Rivron’s lab was the first to create these embryo-like structures in 2018. His team showed that mouse stem cells can self-organize into blastocyst-like structures, which form five or six days after sperm fertilizes an egg. They called the balls of cells “blastoids”.
Then in 2021, several labs showed that they could create human blast cells using stem cells. And last year, researchers at the University of Cambridge and Caltech reported that they had created rat structures that mimicked normal embryos at 8.5 days of development, which contained beating hearts and neural folds, the foundations of the brain.
The scientists behind these experiments insist that these balls of cells are just models, not actual embryos. The International Society for Stem Cell Research, or ISSCR, a scientific group that sets guidelines for stem cell research, prohibits the transfer of these structures to humans for the purpose of attempting to initiate a pregnancy.
For now, scientists want to use them to better understand early pregnancy. “Since apes are evolutionarily closely related to humans, we hope that studying these models will deepen our understanding of human embryonic development, including shedding light on some of the causes of early miscarriage,” said Chen Liu of the Chinese Academy of Sciences in Shanghai. , one of the study’s authors, in a news release. (Liu’s team did not respond to an emailed request for comment by press time.)
However, trying this on a monkey is the closest approximation to what would happen in a human. “This shows that you can initiate a pregnancy, or at least trigger a macaque’s hormonal system to think she’s pregnant,” says Hank Greeley, MD, director of the Center for Law and Biological Sciences at Stanford University School of Medicine. “She says there’s some evidence that maybe it can trigger a baby monkey.”
Embryo research is particularly controversial in the United States, where it has faced religious objections for decades. While most states allow research on human embryos, national law prohibits the use of federal funds in their creation or destruction.
Several countries, including the UK, Canada and South Korea, have legal restrictions against growing human embryos in vitro beyond 14 days after fertilization – when the first signs of the central nervous system appear. (In other countries, the 14-day rule is just a guideline, initially set by the ISSCR.) In 2021, the ISSCR relaxed the 14-day rule to consider experiments involving human fetuses developing past this mark on a case-by-case basis. case basis.
Embryo models give researchers an alternative without having to rely on the real thing. But as they develop further, they raise their own concerns. “I think what we’d really like to know is: Can an embryonic model lead to a living organism?” Greeley says. “If it is possible, then it should be treated like a fetus. If you cannot, then you need not be treated like a fetus.”
To answer that question, Greeley advocates for scientists conducting the kind of experiments the new paper outlines. He feels it would be unethical to do this to people, because any resulting children could end up with birth defects or genetic disorders.
Riverron believes that scientists should move slowly in trying to prove animal pregnancy using blastula, because it is very likely that these structures will not develop properly. But with the current pace of research in this area, it is believed that the first living mouse born from a blastoid could become a reality within five years. “I think we have to do things incrementally to make sure we do it right.”
In their press release, the team behind the new paper recognized the work could be controversial. “The researchers said they acknowledge the ethical concerns surrounding this type of research, but stress that there are still many differences between these embryo-like structures and normal blastocysts,” the statement reads. “Importantly, embryo-like structures do not possess full developmental potential. In order to make progress in this area, it is important to have discussions between the scientific community and the public,” they noted.