This week, during The Global Stem Cell Event in Boston, Mass., scientists revealed that they have created a synthetic human embryo without an egg or sperm.
It isn’t clear yet whether these embryos could eventually mature into living, breathing, humans. However, their mere existence is “groundbreaking,” according to The Guardian, the first outlet to report on the discovery.
Details of this research has not yet been published.
Instead of egg and sperm, Magdalena Żernicka-Goetz, of the University of Cambridge and the California Institute of Technology and other researchers used stem cells to create the model embryos.
“We can create human embryo-like models by the reprogramming of [embryonic stem] cells,” Żernicka-Goetz explained during the meeting. Previously, she worked on a project that found stem cells from mice could be encouraged to self-assemble into early embryo-like structures with an intestinal tract, the beginnings of a brain and a beating heart.
Embryo models discussed this week resemble embryos in the earliest stages of human development, when pregnancies often fail. Scientists hope that the synthetic embryos – which do not have a beating heart or the beginnings of a brain, but include cells that would typically go on to form the placenta, yolk sac and more – will help them understand why miscarriages happen.
“The motivation for the work is for scientists to understand the ‘black box’ period of development that is so called because scientists are only allowed to cultivate embryos in the lab up to a legal limit of 14 days,” said The Guardian. “They then pick up the course of development much further along by looking at pregnancy scans and embryos donated for research.”
During the conference, which runs through Saturday, Żernicka-Goetz discussed the model embryos being cultivated to a stage just beyond the equivalent of 14 days of development for a natural embryo.
“It’s beautiful and created entirely from embryonic stem cells,” Żernicka-Goetz told the Guardian before the talk.
Models grown from a single embryonic stem cell reached the beginning of a developmental milestone known as gastrulation. Per the National Institutes of Health, this is “an early developmental process in which an embryo transforms from a one-dimensional layer of epithelial cells, a blastula, and reorganizes into a multilayered and multidimensional structure called the gastrula.”
According to the Żernicka-Goetz lab website, knowledge of embryo development has “allowed us to create the first synthetic embryos through assembly of different stem cell types – embryonic and extra-embryonic stem cells – that assemble into structures that recapitulate natural spatially regulated gene expression and morphogenesis to undertake gastrulation and develop to neurulation.”
However, Żernicka-Goetz told CNN that she wished to “stress that they are not human embryos,” but models of them.
“There is no near-term prospect of the synthetic embryos being used clinically,” said the Guardian. “It would be illegal to implant them into a patient’s womb, and it is not yet clear whether these structures have the potential to continue maturing beyond the earliest stages of development.”
Even so, the new research has raised legal and ethical questions, said the outlet.
“If the whole intention is that these models are very much like normal embryos, then in a way they should be treated the same,” said Robin Lovell-Badge, the head of stem cell biology and developmental genetics at the Francis Crick Institute in London “Currently in legislation they’re not. People are worried about this.”
Previously, embryos grown from mouse cells reported to appear almost identical to natural embryos didn’t develop when implanted into mice wombs. Similarly, when researchers in China created synthetic embryos from monkey cells and implanted them into the wombs of adult monkeys, none developed further than a few days.
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