Is the 14-day limit on growing embryos out of date?

Michael Cook
March 25, 2017
Reproduced with Permission

Both in the US and UK, growing human embryos more than 14 days in a laboratory is banned. Recent developments suggest that it may be possible to grow them for longer and a number of scientists are lobbying to extend the limit. They contend that the limit is out-of-date and too restrictive.

But what if they could create embryo-like structures without creating complete embryos? This possibility is completely unregulated.

This is why John D. Aach and George Church and others from Harvard Medical School say that ethical guidelines for synthetic human entities with embryo-like features (SHEEFs) are needed. It might be possible to create a human heart and a rudimentary human brain, for instance. What if the brain is conscious, or could feel pain?

Research limits designed for embryos will not work for SHEEFs because "it will soon become possible to generate SHEEFs that can bypass canonical embryonic stages through the use of completely different laboratory operations".

The 14-day rule was a hard-fought compromise between different ethical views of the embryos but at least the participants in the debate understood what an embryo was. "SHEEFs might present novel combinations of such features that are very unlike those of embryos, and are so new and unfamiliar that traditions may be puzzled and unable to offer articulated opinions about them."

In an article in the journal eLife , Aach and his colleagues call for a wide-ranging discussion about the ethics of creating SHEEFs. They compare the 14-day rule to a stop sign at the end of a research road. What scientists need now is a perimeter fence surrounding experiments on SHEEFs to prevent researchers from straying into unethical territory.

"I absolutely support this," Cambridge University biologist Magdalena Zernicka-Goetz told NPR's Shots . "The time is right to begin discussion of these issues in a forum that includes scientists and has a wide representation of society."