LONDON – New guidelines released on Wednesday remove a decade-old barrier to stem cell research, recommending that researchers be allowed to grow human embryos for longer under limited conditions.
The “14-day rule”, an international ethical standard that restricts laboratory tests on human embryos, has existed for decades and has been enshrined in law in countries such as Great Britain and Australia. Previously, scientists had to destroy human embryos grown in a laboratory before they were 14 days old.
Some researchers have preferred to revise the rule to study the development process further, while opponents say such experiments cross a moral line at any stage and it is unclear whether the change would spur research.
The original limit was arbitrary and prevented investigation of a critical period in embryonic development – typically between 14 and 28 days – said Robin Lovell-Badge, stem cell expert at London’s Crick Institute and chair of the group behind the new guidelines.
“We believe that many congenital abnormalities develop very early in this period,” said Lovell-Badge. “With a better understanding of these early stages, we may be able to use simple techniques to reduce the level of suffering.”
The guidelines, last updated in 2016, were issued by the International Society for Stem Cell Research, whose standards are widely accepted by countries, medical journals and the research community. There was no indication of how long more embryos could be grown.
In order for scientists in the UK to start making embryos after two weeks, the law regulating this research would need to be amended. Any relaxation of the rule would still require a “robust review” by national regulators, Lovell-Badge said.
It is “not a green light” for scientists to expand research on human embryos, said Kathy Niakan of Cambridge University, who helped draft the guidelines, adding that “would be irresponsible”.
Niakan said there needs to be a public dialogue between academics, regulators, funders and the public to discuss possible objections. She said there needs to be broad public support before work continues and that countries may also use a special oversight process to weigh the scientific merits of the research.
Marcy Darnovsky, executive director of the Center for Genetics and Society, said the scientific rationale for the new guidelines is still lacking.
“If an embryo is in a petri dish outside the body, can you really say anything meaningful about miscarriages or embryo development?” She said.
Darnovsky was also concerned that the guidelines did not put a limit on how long human embryos could potentially be grown.
The Society also advised on other controversial stem cell issues, including the need for tight controls for the transfer of human embryos to the uterus after mitochondrial donation – a process that uses two eggs and one sperm to create an embryo.
For now, the guidelines forbid any genetic manipulation that would pass changes on to future generations – similar to the work of Chinese scientist He Jiankui, who stunned the world when he announced in 2018 that he had made the first genetically engineered babies.
Such work is currently banned, but Lovell-Badge and others acknowledge that one day it may be allowed “if proven safe enough and used in sufficiently limited circumstances,” said Hank Greely, director of the Center for Legal Affairs and Life Sciences at Stanford University.
The guidelines also prohibit human cloning, the transfer of human embryos to an animal uterus, and the creation of human-animal chimeras.