Scientists Create ‘Synthetic Embryos’ From Monkey Cells

For the first time, scientists have used monkey cells to created embryo-like structures—without using a sperm, egg or uterus, according to a paper recently published in the journal Cell Stem Cell. And in another first, they implanted those structures in live monkeys. The effort could open avenues for research without the ethical issues of experimenting on real human embryos.

A embryo in vivo, or developing inside an organism, is very difficult for scientists to observe—in its early days, the ball of cells attaches to the wall of the uterus and essentially disappears, writes Wired’s Emily Mullin. But with “synthetic” embryos grown in a lab, researchers hope to get a better view of embryo development and look for the causes of some birth defects and miscarriages.

“The work highlights the amazing potential of stem-cell-based embryo models as a means to explore embryonic stages that are typically difficult to access in vivo,” Naomi Moris, a developmental biologist at the Francis Crick Institute in England who did not participate in the research, tells Nature News’ Gemma Conroy.

Instead of creating an embryo from a sperm and egg, the effort uses stem cells, which can develop into many different types of cells, to create embryo-like structures in a lab. It’s not the first study to do so—researchers have done similar work with stem cells from humans and from mice.

This time, the scientists used cells from cynomolgus macaques, a species of monkey that is biologically similar to humans. The team began with embryonic stem cells that had been grown in a lab for multiple generations, then coaxed them to develop. The resulting structures resembled blastocysts, or clusters of cells in the early stages of an embryo’s development, and for this resemblance, they’re known as blastoids.

The lab-grown blastoids took on the same spherical structure as natural blastocysts. They even developed into three key layers of cells that eventually give rise to the body’s tissues and organs. And the blastoids could survive in the lab for about 18 days.

“The findings are a milestone in the field of stem cell-derived embryo models,” Alejandro De Los Angeles, a stem cell biologist at the University of Oxford in England who wasn’t involved in the research, tells Science’s Mitch Leslie.

But then, the scientists took things a step further: Seven days into their development, eight to ten blastoids were surgically placed into each of the uteruses of eight adult monkeys. Following the surgery, three of the monkeys showed signs of pregnancy—they developed gestation sacs for seven to ten days and released pregnancy hormones, per Nature News.

However, these indicators disappeared after 20 days. This shows that the blastoids aren’t exactly the same as normal embryos, Alfonso Martinez Arias, a developmental biologist at Pompeu Fabra University in Spain who didn’t contribute to the research, tells MIT Technology Review’s Jessica Hamzelou.

Still, the work is “amazing,” Susana Chuva de Sousa Lopes, a developmental biologist at Leiden University in the Netherlands who did not contribute to the study, tells the publication. “It’s the first time I’ve seen [synthetic embryos] developed so far, and with such good quality.”

Apart from the recent study, other teams of researchers also developed synthetic embryos from monkey stem cells—and in two papers published in May, they describe how the embryos survived for 25 days in vials in the lab. Nature News reports that these are likely to be the oldest-ever primate embryos grown outside of a living creature.

The scientific community is still sorting out the ethics of this type of research. Nicolas Rivron, an embryologist at the Austrian Academy of Sciences, tells Wired that pregnancies from blastoids would likely not develop correctly, so scientists should proceed carefully with initiating pregnancies from stem cells.

“We’re definitely moving very fast, and developments are being made really, really rapidly in this field,” Moris says to MIT Technology Review. Laws need to keep pace with scientific advancements “to make sure we’re not pushing ahead too fast,” she tells the publication.

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Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.