenerative ability. This leads to permanent damage in most cases. Hence, the team sought a method to substitute lost neurons.

Based on their previous research, the researchers discovered that microglia could be induced to develop into neurons in healthy mice. After a stroke, microglia migrate to the site of the injury and rapidly replicate to remove damaged or dead brain cells.

Microglia are abundant and conveniently located in the area where they are needed, making them ideal for conversion, according to Irie.

To test their hypothesis, the researchers induced a stroke in mice by temporarily blocking the right middle cerebral artery, a major blood vessel associated with strokes in humans. After a week, the mice exhibited motor function difficulties and a significant loss of neurons in the striatum, a brain region responsible for decision-making, action planning, and motor control.

Using a lentivirus, the researchers inserted DNA into microglial cells at the site of the stroke injury. This DNA contained instructions for producing NeuroD1, a protein that induces neuronal conversion. Over the following weeks, the cells developed into neurons.

After three weeks, the mice showed improved motor function. By the eighth week, the newly induced neurons had successfully integrated into the brain’s circuitry. When the researchers removed the new neurons, the motor function improvements were lost, confirming that the new neurons directly contributed to the mice’s recovery.

Senior author of the study, Kinichi Nakashima, expressed optimism about the results, stating that the next step would involve testing whether NeuroD1 is also effective in converting human microglia into neurons. Furthermore, they aim to confirm the safety of their gene insertion method in microglial cells.

Since the treatment was administered during the acute phase following a stroke, when microglia have migrated to the injury site, the researchers plan to investigate whether similar recovery can be achieved at later stages in mice. This would provide valuable information about the potential of this method in treating stroke in humans.

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