Study Results Are Setback to Bush’s Stem-Cell Policy ; Taint Found in All Human Embryonic Lines

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 the University of California at San Diego and the Salk Institute for Biological Studies in La Jolla, Calif., 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 a limited number of embryonic stem cell lines already in existence.

The scientists 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 was co- author of the paper in the current issue of Nature Medicine.

The researchers said the safest course is to create fresh batches of stem cells that are free of contamination from animal molecules – a process that could also take years.

That strategy would bolster the influence of the California Institute for Regenerative Medicine, a $3 billion funding agency established by voters last November specifically to circumvent the Bush restrictions.

“This is why [the ballot initiative] is so important,” said Susan Fisher, a professor of cell and tissue biology at the University of California at San Francisco who studies stem cells. “We will be able to do this basic research to be able to really produce a strong foundation on which this work can continue.”

When the Bush-approved stem cells were first isolated, they were grown in petri dishes lined with cells from mice and bathed in blood serum from calves and other animals. The animal material was used to encourage the stem cells to multiply while preserving their unusual ability to mature into any kind of human cell.

Researchers have suspected that exposing the stem cells to animal products could have contaminated them with viruses, proteins or other molecules that could be dangerous to people, and now they have evidence that it did.