Breakthrough embryo research puts 14 day rule in spotlight

The legal and ethical implications of human embryo research are set to make waves once more, with breakthrough research drastically extending how long petri dish embryos can survive. Two experiments have shown that lab-grown embryos – in both cases using donated human cells – could be kept for significantly longer than with any previous technique.

Teams at the University of Cambridge and the Rockefeller University borrowed processes previously developed with mice embryos, coaxing the cells past day seven, where in a body they would be implanting in the wall of the uterus.

Currently, international law prevents lab-grown embryos from being kept for any longer than fourteen days. Indeed, the two research projects ended their respective experimentation on day thirteen, so as not to contravene those regulations.

It's that two week limit that is likely to come into question now. Previously, no experiment had kept a living, lab-grown embryo feasible to even ten days; now, it's unclear just how long the projects could have continued were the rules not in place.

Already, indeed, some scientists are questioning whether the fourteen day limit is as relevant as it was once thought. It had been established in respect of the "primitive streak" – the feature that develops, at around fifteen days, that will define bilateral symmetry among other things – but, a group of researchers argue, should be reconsidered.

"The formation of the primitive streak is significant because it represents the earliest point at which an embryo's biological individuation is assured," Insoo Hyun, Amy Wilkerson, and Josephine Johnston wrote in an op-ed in Nature. "Before this point, embryos can split in two or fuse together. So some people reason that at this stage a morally significant individual comes into being."

However, they continue, that's an arbitrary decision. Some might consider an embryo to be an individual at the point of fertilization; others would save that classification until the growing cells can experience pain, or respond to external stimuli.

"The 14-day rule was never intended to be a bright line denoting the onset of moral status in human embryos," they argue. "Rather, it is a public-policy tool designed to carve out a space for scientific inquiry and simultaneously show respect for the diverse views on human-embryo research."

It's almost certain to provoke strong feelings on all sides of the argument. On the one hand, the research has potentially huge implications for the understanding of how early stage miscarriages take place, as well as how twins are formed, among other issues.

On the other, there's unlikely to be consensus on religious and moral grounds about when an embryo is considered an individual and when it's simply a cluster of cells.

Earlier this year, a UK team successfully petitioned to have permission to genetically modify human embryos, though on the understanding that they would not be implanted.

Late in 2015, meanwhile, the Organizing Committee for the International Summit on Human Gene Editing concluded that advances in genetic modification must wait until the ethical framework catches up with the science.

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IMAGE The Rockefeller University