Tuesday October 17 03:08 AM EDT
By Nicolle Charbonneau
MONDAY, Oct. 16 (HealthScout) -- There's new hope for a potential treatment for the estimated 250,000 to 350,000 Americans with multiple sclerosis, a debilitating neurological disorder.
A study released today at the 125th annual meeting of the American Neurological Association describes a medical advance that may one day allow doctors to replace damaged nervous system cells in patients with multiple sclerosis, or MS.
MS is a chronic disease in which the body's immune system attacks the protective sheath, called myelin, which surrounds nerve cells throughout the nervous system. The scarring that results slows the passage of electrical impulses through the nerves, leading to weakness, numbness and vision problems, among other symptoms. In severe MS cases, paralysis may result.
The cause of MS isn't entirely clear, although theories suggest that viruses or genetics may be involved. There's no known cure, but drugs can manage the symptoms and even slow the return of relapses that affect some patients.
Myelin is part of cells called oligodendrocytes, and the new study replaced destroyed oligodendrocytes using neural stem cells. These "unspecialized" cells can be manipulated to develop into virtually any type of nervous system cell.
Lead author Dr. Seung Kim, of the University of British Columbia, had his first breakthrough when he was able to make human embryonic stem cells "immortal" -- capable of multiplying continuously -- in a petri dish.
Then, Kim and his team surgically implanted these human neural stem cells into the brains of "shiverer" mice with diseased myelin in their brains and spinal cords. The damaged myelin gave the mice the shivering gait and tremors characteristic of some MS patients.
Within two to five weeks of the surgeries, the previously damaged nerve cells grew new protective layers of myelin.
The study didn't specifically focus on the mice's symptoms. But researchers at Harvard have previously shown that shiverer mice receiving transplanted mouse neural stem cells had their tremors reduced.
Kim speculates that "human [cells] should do better in humans. That's our expectation."
Stephen Reingold, vice president of research at the National Multiple Sclerosis Society in New York City, believes stem-cell research like Kim's offers promise.
"The key problem in MS is an immunologic problem. What we really need to be able to do is to control the immune system damage to the cells in the brain that are responsible for MS. Once we have done that, the challenge is to regenerate new tissue," he says.
"At the moment, we don't have a way of effectively controlling immune damage in the brain, but [Kim's] is an appropriate strategy to be considering for the future, in terms of recovery."
Still, Reingold cautions, "this is work that is in progress."
One major hurdle for Kim's team to overcome is finding a new way to "immortalize" the embryonic neural stem cells. In the study released today, the team used an oncogene -- a cancer gene that makes cells multiply continuously. Obviously, this cancer gene could not be grafted into a human brain, meaning Kim will need to find another method of making neural stem cells "immortal." He anticipates he'll find a safer way to immortalize the cells in one to two years.
Kim and other researchers at the University of British Columbia are
already planning a study to transplant normal human oligodendrocytes into