Using stem cells grown in the laboratory, a team of scientists from the University of Bonn (Germany) Medical Center, the National Institute of Neurological Disorders and Stroke, and the University of Wisconsin-Madison have successfully transplanted those cells into the nervous systems of ailing rats and arrested the course of a debilitating congenital disease. Although years from clinical application, the work is important because it shows that cells grown from scratch can be used to repair defective nerves.
The work was accomplished using embryonic stem cells that arise within days of conception in a fertilized egg and very quickly develop into all the different kinds of cells--blood, bone, muscle, neurons--that make up the body. Such cells hold an enormous therapeutic potential through the promise of unlimited supplies of laboratory-grown replacement tissue to treat many congenital and acquired illnesses, including heart disease, neurological disorders such as Parkinson's disease or multiple sclerosis, and diabetes.
In the study, stem cells were coaxed down a developmental pathway to become oligodendrocytes and astrocytes, key cells of the central nervous system. Transplanted into the spinal cords of fetal and newborn rats that lack myelin, a tissue that covers some nerve fibers, the cells were observed to promote the growth of the myelin sheaths essential to the ability of nerves to conduct electrical impulses and function normally. Myelin is a critical insulator, helping nerve fibers conduct the electrical impulses that drive ambulation, speech, sight, and hearing. Without it, fibers conduct slowly or not at all. The absence of myelin is a manifestation of an array of genetic and acquired diseases, the best known being multiple sclerosis.
Two weeks after being surgically transplanted into either fetal or newborn rats with a congenital disease identical to the rare human myelin disorder Pelizaeus-Merzbacher disease, the laboratory-grown cells had developed into numerous myelin sheaths around nerve fibers previously without myelin. When the cells were transplanted into the fetal brain, they were later found to have spread widely.
Although the experiments did not show improved function as a result of the newly formed myelin, it is likely that repaired nerve fibers would conduct normally, indicates lan Duncan, professor of neurology, University of Wisconsin. As a strategy for repairing damage by diseases such as multiple sclerosis, this approach focuses on replacing lost myelin, not stopping ongoing disease, something that will require additional medical therapy. "Nonetheless, we believe eventually it will have clinical applications," he predicts.
COPYRIGHT 2000 Society for the Advancement of Education
COPYRIGHT 2000 Gale Group
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