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Tracy Hampton, PhD

JAMA. 2005;293:789.

	Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

While many scientists have been searching for medical breakthroughs with human embryonic stem cell (HESC) lines approved for study under federal funding in the United States, research published in the January 23 online issue of Nature Medicine (http://www.nature.com/naturemedicine/) revealed that these cells may be unsuitable for therapeutic use in humans. Findings by investigators at the University of California, San Diego, and the Salk Institute in La Jolla, Calif, could cast a shadow over many research endeavors across the country.

It is standard practice to culture HESCs with animal-derived materials, including connective tissue cells (called feeder layers) from mice and fetal calf serum. Unfortunately, the practice contaminates the HESCs with the nonhuman, cell surface sialic acid called N-glycolylneuraminic acid (Neu5Gc), the study showed. The investigators detected the presence of Neu5Gc on the cell surfaces of HESCs through the use of probes and a technique called . . . [Full Text of this Article]