Opening the door to new scientific achievement as well as ethical questions, an international body overseeing stem cell research has lifted a ban on growing human embryos beyond 14 days in laboratories.
(CN) — A decades-old barrier on stem cell research was loosened on Wednesday when an international panel of scientists, ethicists, clinicians and lawyers approved the growing of human embryos for more than two weeks in laboratories.
The International Society for Stem Cell Research said it was time to update its guidelines to reflect the current state of science and allow human embryos to be grown in laboratories beyond 14 days under limited conditions and with the public’s support.
The update was announced at a news conference in London. The ISSCR is an international body whose standards are widely accepted by medical journals, the research community and influence policymakers, but are not legally binding. Countries instead set their own ethical and scientific standards. For example, while the United Kingdom and Australia placed the so-called “14-day rule” into law, the United States has not.
The 14-day rule was proposed about 40 years ago when stem cell research was at its infancy and scientists were unable to culture human embryos for more than a few days — a limit that has held true until only recently. Whether because of ethics or statute, scientists have been bound before now to destroy human embryos grown in a lab before they reach 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,” Kathy Niakan, an expert at the University of Cambridge and Francis Crick Institute who helped draft the guidelines, said at the London news conference.
The international body said stem cell research has arrived at a point where lifting the 14-day limit can be both ethical and help scientists better understand how to prevent miscarriages, cure infertility and treat genetic diseases.
“Up to now, the 14-day rule has served science well,” Robin Lovell-Badge, the chair of the ISSCR panel, wrote in a Nature article explaining the update to the guidelines. “It has allowed research that is essential for many assisted-conception techniques to proceed in the face of strong opposition, notably from religious groups.
“Even scientists who saw value in experiments beyond 14 days, and viewed the time limit as arbitrary, were reluctant to discard a workable compromise made with public input.”
In some quarters, the deep reservations about stem cell research rest generally on ethical, religious and scientific grounds. There are fears this branch of science is being misused, and critics say it needs to be rigorously constrained. Concerns about stem cell research leading to gene-editing babies are one example.
The ISSCR did not set a new limit on how long embryos can be grown and instead laid out a series of conditions researchers should meet before being allowed to study embryos beyond 14 days. The 14-day cutoff was deemed important because, beyond this point, embryos show the first signs of developing a central nervous system. It is also a stage in human development when an individual identity is assumed to form because the embryo can no longer split into twins.
The new guidelines forbid, for now, any genetic editing that would pass on changes to future generations — similar to the work done by Chinese scientist He Jiankui, who stunned the world when he announced in 2018 he had made the first gene-edited babies. They also prohibit human cloning, transferring human embryos into an animal uterus and the creation of human-animal chimeras, saying such work “lacks scientific rationale or is ethically concerning.”
Calling it time now to update the guidelines and make them more nuanced, Lovell-Badge said researchers in the past five years have proven they can keep human embryos alive in culture longer than once thought possible and developed techniques to make stem cells model embryos and organs.
“Perhaps most striking is the creation of animal–human chimaeras by injecting cells from one species into an early-stage embryo from another species,” wrote Lovell-Badge, who is also a stem cell expert at London’s Crick Institute.
Offering an example, he suggested this research might one day allow researchers to produce a human heart from a pig. He said researchers are also experimenting with making eggs and sperm from stem cells, editing genomes and replacing organelles, which are critical subunits of a cell.
For Lovell-Badge, the 14-day limit blocks science from reaching the next horizons in stem cell research.
“It prevents study of a critical period, between 14 and 28 days, when the beginnings of tissues are established,” he wrote. “Processes that go awry during this time are thought to cause recurring miscarriages and congenital abnormalities, for example those of the heart and spine.”
He added that lifting the 14-day limit allows clinicians to make crucial comparisons between new “embryo models” they are developing based on stem cell structures with actual embryos.
“Comparing them with actual human embryos is the best way to assess their relevance and use them for experiments that might otherwise require embryos,” he said.
While Lovell-Badge considers it time for a change, he said proposals to study embryos beyond 14 days need to undergo a review and approval process by institutions or national bodies.
“Importantly, each proposal should be judged individually, on whether the research is justifiable in terms of the value of the information obtained, whether there are alternative ways to obtain the information and so on,” he said. “The more embryos that would be used, or the longer they would be kept in culture, the higher the bar.”
The panel also said the public must approve proposals to grow embryos beyond 14 days. Such approval, the panel suggested, could come from public opinion polls and citizen panels.
The panel said these guidelines add nuance to its previous standards, which laid out three broad categories of experiment: banned, permitted with special review and generally permitted.
Lovell-Badge said breeding animals with human gametes should be banned on ethical and scientific grounds but the new guidelines could allow heritable genome editing to take place if it’s shown to be safe and garner public support.
He said the guidelines “discourage premature commercialization of stem-cell-based interventions, and propose ways to curtail the activities of rogue clinics that offer untested, unsafe interventions with no basis in science.”
While lifting the 14-day rule means more oversight, he said relaxing the rule is valuable.
“Blanket bans enshrined in law appeal in their simplicity, yet leave the public worse off, and are more vulnerable to dogma or instinct rather than evidence,” he wrote. “Guidelines from international scientific societies can offer leadership in reassuring scientists and the public.”
Some scientists and groups question the need to lift the 14-day ban, saying the scientific value of doing so is murky and raise serious ethical questions.
“When an embryo is in a petri dish outside the body, are you going to really be able to tell anything meaningful about miscarriage or embryonic development?” said Marcy Darnovsky, executive director of the Center for Genetics and Society, as reported by the Associated Press.
Courthouse News reporter Cain Burdeau is based in the European Union.