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Embryonic stem cell line found to be contaminated

The NIH Stem Cell Task Force chair said the discovery may lead to congressional hearings.

By Andis Robeznieks, amednews staff. Feb. 14, 2005.

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New calls for expanding the number of embryonic stem cell lines were sounded after University of California, San Diego, researchers identified an animal molecule that has contaminated one of the stem cell lines in the National Institutes of Health stem cell registry.

The contamination is believed to have occurred because the stem cell line in question was cultured using a layer of mouse cells. Since all the stem cell lines in the NIH registry have been grown using either mouse or fetal calf cells, they all are believed to be contaminated in the same way.

The UCSD researchers noted that many people have antibodies that attack the contaminating molecule -- N-glycolyneuraminic acid -- so any tissues developed using contaminated stem cells may result in a "deleterious immune reaction and/or rejection of the transplanted cells."

In the study, published online in the journal Nature Medicine on Jan. 23, researcher Ajit Varki, MD, and colleagues conclude that "it would be safest to start over again with newly derived [human embryonic stem cells] that have never been exposed to any animal products containing Neu5Gc and ideally, only ever exposed to serum from the intended transplant recipient. The current regulatory climate in the United States precludes this type of approach when using federal grant dollars."

Some critics of the Bush administration stem cell policy, which limits government funding for embryonic stem cells to existing lines, have taken this as a call to scrap the NIH registry and start all over, but Dr. Varki said that was not their intention.