By Merritt McKinney

NEW YORK (Reuters Health) - In an experimental procedure that holds promise as a treatment for multiple sclerosis (MS) and other diseases that ravage the central nervous system, researchers have transplanted nerve cells into the brain of a woman with MS.

The degenerative neurological disease MS is one of 30 to 40 diseases that destroy myelin, the insulation that covers nerve fibers, according to the principal investigator of the experimental treatment, Dr. Timothy Vollmer of Yale University School of Medicine in New Haven, Connecticut. Without the protective sheath of myelin, nerve fibers have a hard time communicating, he told Reuters Health in an interview.

"The fibers tend to short out electrically," he explained. "That's what causes the disabilities."

MS destroys cells called oligodendrocytes, which produce the myelin that covers nerve fibers in the brain and spinal cord. But the myelin that protects peripheral nerves, which are found in other parts of the body, is produced by cells called Schwann cells, which elude the attack of MS. In animal studies, Schwann cells have been able to fill in for destroyed oligodendrocytes to produce myelin for the brain and spinal cord.

Last week, Vollmer and his colleagues tested the approach in a woman with MS. On July 17 they removed a nerve from the patient's ankle. The next day, after isolating Schwann cells from the nerve, they injected the cells into the woman's brain in a technique called stereotactic surgery.

After spending a day in the intensive care unit for observation, the woman is doing well and should be going home from the hospital soon, Vollmer said.

It will be a while, however, before the researchers will know whether the transplant was a success, according to Vollmer.

"We'll prove that by studying the patient very carefully," he said.

Six months from now the researchers will use MRI scans to look for signs that the Schwann cells have survived and grown to produce myelin. In case the growth is not extensive enough to show up on the MRI, however, Vollmer's team will take a small biopsy from the brain to see whether the cells have survived and produced myelin.

Even if the transplant proves to be successful, "it's not likely to result in major improvement in the patient's function," Vollmer noted. He explained that Schwann cells were transplanted to a site of MS damage, or lesion, in the brain that is not the major source of symptoms. Because the goal of this phase of the study is to make sure that the procedure is safe and to determine whether transplanted cells can survive, Vollmer and his colleagues chose the "safest" area of the brain.

If the procedure does pass the first round of tests in this patient and a handful of others, Vollmer said the team hopes to transplant the cells into the types of brain lesions that cause most of the disability in MS patients. Eventually, they may try to transplant other types of myelin-growing cells to see whether they improve symptoms in MS and other myelin destroying diseases, Vollmer said.

"We're obviously very cautious, but we're trying to lay a very strong scientific foundation," the researcher said.