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Facts in QuoteEmbryonic Stem Cell Research: A Reality CheckMarch 2002 |
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Embryonic stem cell research is often hailed as having brought us to the brink of curing numerous diseases, including Alzheimer's, Parkinson's, diabetes, spinal cord injury and diseases of the heart. But despite the extravagant claims, there are numerous obstacles to therapeutic use of human embryonic stem cells, whether they are derived from frozen embryos, or from cloned human embryos. hese very real drawbacks rarely receive the same public attention as the purely speculative claims regarding the potential benefits. As John Chute, then head of the Hematopoietic Stem Cell Studies Section at the Naval Medical Research Center, testified before Congress in September 2001: "These limitations of embryonic stem cells as a source of tissue for human transplantation should be openly and honestly presented to the public, since treatments and cures from these cells are not imminent." And the New York Times has reported that cures from human embryonic stem cells "if it ever happens, it will not happen soon… although they worked with mouse embryonic stem cells for 20 years and made some progress, researchers have not used these cells to cure a single mouse of disease," ("A Thick Line Between Theory and Therapy, as Shown with Mice," 12/18/01). In fact, problems associated with embryonic stem cells include: Difficulty in Establishing and Maintaining Embryonic Stem Cell Lines"‘Simply keeping human embryonic stem cells alive can be a challenge,' says Peter Andrews of the University of Sheffield in England. For more than a year, he and his colleagues have been experimenting with embryonic stem cell lines that James Thomson derived at the University of Wisconsin, Madison. ‘They're tricky,' Andrews says. It took several false starts--and a trip to Wisconsin --before the researchers learned how to keep the cells thriving, he says. [Harvard's Douglas] Melton uses almost the same words: Human embryonic stem cells ‘are trickier than mouse,' he says. ‘They're more tedious to grow.'" --"Stem cells: New excitement, persistent questions," Science 290, 1672-1674; 12/1/00 "Only one [embryonic stem cell line] works well," he said. "The others, they have all kinds of different problems. They either don't grow well or they differentiate spontaneously, kind of like popcorn popping before you've added heat…In my view [human embryonic stem cells'] properties will degrade with time. Everyone is fearful that the more you grow them in the dish, the more they lose their properties." --Doug Melton, Harvard University researcher, quoted in the "Stem Cell Decision Examined," the Washington Post, 8/12/01 "[T]he poor availability of human oocytes, the low efficiency of the nuclear transfer procedure, and the long population-doubling time of human ES cells make it difficult to envision this [embryo cloning to produce stem cells] becoming a routine clinical procedure…" --J.S. Odorico, D.S. Kaufman, J.A. Thomson, "Multilineage differentiation from human embryonic stem cell lines," Stem Cells 19, 193-204; 2001 "…[T]he use of such therapeutic cloning to produce useful treatments may simply be impractical… ‘It's too laborious and costly to employ as a routine therapeutic procedure,' said Dr. Alan Colman, research director at PPL Therapeutics, the Scottish company that helped clone Dolly the sheep…For one thing, unless success rates improve dramatically, the therapeutic cloning will require a large number of eggs—and women willing to donate them-- to make clones for the thousands or even millions of potential patients. ‘They're never going to have enough women's eggs available to do it,' said Dr. Alan Trounson, director of the Monash Institute of Reproduction and Development in Australia and an adviser to ES Cell International, a company based in Singapore and Australia." --"Using Cloning to Tailor Treatment Has Big Hurdles, Including Cost," New York Times, 12/18/01 Difficulty in Obtaining Pure Cultures in the Dish"And so far reports of pure cell populations derived from either human or mouse ES cells are few and far between--fewer than those from adult cells." "Can Adult Stem Cells Suffice?," Science, 292, 1820-1822, June 8, 2001 "Rarely have specific growth factors or culture conditions led to establishment of cultures containing a single cell type." --J.S. Odorico, D.S. Kaufman, J.A. Thomson, "Multilineage differentiation from human embryonic stem cell lines," Stem Cells 19, 193-204; 2001 "The work suggests that it will not be simple to produce the pure populations of certain cell types that would be required for safe and reliable cell therapies—much less the hoped-for replacement organs, says stem cell researcher Oliver Brüstle of the University of Bonn in Germany…Says Brüstle: ‘At present, it looks like it is really difficult to differentiate these [human] cells into more advanced cell types.' [Harvard University researcher Douglas] Melton agrees. ‘It's unlikely anyone will ever find a single growth factor to make a dopaminergic neuron,' as some might have hoped, but the work provides ‘a starting place,' he says." --"Stem cells: New excitement, persistent questions"; Science 290, 1672-1674; 12/1/00 "One problem is simply to find a way to get stem cells to grow into the types of cells that are needed, and not a mixture of cells. Scientists know this is a thorny problem, but their views were not widely heard when the public and politicians seemed to assume that it was easy to grow any kind of tissue desired from embryonic stem cells. In fact, no one has been able to do this even with mouse cells. Using stem cells to cure diabetes, for example, would mean converting them to islet cells…The science is not even close…The task of getting stem cells to develop into specialized nerve cells and then getting those cells to repair the damage in the disease is well beyond today's science, experts say."
--"A Thick Line Between Theory and Therapy, as Shown with Mice,"
New York Times, 12/18/01 "[T]he possibility arises that transplantation of differentiated human ES cell derivatives into human recipients may result in the formation of ES cell-derived tumors." --J.S. Odorico, D.S. Kaufman, J.A. Thomson, "Multilineage differentiation from human embryonic stem cell lines," Stem Cells 19, 193-204; 2001 "But ES cells have plenty of limitations, too. For one, murine ES cells have a disturbing ability to form tumors, and researchers aren't yet sure how to counteract that." --"Can Adult Stem Cells Suffice?," Science, 292, 1820-1822, 6/8/01 What's more, new research suggests that embryonic stem cells may be a little too plastic. ‘The emerging truth in the lab is that pluripotent [embryonic] stem cells are hard to reign in,' University of Pennsylvania bioethicist Glenn McGee told MIT's Technology Review. ‘The potential that they would explode into a cancerous mass after a stem cell transplant might turn out to be the Pandora's box of stem cell research.'" --"Stemming the Tide: Hard Cell," The Wall Street Journal Europe, 8/3/01 Genomic Instability"The epigenetic [gene expression] state of the ES cell genome was found to be extremely unstable." "These data imply that even apparently normal cloned animals may have subtle abnormalities in gene expression." --D. Humphreys et al.; "Epigenetic instability in ES cells and cloned mice," Science 293, 95-97; July 6, 2001 |
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