Nerve regrowth induced in damaged spinal cords

In a groundbreaking experiment, California scientists have used gene therapy to induce nerves to regrow in rats with damaged spinal cords, partially restoring their ability to walk.

Only two or three previous experiments have enabled animals with spinal cord injuries to regain some function, and the new experiment is the first to use gene therapy successfully to restore function.

There are no immediate plans to try the strategy in humans, said the researchers at the University of California in San Diego. But the results are another in a series of recent hopeful steps toward the goal of reversing paralysis from spinal cord injuries, which disable 10,000 or more people a year, most of them young and active.

The report published this week in the Journal of Neuroscience shows that a new biological tool, gene therapy, can be brought to bear on the problem, with encouraging results in experimental animals.

“I think it’s very exciting,” said Susan Howley, vice president for research of the American Paralysis Association, a nonprofit organization that promotes research on spinal injuries.

“Our report is yet another promising sign that experimental strategies can bring back some recovery of function in spinal cord injury,” said Dr. Mark H. Tuszynski, an associate professor of neuroscience at the university.

Last weekend, Florida researchers reported they had tried a different experiment in a disabled patient, implanting nerve cells from aborted fetuses into a patient’s damaged spinal cord. Howley pointed out that the gene therapy technique raises none of the ethical or legal quandaries raised by using fetal cells.

“In the long term, the use of fetal cells is not the happiest solution to the problem,” she said in an interview. “The hot things now are genetically engineered cells” taken from the individual’s own body and reprogrammed to deliver growth-enhancing substances to the damaged spinal cord, she said.

The strategy of converting normal body cells into miniature factories for growth factors was pioneered in the laboratory of Fred Gage of UCSD, a co-author of the new report. The greatest obstacle to repairing damaged spinal cord nerves is that they don’t heal or regrow following an injury, unlike nerves in the body’s extremities.

Until recently, scientists believed spinal cord nerves simply couldn’t regenerate, but they have now discovered that the spinal cord’s environment contains proteins that prevent unwanted growth of nerves as the body is “wired” in fetal development. Very recent research has demonstrated that if these inhibitory proteins are blocked, severed nerves can regrow, and that adding certain growth factors fosters that regeneration.