When should a developing embryo be defined and treated as a living entity, and at what point do scientists risk taking a human life during their research?
These fundamental questions are being reconsidered by scientists, ethicists and policymakers around the world, with renewed discussions driven by rapid scientific advances and the lure of exploring the unknown.
The global rule adopted by China, the US, Britain, France, Spain and a host of other countries – that human embryos cannot be kept alive in a laboratory beyond 14 days – was theoretical when it was introduced in 1984.
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But in the past five years, a growing number of labs – including some in China – have been able to push the cultivation process from just a few days to within reach of the 14-day limit.
Loosening the restrictions
In 2021, the US-based International Society for Stem Cell Research (ISSCR) became the first scientific body to try and loosen the restriction, with a new guideline suggesting a longer period of embryo culture could be acceptable.
According to the guideline, a specialised scientific and ethical oversight mechanism should be used to decide whether the extension is required or justified by the research goal “if local norms and regulations allow and there is broad public support”.
China was quick to act on the change. In the same year, the Chinese Academy of Sciences (CAS) appointed and funded a handful of scientists to research the issue, according to Tan Tao, one of the participants.
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“Since 2019, there have been intensifying voices in the academic community talking about whether or not the 14-day rule should be pushed forward,” he said.
Tan, a professor at the Institute of Primate Translational Medicine at Kunming University of Science and Technology (KUST) in Yunnan province, said the research included several rounds of discussions among the scientific community.
In their findings published in November, the researchers – led by senior zoologist and CAS academician Ji Weizhi, who also works at KUST – suggested policymakers consider a “reasonable” extension of the 14-day rule if cases were “thoroughly justified and evaluated”.
The paper, which appeared in the Bulletin of the Chinese Academy of Sciences, specifically proposed that research on human embryos could be allowed to continue for 25-28 days.
However, the Chinese researchers said experimentation must be stopped earlier if the embryos developed a heartbeat or neural tube – considered important biological characteristics that distinguish an embryo from a human being.
The researchers said scientific advances had led to updated knowledge and evidence that may challenge the established rules and ethics.
In the 1980s, for example, it was accepted that the nervous system develops between 17 and 22 days after fertilisation. However, recent findings suggest that functional connections between nerve cells do not form until after day 42, they said.
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‘Treat human embryos with extreme caution’
Zhai Xiaomei, executive director of the Centre for Bioethics at the Chinese Academy of Medical Sciences, said the paper’s recommendations “reflect more the attitudes and needs of scientists”.
“Evidence of scientific necessity and great medical value must be presented [if scientists propose to exceed the 14-day convention], and we still need to treat human embryos with extreme caution,” she said.
Zhai, who is also a member of the ISSCR’s ethics committee, said the community should always chew on the question of whether humanity should do whatever it can do.
Speaking in her ISSCR role, Zhai said the society’s position was clear – “that an extension should be considered only when necessary and sufficient conditions have been met”.
Scientists in Britain are also calling for a review of the 14-day rule, with the Babraham Institute’s Peter Rugg-Gunn highlighting the potential health benefits, particularly in cases of recurrent miscarriages, in an interview with The Guardian last month.
“We are at the point now where technically these experiments are probably possible,” he said.
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“There is a very high likelihood that if research could continue, the new knowledge would have benefits to health.”
In the US, the topic has also stirred discussion, with some states considering relaxing the limits, according to Wu Jun, an associate professor at the University of Texas Southwestern Medical Centre’s molecular biology department.
But he added that each state, and even individual research institutions, has the discretion to set its own policies, although there would be a consensus at the federal level.
The origin of the embryo debate
The debate originated with the birth of the world’s first “test tube baby” in Britain in 1978, and included the ethics of embryo disposal, as well as the research possibilities that were opening up.
The issue’s complexities mirror the abortion discussion – a crossroads where different cultural, scientific, religious, ethical and other value judgments collide – and this is reflected in the range of policies adopted by different countries.
The 14-day rule – enacted into law in Britain in 1990 and endorsed by the US National Institutes of Health in 1994, with other countries following – aimed to strike a balance between the potential benefits of research and the special status of the human embryo.
China did not introduce the rule into its regulatory framework until 2003, leading to some international criticism. Also, unlike the US – where some states ban abortions and all embryonic research – China’s women have a universal right to access abortion.
Wu, who works in Texas where abortions and embryonic research are banned, said one reason that China is at the forefront of the field could be its “relatively lax administrative policies”.
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A biologist working in embryonic research, who declined to be named because of the issue’s sensitivity, said he did not expect China to be the first country to lift the 14-day restriction.
“China may wait until the UK or the US take this step first and then follow up,” he said, adding that the country may be reluctant to appear too radical on the ethical front, especially after He Jiankui’s gene-edited baby scandal of 2018.
China ‘should be cautious’ with law
A Chinese academic in the field of scientific ethics, who also asked for anonymity, said China should be cautious about changing its policy on scientific embryo research.
In the race to occupy the high ground in science and technology, Chinese scientists had sometimes given the negative impression that they do not follow the rules and do “whatever they want”, he said.
This perception, along with loopholes in ethics regulations, had made China an easy target for “ethical dumping”, the practice by some developed countries of conducting research in Chinese labs that would be unacceptable at home, he added.
An extension of the 14-day rule is not only becoming technologically feasible, scientists argue that it could open the “black box” of human development – the crucial period between two and four weeks about which little is known.
Scientists who study the earliest stages of life have gained insights from pregnancy scans and materials donated from terminations, but are prevented by the rule from direct observations of embryos in this developmental window.
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They argue that an extension could uncover the causes of miscarriages as well as congenital conditions that may have their origin in the complex changes occurring in embryos at the two- to four-week stage.
“This is the most important stage in human development,” said Wu, from the University of Texas.
“Embryos start organising cells to form organs and many birth defects – such as congenital heart disease – occur, so studying this period can give scientists clues to potential disease causes.”
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