Draft guidelines on stem cell funding issued by the US National Institutes of Health (NIH) in mid-April might block federal funding for experiments that rely on certain commonly used stem cell lines.

“I think our main concern is that some perfectly valid lines don't get ruled out on a technicality,” says Geoff Lomax, a lead member of the Interstate Alliance on Stem Cell Research (IASCR), an organization established in 2007 to promote stem cell research collaboration.

The proposed guidelines would allow funding only for research using stem cell lines derived from unused embryos originally created for in vitro fertilization. They also require that the donors of those embryos give informed consent for their use. However, many of the lines commonly used today—including some of the lines allowed under the strict Bush administration guidelines—technically don't satisfy these requirements.

The IASCR along with the International Society for Stem Cell Research, the Center for Genetics and Society and the Harvard Stem Cell Institute have requested that the NIH incorporate a clause such that these stem cell lines would be grandfathered in.

The proposed guidelines also deny support for parthenogenesis and somatic cell nuclear transfer (SCNT). SCNT is used in animal research, but no known human stem cell lines have been developed from the technology.

“Some don't like the idea that SCNT has been cut—presumably on the rationale that it could be used for cloning humans,” says Larry Goldstein, director of the University of California–San Diego stem cell program. “But [it's] a hypothetical argument at the moment.”

The California Institute for Regenerative Medicine and Harvard Stem Cell Institute both offer funding for research involving parthenogenesis and SCNT.

“After meeting with the NIH, the impression many of us came away with was that these guidelines are seen as a working compromise that has room for change as science and political winds shift,” says Lomax. “The emphasis is on getting something to work now, and these guidelines are a good start.”

The commenting period for the guidelines closed on 26 May. The NIH will release its final version of the guidelines on or before 7 July.