The creepy solution to the stem-cell debate.
The good news is that we may have figured out how to solve the moral problem that's been holding up stem-cell research. The bad news is that the solution will introduce a whole new kind of horror.
That's the implication of this year's final two presentations to the President's Council on Bioethics. The first, by Drs. Donald Landry and Howard Zucker of Columbia University, proposes that we take stem cells from embryos at the same point at which we take organs from children and adults: right after they die. All we have to do is agree on the point at which an embryo is dead. Landry suggests that this point is "the irreversible arrest of cell division," which conveniently applies to huge numbers of embryos frozen in IVF clinics. With further study, he argues, we can clarify the signs of irreversible arrest, which will tell us when it's kosher to start yanking stem cells. He cites an experiment in which stem cells from arrested frog embryos were injected into normal frog embryos. Twenty-five percent of the cells began to divide again and were absorbed into the new embryos.
The conservatives on the council like the idea. They have two concerns. They want to make sure the signs chosen to certify embryo death don't exclude some living embryos. They're also wary of the Columbia team's suggestion that stem cells could be harvested from embryos "in extremis," i.e., near death. But Landry and Zucker point out that these are the same issues ethicists have worked out in the case of a dying child or adult. We just need to iron out the details. That's the beauty of the proposal: It's conventional.
The second proposal, presented by council member William Hurlbut, is exactly the opposite. It's brilliantly, grotesquely unconventional. Hurlbut, an earnest young member of the council's conservative wing, has been working for two years on a scheme to end-run the problem of killing embryos. He seems to be the only person in this debate who has figured out that the Catholic fixation on the technical definition of a human embryo, which stem-cell researchers regard as a roadblock, actually presents an opportunity. Instead of whining about the church's insistence on the continuity of personhood from embryo to adult, Hurlbut has seized on the point of discontinuity: the non-personhood of anything before or less than an embryo. If it isn't an embryo, it's fair game.
The distinction Hurlbut wants to draw and exploit is between a whole embryo and its parts. He quotes Thomas Aquinas to the effect that an animal's life resides in its wholeness. "A living being is more than the sum of its parts," he argues. But while humanity may lie in the whole, utility may lie in the parts. As Hurlbut puts it in his presentation paper, "Incompletely constituted or severed from the whole, subsystems with partial trajectories of development may temporarily proceed forward with a certain biological momentum." In other words, the parts of an embryo—or the parts that normally would become an embryo—might produce stem cells, even if, to avoid the moral problem, we kept these parts incomplete or severed.
How could we create functioning parts of an embryo without the whole? By turning off one of the genes that guide embryo formation. Hurlbut's first choice is the human equivalent of cdx2, the gene in mice that directs the formation of the placenta. Without cdx2, the embryonic mouse cells divide but fail to take the shape of a mouse. The plan would be to follow the recipe for cloning—put the nucleus of a body cell into a gutted egg cell—but turn off cdx2. Then, once the cell begins to divide, reactivate the gene, too late to organize the embryo but early enough to make stem cells.
It sounds perfect, until you look up at the projection screen. Hurlbut has modeled his recipe on "aberrant products of fertilization" and teratomas, which, he explains, are "germ cell tumors that generate all three primary embryonic germ layers as well as more advanced cells and tissues, including partial limb and organ primordia." Limb and organ primordia? Yep, that's what's on the screen: a ball of tissue, grown inside some poor creature, full of bits and pieces of what would have been a body. Another slide shows an X-ray image of somebody's back. To the left of the spine, you can see a cluster of white spots that look like teeth. And that's exactly what they are, all dressed up and no place to chomp. You wanted disorganized development? You got it.
The things Hurlbut wants to create wouldn't get that far. And the important thing, from the standpoint of solving the stem-cell debate, is that they wouldn't be embryos. Hurlbut calls them "biological entities" or "pseudo-embryos," but he prefers the term "biological artifacts," which marks them, in his view, as "a human creation for human ends." They would have "no claim on the moral status due to a developing human life," he writes. James Q. Wilson, a council member who likes the idea and loves to garden, puts it more succinctly. The product of Hurlbut's technique, he suggests, would be "a weed."
The idea is so wild that others on the council, who usually know where they stand on embryo issues, aren't sure what to think. Gilbert Meilaender, a leader of the conservative bloc, worries that if it's OK to booby-trap the first week of embryonic development, it might become acceptable to booby-trap the eighth. Hurlbut says the sabotage he envisions would prevent the artifact from getting that far. But a footnote in Hurlbut's paper suggests the slope is slippery. "One could rightly argue that later deficiencies in axes formation, alignment of basic body plan and organogenesis also reveal a level of disorder that precludes organismal existence," he writes. If knocking out cdx2 doesn't work, he holds out the possibility of knocking out a different gene, Hnf4, "which is crucial to normal gastrulation." That would be two weeks into development, and Hurlbut has a list of other genes worth trying. His moral logic doesn't stipulate when the sabotage of embryonic development has to take effect. It only requires that the sabotage be done beforehand.
Paul McHugh, one of the council's moderates, finds the idea gruesome. He calls the proposed creation a "weird genetic hybrid" that is "very embryolike" and has been engineered to die. Hurlbut replies, coldly but correctly, that according to the technical definition favored by opponents of stem-cell research, the thing can't die because it was never alive. Leon Kass, the council's chairman, agrees, describing the thing as a "re-engineered entity" that is "embryolike" but not "embryonic." Michael Gazzaniga, the council's most liberal member, calls Hurlbut's strategy a perversion of science. Instead of tinkering with language to fit biology, he observes, Hurlbut is tinkering with biology to fit language.
Will Saletan covers science, technology, and politics for Slate and says a lot of things that get him in trouble.
Illustration by Mark Alan Stamaty.