Stem cells can repair damaged spinal tissue and help restore function in rats with spinal cord injuries, according to a new study. The findings may eventually lead to insights that result in new treatments for humans with spinal cord injuries.

Michael Fehlings, MD, PhD, and his colleagues at the Krembil Neuroscience Center at Toronto Western Research Institute and the University of Toronto also identified a critical window during which stem cell transplants may be effective, says the study, which appears in the March 29 issue of The Journal of Neuroscience.

"This work breaks new ground by showing that therapeutically useful stem cells can be derived from the adult brain of rodents, and that these cells can be caused to differentiate into the types of cells that are useful for repairing the damaged spinal cord," says Oswald Steward, PhD, director of the Reeve-Irvine Research Center for Spinal Cord Injury at the University of California, Irvine.

Fehlings' team used cells from the brains of adult mice labeled with a fluorescent marker, enabling them to trace the cells after they were transplanted into rats whose spines had been crushed. Stem cells transplanted up to two weeks after the initial injury survived thanks to a cocktail of growth factors and immune-suppressing drugs the team developed. More than one-third of the transplanted cells traveled along the spinal cord, were incorporated into damaged tissue, developed into the type of cell destroyed at the injured site, and produced myelin, an insulating layer around nerve fibers that transmits signals from the brain.

An injured spinal cord loses its ability to regenerate myelin-forming cells, leading to paralysis. Fehlings showed that where stem cells restored myelin in the injured spine, rats showed some recovery and walked with more coordination.

One new aspect demonstrated by the study is that "the maximal effect of transplanting these cells is early after injury," says New York University School of Medicine professor Moses Chao, PhD. "The timing of neural stem cell application therefore is critical to successful therapy in the injured spinal cord."

One focus of future research will be to determine the reason why stem cells transplanted weeks or months later fail to function or sometimes even survive.

Each year, some 11,000 Americans sustain spinal cord injury, most often in traffic accidents. Costs of the condition approach $10 billion per year.

The Journal of Neuroscience is published by the Society for Neuroscience, an organization of more than 37,500 basic scientists and clinicians who study the brain and nervous system.