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Pastimes : Let's Talk About Our Feelings!!! -- Ignore unavailable to you. Want to Upgrade?

To: cosmicforce who wrote (94987)	1/27/2005 10:03:12 PM
From: Grainne	Respond to of 108807

I read earlier this week that all of Bush's approved stem cell lines are compromised with cow and mouse cells, and that this makes them unusable because humans produce antibodies. You have probably read this article as well, but I'll post it because I think it's interesting. I do have a question--when we eat red meat and milk and our bodies form antibodies, does that cause any potential harm to us or anything? US stem cells tainted by mouse material 14:25 01 November 2004 NewScientist.com news service Fred Gage, Salk Institute Ajit Varki, UCSD Carol Ware, University of Washington International Society for Stem Cell Research The stem cell lines available for federally-funded research in the US have characteristics which mean they may never be used for medical treatments in humans, a new study suggests. Fred Gage at the Salk Institute in La Jolla, California and Ajit Varki at the University of California, San Diego, US, have shown that human embryonic stem cells (hESC) cultivated on a scaffolding of mouse “feeder” cells take on the properties of the rodent cells. Consequently, if implanted in a human they would provoke an immune response that would kill the hESCs, they say. The finding reinforces calls by US stem cell researchers for their government to free up federal money to research fresh lines of human ESCs, grown on non-biological scaffolds. Stem cell research in the US is currently limited to 22 lines, following a policy introduced by President George W Bush in 2001. These lines were derived before August 2001 and all of the cells were grown on a scaffolding of mouse cells. “It’s a new twist on why it can’t be done,” says Richard Hynes, a biologist at the Massachusetts Institute of Technology and a member of the National Academy of Sciences’ committee on guidelines for human embryonic stem cell research. Red meat ESCs are primitive, unspecialised cells which have the potential to develop into any cell in the body – so they could theoretically be used to replace damaged cells and tissues. In 1998, Varki showed that a sugar present on the surface of most mammal and rodent cells is lacking in humans. Called N-glycolyl-neuraminic acid, or Neu5Gc, it differs from a sugar humans do express, N-acetyl neuraminic acid, or Neu5Ac by a single oxygen atom. In 2003 he showed that humans absorb Neu5Gc molecules when they eat red meat and milk products and have consequently developed antibodies against it. Varki also found that human cells in culture absorb Neu5Gc from any surrounding sources and incorporate it into their own cell surfaces. Now Varki and Gage have added human blood serum to samples of cells derived from the 22 approved lines and shown that the hESCs trigger an immune response which kills them. “When they are transplanted into the body these cells are perceived as being animal cells,” Gage told a meeting at the National Academies of Science on 12 October, 2004. The details of the work are to be published later in 2004. Jelly-like matrix “It’s always been known that these would not be ideal candidates for clinical trials,” says Evan Snyder, director of the Stem Cell and Regeneration Program at the Burnham Institute in La Jolla. But up until now the main fear was that pathogens from the mouse could pass to humans. “I don’t think anybody is even thinking of putting these cells into people,” adds Hynes. So privately-funded US scientists are actively searching for non-biological alternatives to the mouse cell scaffolding. Contenders include a jelly-like matrix, and human muscle or blood cells. But because Bush-approved research is limited to the older lines, federally-funded scientists cannot take advantage of newer stem cells grown on alternative scaffoldings. This “significantly” limits the value of the federally-funded research, says Snyder. “It renders [the government-approved cells] incredibly suspect. All work should be done with fresh lines,” he says. A second unpublished study by Carol Ware at the University of Washington, Seattle, US, also revealed that cells derived from five of the 22 lines were so difficult to grow and separate that they may not be clinically useful. newscientist.com