Embryonic stem cells hold great promise for treating diseases, but face many scientific and ethical hurdles.Credit: STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY

In an intensifying race to grow embryonic stem cells matched to patients, Harvard researchers announced on 6 June that they had cleared two year's worth of regulatory hurdles to start such work. They plan to ask women to donate their eggs for the research.

The team wants to create human embryos containing DNA from patients with diabetes or neurodegenerative disease, and then extract embryonic stem (ES) cells from them. They aim to find out whether and how these diseased ES cells behave differently from healthy ones, in order to learn what goes wrong as the conditions develop and perhaps find new ways to treat them.

The work is highly controversial because human embryos are discarded in the process, and American researchers are banned from using federal research money for such studies. In addition, the only research claiming to have successfully produced human ES cells using this method was fabricated by South Korean scientist Woo Suk Hwang.

The announcement also comes at a time when political restrictions on human ES cell work are becoming a hot issue in the run up to the US elections in November (see 'Election fever inflames the US stem-cell debate').

Because of the intense interest, Harvard researchers say that it took more than two years of review by eight committees to gain regulatory clearance for their work, which is paid for by private donations. Because "these are indeed extraordinary times," the researchers decided to announce the start of their project rather than wait until they had peer-reviewed results, said Harvard University provost Steven Hyman at a press conference.

The team will join some half a dozen groups around the world already working to grow human ES cells from cloned human embryos. "The more labs that are doing this, the more likely we'll have success," says Arnold Kriegstein who directs a stem-cell biology programme at the University of California, San Francisco, in which similar work has just started.

Good eggs

The discovery that Woo Suk Hwang's research was fraudulent left a scientific vacuum: no one actually knows whether it is possible to use the technique of somatic cell nuclear transfer, often called cloning, to make a human embryo and then extract stem cells.

In such experiments, DNA from a patient's cell is inserted into a human egg from which the nucleus has been removed. The resulting embryo is grown for a few days into a blastocyst, and then embryonic stem cells are extracted and grown in culture. So far only one group, in Newcastle, UK, has reported that they grew a cloned human embryo into a blastocyst, but they did not extract ES cells¹.

One of the biggest obstacles to these experiments is obtaining enough human eggs. The studies in San Francisco and Newcastle are using eggs that failed to fertilize during in vitro fertilization (IVF). But these eggs may be hard to work with precisely because they did not fertilize and because they come from women with fertility problems.

Two of the Harvard University researchers, Doug Melton and Kevin Eggan, are going to take a slightly different tack: they will also ask healthy women in the Boston area to donate eggs specifically for research, without payment. Whether or not women will be willing to undergo this invasive procedure, "we simply don't know and we'll have to wait and see," Eggan says.

One of the Harvard researcher's immediate aims is to use skin cells from diabetic patients to grow ES cells. Watching these stem cells behave is a little like replaying what happened when that person grew from an embryo into an adult. It might reveal when and why the cells start to veer away from normal development, giving rise to a pancreas that is liable to fail and stop making insulin. "We can move studies from patients to the Petri dish," says Melton.

Researchers hope that these cells could also be used to test new drugs. Another goal is to fix genetic defects in embryonic stem cells that may, for example, be the cause of a patient's blood disease. The cells would then be used to grow healthy blood cells that could be transplanted back into the patient.

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• References

  1. StojkovicM., et al. Reprod. Biomed. Online, 11. 226 - 231 (2006).