Scientists have created embryo models to help study the mysteries of early human development, the medical problems that can occur before birth and why many pregnancies fail.
These models are made from stem cells, not eggs and sperm, and cannot grow and develop into babies.
“They’re complete enough to give you a picture of what’s happening in the fetus during pregnancy, but they’re not complete enough that you can really use them for reproduction,” says Insu, ethologist and director of life sciences. Hyun said at Boston’s Museum of Science. “It will not work.”
The use of models also avoids the controversy surrounding the use of real embryos in research, he said.
Several groups are working on the research. Teams of researchers from the United States and England shared their work in two studies published Tuesday in the journal Nature. Other scientists from Israel and China published the study earlier this month on their work which has not yet been peer-reviewed.
While previous models mimicked a pre-embryo, Hyun said the latest models model an embryo after it has implanted in the uterus. At that stage it can be extremely difficult to see actual human embryos because they are embedded in the uterus. Each team’s models differ in the techniques used and how complete they are, he said, with some showing not only the embryo but also the placenta and the beginnings of the yolk sac.
For this type of model, scientists use a type of stem cell that is capable of developing into many different types of cells or tissues in the body. They can be from embryos or can be reprogrammed from adult tissues.
The authors of a Nature paper describe models that resemble human embryos nine to 14 days after fertilization.
“If we can experimentally model this period, we can finally begin to ask questions about how human development occurs in those early stages that are normally hidden within the mother’s body,” said study author Berna. said Sozen, who studies developmental stem cell biology at Yale University.
Scientists will also be able to study fetal failure, developmental disorders and pregnancy loss, Sozen said. At this point, we don’t understand how it goes awry, he said.
In the other Nature paper, Magdalena Zernica-Goetz, an expert in stem cell biology at the California Institute of Technology and the University of Cambridge in England, and colleagues said their model reflects development up to 14 days from fertilization. That model includes embryonic tissue and tissues that can form structures such as the placenta and yolk sac surrounding the embryo.
Jacob Hanna of the Weizmann Institute of Science in Israel, author of the yet-to-be-reviewed paper, said in an email that his group’s model also reflects human embryonic development up to day 14 after fertilization. He said the structures included all embryonic membranes as well as membranes outside the embryo.
Both Hanna and Zernicka-Goetz had previously helped create the mouse embryo model.
Zernicka-Goetz said the human embryo model could be used to explore the effects of the environment and chemicals on early development. They could also be used to generate tissues to be used in new medical treatments, he added.
Sozen also envisions testing drugs on fetal models and exposing them to microbes—experiments that can’t be done on pregnant people.
Guidelines from the International Society for Stem Cell Research state that scientists may not insert any human embryo model into a human or non-human uterus. For decades, the society had a concerning “14-day rule” that guided researchers as to how long real embryos could be grown in the lab — which the group recommended relaxing in 2021 under limited circumstances. But because models are not fetuses, they’re not subject to the rule.
Experts said some people in the public have a misconception about these models, believing they may be able to conceive. But scientific constraints prevent this. For example, they do not develop a proper placenta. Hyun, who is also a member of Harvard Medical School’s Center for Bioethics, said that even in the future, as the field progresses, there are ways to guard against bad actors who want to try to conceive from embryo models. .
The moral reason not to make them perfect, he said, is that “the whole purpose of these models is to avoid embryo controversy.”
,
AP video journalist Howovy Todd contributed from London.
,
The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute’s Science and Educational Media Group. AP is solely responsible for all content.
