McDonald is director of the spinal cord injury program and assistant professor of neurology and neurological surgery at the Washington University School of Medicine in St. Louis, Missouri. McDonald and his colleagues implanted stem cells that had been primed to become neural cells in rats and mice that lacked myelin, the tissue that insulates the nervous system.
Stem cells are among the first cells to form in animals and humans after the fertilization process.
The central nervous system is much like the power lines that bring electricity into our homes, McDonald says. Researchers found that the implanted stem cells grew to form myelin, and covered both the injured spinal cords in rats and the naturally myelin-deficient spinal cords of a certain kind of mouse. People with spinal cord injuries or multiple sclerosis may benefit from stem-cell therapy since the replacement of myelin can help the body send messages along the nervous system more effectively. For instance, McDonald says, a person may be able to strengthen the use of a hand or have better bladder control than they did before the myelin was replaced. There are some moral questions that have accompanied the use and study of stem cells, since stem cells can come from human embryos.