The stem cells developed into the type of tissue that was destroyed at the injured area and were able to produce myelin -- an insulating layer around nerve fibers that transmits signals from the brain.

The team said the technique appeared to work best in the two weeks after the spinal cord was injured.

Hope for Treating Disabilities, Alzheimer's

It has long been hoped that stem cells could hold the key to treating severe disability as well as serious illnesses such as Alzheimer's disease.

In the latest research, Dr. Michael Fehlings and colleagues from the University of Toronto took stem cells from the brains of rodents.

These cells were labeled with a fluorescent marker, allowing the scientists to trace the cells after they were transplanted into the rats' crushed spines.

Using a cocktail of growth factors and immune-supressing drugs, the stem cells transplanted up to weeks after the initial injury survived in the spine.

The scientists found that more than one-third of the transplanted cells traveled along the spinal cord and were incorporated into the damaged tissue.

Rats Showed Some Recovery

These cells developed into the type of tissue that was destroyed at the injured area and were able to produce myelin -- an insulating layer around nerve fibers that transmits signals from the brain.

When the spinal cord is injured, it loses the ability to regenerate myelin-forming cells, which leads to paralysis.

Dr. Fehlings found that where the stem cells restored myelin in the injured spine, the rats showed some recovery and were able to walk with more coordination.

Dr. Oswald Steward, director of the Reeve-Irvine Research Center for Spinal Cord Injury at the University of California, welcomed the study. "These cells can be caused to differentiate into the types of cells that are useful for repairing the damaged spinal cord," he said.