( ces at UCSD and an author on the Natur...)Current human embryonic stem cell lines contaminated UCSD/Salk team finds

ces at UCSD, and an author on the Nature Medicine paper. Previously, the Varki lab found in 1998 that humans are uniquely different from other mammals studied in that people do not express Neu5Gc*. In a 2003 study**, the UCSD researchers found that humans have naturally occurring antibodies that are directed against Neu5Gc. In the current Nature Medicine paper, the scientists found that the human embryonic stem cells contaminated with Neu5Gc became, effectively, like animal cells, being attacked by human antibodies, and thus rendering them useless as a potential therapeutic tool in humans. "It's an important safety issue because this opens up the idea that metabolic transfer of glycans is occurring between cells," said Gage. "Also, components of the growth medium have the capacity to change the immunological characteristics of the human ES cells. More research is needed to understand the optimal conditions for preparing human cells for therapeutic application." "We considered that one partial solution to the problem was to use human serum in the growth medium," Varki said. When the team grew the cells in heat-inactivated human serum specially selected for low concentrations of anti-Neu5Gc antibodies, the immune response was significantly reduced, but not completely eliminated. In their experiments, the researchers used recently developed probes to detect the presence of Neu5Gc on the cell surface of human embryonic stem cells that had been grown in traditional culture conditions. The scientists further confirmed the presence of Neu5Gc with a process called electrospray mass spectrometry. The percentage of total sialic acids present as Neu5Gc in the embryonic stem cells varied from 2.5 to 10.5 percent. In human embryonic stem cells that had been allowed to differentiate into embryoid bodies (EB), which is the first step in preparing them for potential use in humans, the percentage of total sialic acids present still ranged from 5 to 17 percent. Varki and his team not
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Source:Eurekalert


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