Stem Cell Politics: The NAS Prohibitions Pack More Bark than Bite

Frustrated stem cell scientists in the United States have responded enthusiastically to the voluntary guidelines for human embryonic stem cell research published by the National Academy of Sciences in April 2005. One likely reason for their considerable enthusiasm: the guidelines include very few prohibitions on embryonic stem cell research.

In fact, the NAS guidelines preclude only three research activities involving either human embryos or human embryonic stem cells: (1) the research use of human embryos beyond fourteen days (or the appearance of the primitive streak, if that comes first); (2) the creation of embryonic chimeras involving the transfer of human embryonic stem cells into nonhuman primate blastocysts or the transfer of any embryonic stem cells into human blastocysts; and (3) the breeding of any chimeras into which human embryonic stem cells have been transferred at any stage of development. None of these prohibitions is particularly prohibitive.

Currently, publicly funded stem cell research in the United States is severely restricted by the Bush administration's prohibition on the derivation of human embryonic stem cells using federal funds. By contrast, in most U.S. states, privately funded research is virtually unregulated. In the absence of a change in federal policy, scientists working with private or state funds could hardly ask for a better deal than the NAS voluntary guidelines. Scientists achieve the appearance of responsible self-governance and in so doing put pressure on the federal government to review and amend its stem cell research policy, which by comparison with the NAS guidelines now appears unnecessarily restrictive. All the while, current research funded privately or by states is essentially unimpeded.

As the authors of the NAS guidelines themselves acknowledge, the first prohibition—the fourteen-day limit on embryo research—merely reiterates a longstanding international consensus on the time frame for permissible research involving human embryos. The problem with this prohibition is twofold: from a practical perspective, it is irrelevant; from a political perspective, it is blatantly rhetorical. Practically, at present, it is not biologically possible to maintain the human embryo outside of the body beyond fourteen days, so the guidelines forbid research that is, for the foreseeable future, impossible. But politically—especially in the U.S. context, where embryo research is essentially contested—to call this a "prohibition" is to engage in sleight of hand, for a prohibition on impossible research is hardly restrictive.

Consider next the NAS prohibition on building certain kinds of part-human chimeras, those resulting from the transfer of human embryonic stem cells into nonhuman primate blastocysts and those involving the transfer of any embryonic stem cells into human blastocysts. This controversial practice is explicitly addressed in very few jurisdictions. The earliest guidelines on this kind of research were issued in 2002 by the Canadian Institutes of Health Research (Canadian counterpart to the U.S. National Institutes of Health). These guidelines include a comprehensive ban on creating part-human embryonic chimeras: no human embryonic stem cells, germ cells, or other cells likely to be "pluripotent" (that is, capable of differentiating into most of the body's cell types) may be combined with either a human or nonhuman embryo or fetus. In sharp contrast, the NAS guidelines permit, under certain circumstances: (1) the transfer of stem cells from any human or nonhuman nonembryonic source (such as cord blood, aborted fetuses, or somatic tissues) into nonhuman blastocysts (including primate blastocysts); (2) the transfer of human embryonic stem cells into all nonhuman animal blastocysts except those of primates; and (3) the transfer of stem cells from any human or nonhuman embryonic or nonembryonic source into the fetus or adult of any species, including humans. Reframed in this way, the proposed NAS prohibition is strikingly liberal. Indeed, the NAS guidelines appear to be the most permissive explicit guidelines in the world for this type of research.

Finally, there is the NAS prohibition on breeding chimeras. This prohibition is confusing because it is not exactly clear what the underlying concern is. If the concern is with chimeras breeding more chimeras, the concern is scientifically ill-founded. The expectation with chimeras...