Time limit on lab-grown human embryos is relaxed by experts


The ban on growing human embryos in the lab beyond 14 days has been relaxed by an international body of experts, paving the way for research that could help to unpick issues ranging from why recurring miscarriages occur to improving IVF.

The decades-old rule is laid down in the law in a number of countries, including the UK and Australia, and was previously stipulated in guidelines from the International Society for Stem Cell Research (ISSCR). These guidelines set out standards that are used by scientists, journals and research bodies around the world, and can also influence policymakers.

But the ISSCR has relaxed its stance, saying embryos may be cultured beyond 14 days, provided a robust, specialised review of the proposed experiments is undertaken – with the research deemed scientifically justifiable with no suitable alternatives – and there is broad public support and local regulations permit it. Specialised review is already required for research involving embryos up to 14 days.

“We want there to be no doubt: this is not a green light for groups to go ahead with extending human cultures beyond 14 days. It would be irresponsible and in many jurisdictions it would be illegal to do so,” said Prof Kathy Niakan, of the University of Cambridge and Francis Crick Institute, who was involved with the development of the guidelines.

“The guidelines are a call to proactively engage in a two-way dialogue with the public to review the 14-day limit of human embryo culture.”

When the 14-day rule was introduced it was difficult to culture human embryos beyond about five days. But science has advanced: in 2016 researchers revealed they had managed to keep human embryos alive and active for 13 days.

Scientists say that being able to study embryos beyond 14 days could bring a wealth of benefits, from validating the use of clumps of human cells to study early embryo development to aiding efforts to judge the safety of techniques such as mitochondrial replacement therapy, and providing new insights into recurring miscarriages and congenital abnormalities.

“You can also make the ethical argument that given the importance of this [14-28 day] period to human development, we have to understand this – it is sort of unethical not to understand what is going on in our early development,” said Robin Lovell-Badge, the chair of the ISSCR guidelines taskforce and senior group leader at the Francis Crick Institute.

The team added there would no longer be a “hard stop” in terms of days beyond which the culture of human embryos is prohibited, although the further researchers want to develop human embryos, the tougher it will be both technologically and to gain approval.

The ISSCR guidelines cover other areas of research including the use of genome editing techniques with human embryos and work involving the development of chimeras, whereby human cells are introduced into embryos of other species.

Daniel Brison, a professor of clinical embryology at Manchester University who was not part of the taskforce, said culture of human embryos beyond 14 days would require a change of law in the UK, but a change “undoubtedly has scientific and clinical merit”.

Dr John Appleby, of Lancaster University, agreed. “Relaxing the 14-day rule is a good idea. It is essential to the ethical progression of science,” he said.

But Brison stressed the importance of engaging with public opinion, noting the 14-day rule was introduced in the 1980s because it is the point in human development when individual identity is assumed because the embryo can no longer split into twins.

“As scientists it is essential that we are seen not to be changing this rule simply because we now have the technical ability to work beyond 14 days, but instead because we can demonstrate that the public support the aims of the research,” he said. “Without this clear public backing, we risk being accused of changing the rules out of expediency.”



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