Scientists create synthetic human embryos from stem cells, without an egg or sperm

Team at UK’s University of Cambridge grow embryo to point where distinct cell lines form, though not brain or heart

Illustrative:  A researcher examines human embryonic stem cells with a microscope in Michigan, October 22, 2008.  (Paul Sancya/AP)
Illustrative: A researcher examines human embryonic stem cells with a microscope in Michigan, October 22, 2008. (Paul Sancya/AP)

In a groundbreaking development, scientists have created synthetic human embryos from stem cells, without using sperm or eggs.

The advance was described by Prof. Magdalena Żernicka-Goetz, of the University of Cambridge and the California Institute of Technology, during an address at the annual meeting of the International Society for Stem Cell Research, held in Boston, the Guardian reported Wednesday.

“We can create human embryo-like models by the reprogramming of cells,” Żernicka-Goetz said.

The work has yet to be published in a journal.

Previously, scientists at Israel’s Weizmann Institute, as well as Żernicka-Goetz’s team, both managed to grow stem cells from mice into embryo-like structures with a beating heart, the beginnings of a brain, and intestinal tract. The teams have since then raced to achieve the same results with human cells.

Such embryos have value in that they offer scientists a method of observing an early period of development that is currently hidden from view due to restrictions on using natural embryos. Under international regulations, scientists are only permitted to cultivate natural embryos in a lab up to 14 days. After that they can only observe development from much later pregnancy scans.

The synthetic embryos were developed to a point just beyond the equivalent of the 14-day limit, Żernicka-Goetz said. They each reached a point known as gastrulation, when the embryo begins to form distinct cells lines, according to the report. At that point, the embryos do not yet have a beating heart or the start of a brain.

“Our human model is the first three-lineage human embryo model that specifies amnion and germ cells, precursor cells of egg and sperm,” Żernicka-Goetz told the Guardian ahead of her speech at the conference. “It’s beautiful and created entirely from embryonic stem cells.”

It is not clear if the embryos can even develop into a fetus if implanted into a human womb. Other experiments in various labs around the world using similar synthetic embryos of animals did not advance beyond an earlier stage, with the reason for the natural termination not clear.

In 2021, the International Society for Stem Cell Research, a US-based non-profit organization that aims to lay down guidelines for research in the field, said the 14-day limit on developing embryos in a laboratory could be lifted under specific circumstances when there is no alternative to the research, the experiment is deemed scientifically justifiable, and if local laws and public support permit it.

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