Scientists eased the paralysis of rats with spinal cord injury by transplanting cells taken from the brains of adult mice, an encouraging sign for developing a human treatment, researchers reported.

Someday, such cells might be taken from the brains of patients with spinal cord injuries for their own treatment, said researcher Dr. Michael Fehlings.

In addition, similar cells are found in the spinal cord, so perhaps researchers may find a way to activate them to improve a person's mobility, he said.

Fehlings, of the University of Toronto and the Toronto Western Research Institute in Canada, and colleagues report the rodent experiment in Wednesday's issue of the Journal of Neuroscience.

The work used 97 rats. Spinal injuries were created in the lab, and the mouse brain cells were implanted two weeks or eight weeks later. While the animals didn't start walking normally, those treated at the two-week mark did gain in coordination and ability to bear weight on their hind limbs.

Those treated eight weeks after the injury weren't helped, which Fehlings and other experts said illustrated a hurdle in treating spinal cord patients long after their injury.

Previous studies also have reported improvement in paralyzed lab animals with transplanted cells. But experts said the new work was notable because the cells were taken from adult animals rather than fetuses or embryos, and they produced an effect even when implanted two weeks after the injury.

"It's an important step forward," said Dr. John McDonald, director of the International Center for Spinal Cord Injury at the Kennedy Krieger Institute in Baltimore.

The transplanted cells, called neural precursor cells, are not as versatile as embryonic stem cells because they can give rise only to cells of the nervous system, Fehlings said.

Once implanted, they formed cells that can create a sheath around nerve fibers that resembles insulation around wires. Such sheaths are disrupted in spinal cord injury and restoring them produced the therapeutic effect in the rats, he said.