Scientists Make Stem Cells; No Harm to Embryos
By RICK WEISS
WASHINGTON – Two teams of scientists provided the first definitive evidence Sunday that embryonic stem cells can be grown in laboratory dishes without harming healthy embryos, an advance that some scientists and philosophers believe could make the medically promising field more politically and ethically acceptable.
The work, done with mouse cells, generated several colonies of mouse embryonic stem cells without destroying any embryos that otherwise could have developed into mice.
If the new approaches were to work with human cells, as many scientists suspect, they could help defuse a moral maelstrom that has raged since human embryonic stem cells were discovered seven years ago. But the new techniques raise ethical issues of their own.
Stem cells from days-old human embryos can morph into virtually every kind of tissue, including nerves to replace those destroyed by spinal injuries and cardiac muscle to fill in for cells lost in a heart attack. Scientists see stem cells as the key to a new era of regenerative medicine.
Until now, however, the only way to get these cells was to destroy young embryos – which, though smaller than the period at the end of this sentence, are deemed by some people as “the youngest members of the human family” and deserving of certain human rights.
The new work suggests an alternative might be possible.
“This establishes the scientific feasibility of the idea that you can obtain fully functional embryonic stem cells from an entity that is not a natural, normal embryo,” said William B. Hurlbut, a Stanford University professor and member of President Bush’s Council on Bioethics.
But few scientists, ethicists or others, it turns out, are convinced the new methods transcend the problems inherent in traditional stem cell approaches. Many say the new work only reveals how intractable the problem remains and how unlikely it is that science will resolve what is essentially a matter of spiritual belief.
That is because one of the new methods still subjects a human embryo to a small added risk, and, even more controversially, the other approach involves deliberately creating an embryo with a disabled version of a gene that is crucial to normal development.
Although some people condone experiments on such gene-altered embryos because they have no potential to grow into babies, others see the work as the purposeful creation of fatally hobbled beings to use as research subjects.
“The concern is that an embryo is being generated that is doomed to die very soon,” said Markus Grompe, a geneticist who runs the stem cell program at Oregon Health & Science University in Portland.
Alexander Meissner and Rudolf Jaenisch of the Whitehead Institute for Biomedical Research in Cambridge, Mass., created those altered embryos by first disabling a gene called Cdx2 in a skin cell taken from a mouse. That gene is not normally active in skin, but during early embryo development it governs the creation of the placenta, which allows a developing fetus to feed and survive in the womb.
As described in Sunday’s online issue of the journal Nature, the team fused that cell with a mouse egg whose own genetic material had been removed – a now-commonplace cloning procedure that leads to the growth of an embryo in a lab dish. In this case, though, with every new cell in the growing embryo lacking Cdx2, the embryo had no hope of growing a placenta.
That raises the tricky philosophical question of what moral standing, if any, such balls of cells have.
“We’re not looking for a soul. The question is, ‘Does it have the (biological basis) for self-construction and self-organization, or is it a fundamentally disordered growth,” said Robert George, a Princeton professor of jurisprudence and a member of Bush’s bioethics council.