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Six of One…

Induced pluripotent stem cells and embryonic stem cells are both important for research. Here’s how they compare.

By Rachael Moeller Gorman // Spring 2009
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When President George W. Bush banned federal funding for research on embryonic stem (ES) cell lines created after Aug. 9, 2001, stem cell research was significantly hampered. Of the 71 preexisting ES cell lines (genetically identical, immortal cultures of cells) for which Bush did permit funding, only 21 ended up being available to researchers (for example, some lines suffer when frozen for shipping). This is too few for a field that needs a wide array of genetically diverse material to support its mission to cure disease. Daunted, many researchers shied away from working with ES cells. Now that is likely to change, given President Barack Obama’s reversal of the ban. A higher number of healthy ES lines will allow better study of human development, but iPS cells will not fall by the wayside. Here’s why both types are important.


EMBRYONIC STEM (ES) CELLS

INDUCED PLURIPOTENT STEM (iPS) CELLS

POTENTIAL Replacing cells crippled or killed by disease, including heart disease, Alzheimer’s disease and type 2 diabetes Replacing cells crippled or killed by disease, including heart disease, Alzheimer’s disease and type 2 diabetes
SOURCE • Human embryos, especially embryos created during in vitro fertilization (IVF) that do not end up being implanted Adult cells, such as skin or the root of a hair
PROS
• Pluripotent (can become any cell in the body)
• Regenerate continuously (important because large numbers of cells are needed to replace diseased tissue)
• Considered the gold standard; have been studied eight years longer than iPS cells
• Pluripotent (can become any cell in the body)
• Regenerate continuously (important because large numbers of cells are needed to replace diseased tissue)
• Relatively easy to make
• Can be made genetically identical to the patient (sidestepping possible immune system attack)
CONS
• Unused IVF embryos are weaker than embryos that have been implanted, which could affect the viability of their cells
• Too few IVF embryos are available to supply the growing demand
• ES cells from IVF embryos would require immunosuppressive therapies so that the tissue wouldn’t be attacked by patients’ immune systems
• Clinical and scientific utility have yet to be fully confirmed
• Two of the four genes used to turn back the cells’ developmental clock might cause cancer, as might some of the viruses that carry the genes (though research is beginning to get around these problems)
• Low efficiency—for every iPS cell created from a skin cell, several thousands of other skin cells in the experiment remain unconverted
MORAL
OBJECTIONS
Human embryo destroyed while extracting the cells None
STATUS OF
CLINICAL
RESEARCH
Recent approval of a clinical trial to examine the safety of inserting ES cells into spinal cords of injured patients Researchers have treated disease in animals using iPS cells, but human trials are years away
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The Other Stem Cells

Konrad Hochedlinger

Once considered mere substitutes for embryonic cells, re-engineered adult cells are making breakthroughs of their own.

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