Breakthrough Immune Cell Transformation Restores Brain Function After Stroke

A new treatment may be in sight for stroke patients after scientists successfully reprogrammed immune cells to replace damaged brain cells and restore brain function after stroke-like injury.

Every year, more than 795,000 people in the U.S. have a stroke, the Centers for Disease Control and Prevention estimates. Strokes occur when blood vessels in the brain become blocked, narrowed or burst and can often result in serious brain damage. This can result in reduced mobility for more than half of stroke survivors aged over 65, and it can cause permanent memory loss, cognitive impairment, and mood disorders among other complications.

"Currently, there is no effective treatment for stroke patients to restore neurological function," Taito Matsuda, assistant professor in the department of stem cell biology and medicine at Kyushu University in Japan, told Newsweek.

Unlike most cells in our bodies, brain cells cannot easily be regenerated and so any damage to the brain is often permanent. However, in a recent study, published in the Proceedings of the National Academy of Sciences, Matsuda and colleagues may have found a solution for replacing these lost neurons.

Our brains have two main types of brain cells: neurons, which act like the wires of the brain; and glial cells, which act like electricians, maintaining and protecting the neurons. Among these glial cells are the microglia, immune cells that are specialized to defend the brain from infections and damage. Using cutting-edge biotechnology, the team was able to turn these microglial cells into neurons.

"Microglia are abundant and exactly in the place we need them, so they are an ideal target for conversion," Takashi Irie, first author of the study, said in a statement.

After inducing stroke-like injuries in a group of mice, the team was able to reprogram a subset of the mice's microglial cells to express the specific genes required to perform neuronal activities. This involved turning on a molecular switch, called NeuroD1, which activates neuronal genes and induces neuronal conversion in situ. In other words, the cells can be transformed from inside the brain.

"I was very surprised because normally these cells do not differentiate into neurons," Matsuda said. "It was also an incredible result for other researchers, so we conducted many experiments to prove this conversion."

After between four to eight weeks, these new brain cells had successfully integrated into the mice's brains, and after just three weeks, the mice showed improved motor function in behavioral tests. "If this technology can be used to generate new neurons in a patient's brain, lost neurological function can be restored," Matsuda said.

Of course, the human brain is quite different from that of a mouse, so further work needs to be done to confirm its applicability to human stroke patients.

"It will take some time before it can be applied to humans, as it needs to be tested to see if it works in non-human primates and whether human microglia can be converted to neurons," Matsuda said.

However, these results are still very promising and offer a promising solution to stroke-related brain injury in the future.