Given the breadth of their potential, one might expect that human embryonic stem (ES) cells would be the focus of attention for hundreds of research groups. But so far, only a dozen or so teams have entered the field. The issue was initially one of a shortage of cells. But now the main problems are political — with fears that the new US administration will ban federal funding for ES-cell research looming large.

So far, the main distributor of human ES cells has been the WiCell Research Institute, a non-profit spin-off from the University of Wisconsin in Madison, where in 1998 the cells were first cultured in James Thomson's lab2. His work was funded by the company Geron of Menlo Park, California, which has certain exclusive commercial rights to develop the ES cells for therapeutic applications.

In February last year, the University of Wisconsin announced that WiCell would soon start making Thomson's ES cell lines available to other research groups. Some researchers were initially concerned that WiCell wanted wide-ranging rights to rescind permission to work on the cells and to demand that they be destroyed. Those rights have since been restricted, and will only be enforced under specific circumstances — for instance if researchers use the cells for additional projects without written permission.

Given the time that has elapsed between the cells' creation and WiCell's formation, say stem-cell researchers, Geron got an important head start. Although researchers who use WiCell's ES cell lines can patent discoveries made using the cells, they may find that much of this territory has already been staked out. “We have submitted 36 patent filings on these cells,” says David Greenwood, Geron's senior vice-president for corporate development.

Other supplies are now available. A group headed by Alan Trounson at Monash University, near Melbourne in Australia, is responding to requests to obtain cells from its human ES cell lines6 — although high demand is putting the lab under pressure. “We are short on staff,” says Trounson. Other ES cell lines are soon expected to become available from the Rambam Medical Center in Haifa, Israel.

But increased availability does not mean open access. Current legislation in France and Germany, for instance, prohibits embryo research, including work on ES cells — although the French government is proposing to lift its ban. In the United States, meanwhile, uncertainty as to whether federal funds will be freed to support ES-cell research is hampering progress.

Last summer, the previous US administration concocted a compromise that would allow researchers to use federal funds to work on ES cells, provided the ethically contentious step of isolating the cells from a human embryo had been achieved using other funding sources. But President George W. Bush's administration may now block the use of federal funds for ES cell research. And in the current state of limbo, few scientists have responded to a call from the National Institutes of Health (NIH) for ES-cell research proposals. By the 15 March deadline for documents to show that proposed research will comply with NIH guidelines, just three submissions had been received.

Even if federal funding is released, there may still be problems. The NIH has published criteria — including standards for informed consent from 'parents' of the embryos from which the cells were harvested — with which suppliers of ES cells to federally funded researchers must comply. WiCell's current cell lines do not meet these standards, and the NIH is still reviewing compliance documents submitted from Monash.