(Time.com) -- Stems-cell research has joined global warming and evolution science as fields in which the very facts are put to a vote, a public spectacle in which data wrestle dogma.
Opponents of embryonic stem cell research -- starting with President Bush -- argue that you can't destroy life in order to save it; supporters argue that an eight-cell embryo doesn't count as a human life in the first place -- not when compared with the life it could help save.
Opponents say the promise of embryo research has been oversold; supporters retort that adult stem cells are still of limited use, and to fully realize their potential we would need to know more about how they operate -- which we can learn only from studying leftover fertility-clinic embryos that would otherwise be thrown away.
Back and forth it goes, the politics driving the science, the science pushing back.
Adult-stem-cell research is morally fine but clinically limiting, since only embryonic cells possess the power to replicate indefinitely and grow into any of more than 200 types of tissue.
Extracting knowledge from embryos that would otherwise be wasted is one thing, but scientists admit that moving forward will require a much larger supply of fresh, healthy embryos than fertility clinics could ever provide. And once you start asking people about creating embryos for the purpose of experimenting on them, the support starts to slow down.
Five years after Bush announced that federal money could go to researchers only working on embryonic stem cell lines that scientists had already developed, Democrats hope to leverage the issue as evidence that they represent the reality-based community, running against the theocrats.
States from Connecticut to California have tried to step in with enough funding to keep the labs going and slow the exodus of U.S. talent to countries like Singapore, Britain and Taiwan.
Meanwhile, private biotech firms and research universities with other sources of funding are free to create and destroy as many embryos as they like, because they operate outside the regulations that follow public funds.
For scientists who choose to work with the approved "presidential" lines, the funding comes wrapped in frustration. Today there are only 21 viable lines, which limits genetic diversity. They are old, so they don't grow very well, and were cultured using methods that are outdated. What's more, the chromosomes undergo subtle changes over time, compromising the cells' ability to remain "normal."
To get around political roadblocks, scientists are searching for a source of cells that is less ethically troublesome, ideally one that involves no embryo destruction at all.
One approach is "altered nuclear transfer," in which a gene would be removed before the cell is fused with the egg. That would ensure that the embryo lives only long enough to produce stem cells and then dies.
The most exciting new possibility doesn't go near embryos at all.
Dr. Shinya Yamanaka of Kyoto University reported tantalizing success in taking an adult skin cell, exposing it to four growth factors in a petri dish and transforming it into an embryo-like entity that could produce stem cells.
But even if scientists discover the ideal source of healthy cell lines, there is still much to learn about how to coax them into turning into the desired kind of tissue. And the closer scientists come to human trials, the more concerned the FDA will be with ensuring patient safety.
While scientists press ahead with embryo research, exciting news has come from the least controversial sources: the stem cells in umbilical-cord blood and placentas, and even in fully formed adult organs.
While not as flexible as embryonic cells, cord and placental cells have proved more valuable than scientists initially hoped. Although about 90% of cord-blood stem cells are precursors for blood and immune cells, the remaining 10% give rise to liver, heart-muscle and brain cells and more.
In the end, the source of the stem cells, whether embryonic or adult, doesn't matter to scientists. What counts is the ability to generate consistent, high-quality cells that can be safely transplanted.
Even the true believers among scientists, however, dispute eager politicians who have called for a Manhattan Project approach to research.
The key is to have the broadest cross section of scientists working across the field.
When it comes to such an impossibly complicated matter as stem cells, the best role for legislators and presidents may be neither to steer the science nor to stall it but to stand aside and let it breathe.
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