WASHINGTON (AP) — Researchers have shown that master cells from rodent embryos can be used to repair nerves in the spinal cord and brain, a step toward new treatment for nerve disorders such as Parkinson's disease and multiple sclerosis.
In laboratory studies, researchers guided the evolution of embryonic stem cells from mice into mature nerve cells that were transplanted into rats where they produced a nerve insulating material that the rats lacked.
"We have shown that you can make olgiodendrocytes and astrocytes (two types of nerve cells) from embryonic stem cells", said Dr. Ronald D.G. McKay, a molecular biologist at the National Institutes of Health. "This approach could be used for a number of diseases," including Parkinson's and multiple sclerosis.
McKay is a co-author of a study appearing Friday in the journal Science.
In the study, the olgiodendrocytes and astrocytes grown from stem cells were put into rats with a genetic disease that blocks formation of the nerve insulating material called myelin. The rats' disorder is the rodent equivalent of a human myelin disorder called Pelizaeus- Merzbacher disease.
The researchers found that the transplanted cells caused myelin to grow around the nerve fibers in the rats. McKay said that by starting with mouse embryonic stem cells, researchers had a biological marker that enabled them to prove that the new myelin growth in the rats originated from the transplanted mouse cells.
The loss of myelin is a key part of several neurological diseases, particular multiple sclerosis. In MS, the body attacks and destroys myelin, causing a crippling loss of nerve function.
"A considerable amount of science has to be generated before it can be used in humans with multiple sclerosis, but this holds great promise," said Dr. Ian D. Duncan of the University of Wisconsin, a co-author of the study.
Stephen Reingold, a vice president for science at the National Multiple Sclerosis Society, said the study is "intriguing and exciting" because it showed stem cells could be used to grow new myelin. But he cautioned that the myelin disorder in the rats is different from multiple sclerosis.
"We have to keep the perspective that these are not human cells they are playing with," Reingold said. "One can hope that a similar (technique) will be applicable to human stem cells", but that has yet to be proved, he said.
Reingold also said that even though the researchers showed that the transplanted cells grew new myelin, it is not clear if this improved the function of the nerves themselves.
McKay said the most important element of the study is that it advances the fundamental understanding of how to cause embryonic stem cells to mature into specific types of cells that may then be useful in treating patients.
"We have shown that you can take embryonic stem cells and make them brain stem cells and that it is really quite simple," he said.
Embryonic stem cells arise early after conception and are the ancestral cells for all of the body's tissue, such as muscle, bone, nerves, skin and blood. Experts believe if researchers can learn how to direct stem cells to make specific types of cells then it may be possible to replace diseased tissue with new growth.
In the new study, McKay and his colleagues demonstrated they can direct the stem cells to grow specific types of nerve cells and that these cells, in turn, will grow new nerve tissue when they are transplanted into rats.
"This is the first study showing that embryonic stem cells can be used for brain and spinal cord repair in an animal model of a human neurological disease," Dr. Oliver Brustle, a University of Bonn researcher and first author of the paper, said in a statement.
"The next trick," said Duncan, "will be to get human embryonic stem cells to do the same thing. If they do, then potentially those cells could be use for grafting into patients with myelin disease" such as MS.
The use of human embryonic stem cells remains an unresolved ethical controversy. For now, federal funding of human embryo research is forbidden by law.
Privately funded researchers have grown a cell line that originated from human embryos and have made such cells and have made them available to other researchers.
Dr. Harold Varmus, head of the National Institutes of Health, has announced
that he believes these cells can be used in federal research. Varmus has
been supported by the Clinton Administration, but many in Congress oppose
human embryo research.