Currently available lines of human embryonic
stem cells have been contaminated with a non-human molecule that
compromises their potential therapeutic use in human subjects,
according to research by investigators at the University of California,
San Diego (UCSD) School of Medicine and the Salk Institute in La Jolla,
California.
In a study published online January 23, 2005 in the journal Nature
Medicine, the researchers found that human embryonic stem cells,
including those currently approved for study under federal funding in
the U.S., contain a non-human, cell-surface sialic acid called
N-glycolylneuraminic acid (Neu5Gc), even though human cells are
genetically unable to make it. In a related paper published November
29, 2004 by the Journal of Biological Chemistry (JBC), the Varki group
has also discovered the exact cellular mechanism by which this occurs.
In
studies with one of the federally approved human embryonic stem cell
lines, the investigators determined that the Neu5Gc is incorporated by
the stem cells when they are grown or derived from laboratory cultures
that contain animal sources of the non-human Neu5Gc molecule. All
traditional culture-dish methods used to grow all human embryonic stem
cells include animal-derived materials, including connective tissue
cells (so-called "feeder layers") from mice and fetal calf serum.
"The human embryonic stem cells remained contaminated by Neu5Gc even
when grown in special culture conditions with commercially available
serum replacements, apparently because these are also derived from
animal products," said both papers' senior author Ajit Varki, M.D.,
UCSD professor of medicine and cellular & molecular medicine, and
co-director of the UCSD Glycobiology Research and Training Center.
The research in Nature Medicine was done with human embryonic stem
cells grown in the laboratory of Fred Gage, Ph.D., professor,
Laboratory of Genetics, the Salk Institute, La Jolla, California, an
adjunct professor of neuroscien
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Source:Eurekalert
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