Canadian researchers have restored some movement in rats paralyzed from spinal cord injuries by using transplanted brain cells taken from adult mice.

Researchers led by Dr. Michael Fehlings, a neurosurgeon from the University of Toronto, said the experiment was encouraging. They predicted that one day brain cells could be taken from people with spinal cord injuries for their own treatment.

The scientists, from the Toronto Western Research Institute and the University of Toronto, wrote about their findings in Wednesday's issue of the Journal of Neuroscience.

The researchers crushed the spines of 97 rats and implanted stem cells derived from adult mouse brains into them. The mouse cells were labelled with a fluorescent marker so they could be traced after transplantation into the rats.

The transplants took place either two weeks or eight weeks after the injuries.

The rats treated after two weeks didn't regain the ability to walk normally, but did gain strength and co-ordination in their hind legs.

The rats treated eight weeks after the spinal cord injury were not helped by the treatment.

Previous studies showed improvements in animals with spinal cord injuries using transplanted cells. But experts said this experiment was interesting because it used stem cells from adult animals, rather than embryonic stem cells.

It's also notable because it showed an effect despite a two-week wait for treatment, said Dr. John McDonald, director of the International Center for Spinal Cord Injury at the Kennedy Kriger Institute in Balitmore, Md.

The cells used in the study are called neural precursor cells. While stem cells derived from embryos or fetuses can become any type of cell, neural precursor cells are limited in that they can only give rise to nerve cells, Fehlings said.

Neural precursor cells are found in the brain and in the spinal cord, Fehlings said, so researchers may one day be able to activate stem cells in the spines of injured patients without requiring a transplant.

Injured spinal cords lose the ability to regrow nerve fibres that have a sheath of myelin around them, like insulation around a wire.

More than one-third of the transplanted stem cells were able to restore the myelin sheath in the injured rats, easing their paralysis.