In a groundbreaking advance, scientists created synthetic human embryos by using stem cells and without the need for eggs or sperm. The model embryos don’t have a beating heart or the beginnings of a brain, but researchers say the cells could develop to form the placenta, yolk sac, and even the embryo itself.
This breakthrough could shed light on genetic disorders and the biological causes of recurrent miscarriage, says The Guardian. However, the work is causing concern over ethical issues with synthetic embryos grown in a laboratory setting. For years, scientists have been prohibited from keeping human embryos alive in their labs for more than 14 days to avoid a thicket of ethical issues that would be raised by doing experiments on living human embryos as they continue to develop.
But according to NPR, the International Society for Stem Cell Research (ISSCR) released new guidelines in 2021 that said it could be permissible to study living human embryos in the lab for longer than two weeks. However, most institutions are sticking to the two-week rule to understand the “black box” of embryonic development, the period before pregnancy scans and donated embryos can be examined.
Magdalena Zernicka-Goetz, of the University of Cambridge and the California Institute of Technology, addressed the ISSCR’s annual meeting in Boston on Wednesday about the scientific development.
“We can create human embryo-like models by the reprogramming of (embryonic stem) cells,” she said. Experts say there is no clear clinical use for these synthetic embryos as it would be illegal to implant them into a patient’s womb and it is not clear how much farther they will develop over time.
Robin Lovell-Badge, head of the Stem Cell Biology and Developmental Genetics Laboratory at the Francis Crick Institute in London, said: “The idea is that if you really model normal human embryonic development using stem cells, you can gain an awful lot of information about how we begin development, what can go wrong, without having to use early embryos for research.”
Zernicka-Goetz described her research at the annual meeting saying that the model structures, each grown from a single embryonic stem cell, reached the stage of gastrulation. This is a stage of embryonic development in which the blastula — essentially a hollow ball or sheet of cells—is reorganized to form the gastrula, which contains the basic plan of the future organism. At this stage, the embryo doesn’t have a beating heart, gut, or beginnings of a brain, but contains the presence of primordial cells that are the precursors of egg and sperm cells, according to The Guardian.
“It’s beautiful and entirely created from embryonic stem cells,” said Zernicka-Goetz. Ideally, these structures should go on to develop into living creatures, but past research has found that it doesn’t work that way. Synthetic embryos of mice cells when implanted into the wombs of female mice didn’t develop into live animals. Chinese researchers last April implanted synthetic embryos from monkey cells into the wombs of adult monkeys. A few animals showed initial signs of pregnancy that lasted only a few days.
Lovell-Badge said it is difficult to know if the problem is technical or intrinsic to the synthetically created embryos, but it is a hurdle that needs to be overcome before the research and legislation on synthetic embryos progresses.