Controversial embryonic stem cell paper clarified

The journal Nature this week published clarification of a controversial research paper which claimed that embryonic stem cell (ES cell) lines could be produced by extracting a single cell from an early embryo without destroying the embryo. Dr Robert Lanza of US biotechnology company Advanced Cell Technologies and his team used an approach similar to PGD to remove a single cell from an early embryo. A number of single cells removed from early embryos were then grown in culture to generate ES cell lines. The results showed that it was possible to create stem cell lines without needing to destroy embryos, however in the experiment the team had used multiple cells from individual embryos to minimise the number of embryos used. All of the embryos used in the research were, in fact, destroyed.

The usual method of creating ES cell lines uses later embryos than those used in Lanza's work, and always results in the embryo being destroyed. The work was criticised by Catholic Bishops in the US, and by supporters of stem cell research in Congress, who said that the fact that embryos were destroyed to demonstrate the principle that single cells could be used to derive cell lines, hurt their cause. The clarification in Nature affirmed the scientific validity of the research but also itemises changes that have been made to the text that were misunderstood or mis-stated at the time. Primarily the clarification addresses the claim that others could use the technique to create cell lines without harming embryos, whereas Lanza and his team had in fact destroyed the embryos on which they worked. If the researchers had taken only a single cell from each embryo, a much larger number of embryos would have been needed to generate the number of cell lines they successfully derived.

Nature's chief biology editor, Dr Ritu Dhand, commented, 'There was nothing either scientifically or technically wrong with the paper'. The paper was also subjected to a second round of peer review to check that everything was in order. In the clarification the authors point out that they have not excluded the possibility that only a subset of the cells from early embryos can form human ES cell lines. Another possible caveat to the research pointed out in the clarification is that the isolated cells from the original embryo were cultured in the same medium as the parent embryo. The authors suggest that, 'diffusible factors from the other blastomeres present in the media may assist recovery and growth'. Despite this the authors assert that, 'these caveats are worth considering for future studies, but do not negate our central finding that blastomeres extracted from an 8-10 cell embryo by mechanical micromanipulation can form human embryonic stem-cell cultures'.