All human embryonic stem cell lines approved for use in federally funded research are contaminated with a foreign molecule from mice that may make them risky for use in medical therapies, according to a study released Sunday.
Researchers at UC San Diego and the Salk Institute for Biological Studies in La Jolla report that if the stem cells are transplanted into people, the cells could provoke an immune system attack that would wipe out their ability to deliver cures for diseases such as Parkinson's, Alzheimer's and diabetes.
The finding is a setback to the Bush administration's controversial policy that provides federal funding only for research using embryonic stem cell lines that were created before August 2001. Evidence that all such lines are contaminated supports long-standing concerns among researchers that the lines eligible for federal money are insufficient to propel research forward.
The scientists who wrote the study say it could take at least a year or two -- if it is possible at all -- to find a way to salvage the stem cells by wiping them clean of the mouse molecules.
"We don't know, but I'm trying to be optimistic," said Fred H. Gage, a professor of genetics at the Salk Institute who co-wrote the paper in the current issue of Nature Medicine.
The researchers said the safest course was to create fresh batches of stem cells that were free of contamination from animal molecules -- a process that could also take years.
The need to develop new, uncontaminated embryonic stem cell lines would bolster the influence of the California Institute for Regenerative Medicine, a $3-billion funding agency established by state voters in November to circumvent President Bush's restrictions.
"This is why Prop. 71 is so important," Susan Fisher, a UC San Francisco professor of cell and tissue biology, said of California's stem cell research measure. "We will be able to do this basic research to be able to really produce a strong foundation on which this work can continue."
The new state agency allows the creation of new stem cell lines and will fund about $300 million a year in embryonic stem cell research for the next decade -- more than 10 times the yearly spending at the federal level. The initiative marks the largest state investment in basic scientific research, an area traditionally funded by the National Institutes of Health.
