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| Posted: October 8, 2007 |
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Dr. Irving Weissman, head of Stanford University's Institute for Stem Cell Biology, answered your questions on stem cell research in California in light of the state's $3 billion bond on the issue - funds which have sparked a research "gold rush" among stem cell scientists. |
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| John Ihnacik from St. Leonard, Md., asks: |
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| How are stem cells acquired? |
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| Dr. Irv Weissman responds: |
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Adult stem cells are taken from the tissue that holds them: Blood forming stem cells from bone marrow or mobilized blood or umbilical cord blood; all of these stem cells make blood and only blood. Another type of cell, called a mesenchymal cell (most workers think these are mesenchymal stem cells, but such cells are not totally purified yet) can be obtained from bone marrow or umbilical cord blood or, in fact, any tissue. These mesenchymal cells make fat, scar, and bone cells. Brain stem cells come from the brain. Muscle stem cells come from muscle. The acquisition and purification of each of these stem cells requires a concerted effort; blood-forming stem cells are only about 1 in 10,000 marrow cells. We think they must be pure for many applications. Embryonic stem (ES) cells come from pre-implantation blastocysts, as I described for Emily Schindler. These blastocysts cannot proceed in embryo development unless they land on and stick to the wall of the uterus. The most common method to make ES cells is to use an antibody that releases the inner cells from the outer ball layer, and then put them into test tubes with the right factors. |
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