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.

"Our findings demonstrate that cells that have never seen a brain can be developed into specific donor cells for nervous system repair," said Brüstle. Although the set of experiments did not show improved function as a result of the newly formed myelin, it is likely that repaired nerve fibers would conduct normally, said Ian Duncan a UW-Madison professor of neurology, a co-author of the Science paper and an authority on myelin deficiency diseases.

As a strategy for repairing damage by diseases such as multiple sclerosis, Duncan noted that 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 said.

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 dire genetic and acquired diseases, the best known being multiple sclerosis.

Importantly, in the study no teratomas -- tumors that frequently arise when undifferentiated stem cells are transplanted into animals -- were generated.

"In no instance did we see the formation of teratomas," said Duncan, "It strongly s
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Contact: Ian Duncan
duncani@svm.vetmed.wisc.edu
608-263-9828
University of Wisconsin-Madison
29-Jul-1999