Stem cells have helped heal long-term brain damage in radiation-affected rats.

A research paper published in the journal Cell Stem Cell describes how human stem cells were used to rebuild the insulation on the rats’ nerve cells, so they could carry messages once again.

“This technique, translated to humans, could be a major step forward for the treatment of radiation-induced brain … injury,” says Jonathan Glass, a neurologist at Emory University in Atlanta.

The researchers coaxed stem cells to become a particular type of brain cell that is destroyed by radiation, a common cancer treatment.

The ells were then grafted into the brains of irradiated rats, and within a few months, the test subjects’ performance on learning and memory tests improved.

“Radiation therapy … is very effective, but the problem is patients end up with severe disability,” Steve Goldman, a neurologist at the University of Rochester in New York, told reporters.

“Fuzzy thinking, a loss in higher intellectual functions, decreases in memory — all those are part and parcel of radiation therapy to the brain.” For children, the damage can be profound. “Those kids have really significant detriments in their adult IQs,” Goldman says.

Radiation destroys cells that would normally turn into oligodendrocytes - the type of cell that insulates the message-carrying part of nerve cells. To protective layer is known as a ‘myelin sheath’.

To restore the brain’s supply of oligodendrocytes, the team grew forerunners to the myelin-making cells from human stem cells.

They then injected the precursor cells into the brains of 18 rats that had received a regimen of multiple radiation doses, matching the levels that cancer patients receive.

After 10 weeks, the treated rats performed better on learning, memory and balance problems than the irradiated rats that had not received the new cells.

The treated rats were better at recognising when an object had been moved, or noticing an unfamiliar object. Rats with new cells in their cerebellum could trot on a rotating pole for a longer time without falling off than their untreated counterparts.

The data showed that most of the new cells survived, and were able to restore myelin to the denuded nerve cells.

The new cells did not spawn any tumours or morph into other types of cells, and the rats did not experience any side effects from the treatment.

The research team will now move on to studies with larger groups of rats, and use a radiation regimen that more closely matches human chemotherapy treatments.