Scientists from Advanced Cell Technology (ACT) caused an uproar in 2006 when they reported that they could generate embryonic stem cells from a human embryo without destroying it, thereby sidestepping the ethical disputes that have mired the field since its inception. While they did create stem cells, and the embryos theoretically could have survived the process, they did not actually survive.

Now scientists at ACT, led by chief scientific officer Robert Lanza, have repeated the feat, developing five embryonic stem-cell lines without destroying the embryos from which they were derived. The researchers plucked a single cell from an early-stage embryo, mimicking a procedure performed during preimplantation genetic diagnosis to determine if the embryo carries harmful genetic mutations. They then transformed that cell into a line of embryonic stem cells by exposing it to chemical factors that mimic the developmental environment. The findings are published today in the journal Cell Stem Cells.

The technique might make new stem-cell lines available to researchers who are supported by government grants. In 2001, President Bush limited federal funding to stem-cell lines already in existence. But many scientists have objected to this limitation, saying that these stem-cell lines are flawed. In a press release issued by his company, Lanza says,

This is a working technology that exists here and now. It could be used to increase the number of stem cell lines available to Federal researchers immediately. We could send these cells out to researchers tomorrow. If the White House approves this new methodology, researchers could effectively double or triple the number of stem cell lines available within a few months. Too many needless deaths continue to occur while this research is being held up. I hope the President will act now and approve these stem cell lines quickly.

Over 80% of the biopsied embryos formed healthy blastocysts, a rate consistent with or higher than previously reported for both biopsied and normal (non-biopsied) embryos. These results are consistent with the fact that thousands of healthy children have been born following the use of PGD testing in IVF clinics worldwide.

However, it's not yet clear if fertility doctors would embrace the technique. When Lanza's team published its initial findings in 2006, doctors said that despite the apparent safety of the biopsy technique used during preimplantation diagnosis, patients undergoing in vitro fertilization would likely be unwilling to subject their embryos to procedures that would not directly benefit their own family, as is the case with preimplantation diagnosis.

The other option would be to apply the technique to the thousands of leftover embryos languishing in frozen storage at fertility clinics. (Parents often generate more embryos than they use.) These embryos could theoretically be biopsied for single cells and then returned to storage. Whether or not that frozen limbo satisfies ethical opponents of embryonic stem-cell research is another matter.