The proposed guidelines on federal funding for stem-cell research issued in April by the US National Institutes of Health (NIH) are a welcome effort to assert ethical and regulatory leadership over this field — especially given the vacuum in oversight left by the previous US administration. Yet concerns aired by the scientific community during the public comment period that closed last week have underscored the need for the NIH to revise the guidelines to allow the responsible progress of research.

For example, the NIH has acted admirably in setting forth nine strict informed-consent provisions regarding the source material for stem-cell lines that are eligible for federal funding. As currently written, however, the provisions would probably exclude funding for most embryonic stem cells now in use, because the cells were derived from leftover embryos at fertility clinics under rules less stringent than the ones now called for. In particular, one provision requires that embryo donors affirm that they are donating “without any restriction or direction” regarding the patients who may benefit from the research. Few of the consent forms currently in use by fertility clinics ask for that affirmation. Also absent from many forms is the stipulation that the donors “would not receive financial or any other benefits” from commercial development of the research.

It is doubtful that the guidelines are intended to bar future NIH funding from stem-cell lines that are currently eligible — or, indeed, from the hundreds of lines that are now in use but are not among the score of US-approved lines. That would contradict US President Barack Obama's intention, stated on 9 March, to “expand NIH support for the exploration of human stem cell research”. The NIH should explicitly state that the informed-consent provisions apply only to newly created lines. All previously eligible lines should continue to be eligible, and existing non-eligible lines should become so — provided that the latter were created in accordance with guidelines issued by the US National Academies or the International Society for Stem Cell Research.

A much less clear-cut issue is whether federal funding should support work on lines created from sources other than leftover embryos. The NIH's draft guidelines currently exclude support for research on lines created through somatic-cell nuclear transfer (SCNT), also known as therapeutic cloning. And they prohibit funding for lines created through the generation of an embryo from an unfertilized egg cell.

Some investigators have protested this provision of the guidelines, arguing that the NIH should not cut off any avenues of research. Their contention is somewhat hypothetical, however, because no one has yet shown conclusive evidence that SCNT can successfully create a human embryo. Regardless of this, the ethical issues involved are extremely sensitive. Polls consistently show that a majority of the American public is willing to pay for research on stem cells derived from embryos that would be discarded otherwise. But it is not clear that a majority would support the use of taxpayers' money to study stem cells from embryos created and destroyed for research purposes alone. So unless the scientists arguing for federal funding of research on SCNT-derived stem cells can make a much stronger case, by spelling out the specific situations in which the research might be warranted and explaining how they will ensure proper oversight of the work, the NIH's proposed exclusion should stand.

At the same time, however, the NIH should affirm that it will revisit its draft guidelines as the science progresses. The past decade shows us that basing research policy on arbitrary cut-off dates does not serve science or the public interest well.