Researchers Create First Synthetic Human Embryo

An egg plus sperm equals a human embryo—at least that's traditionally how it's been done. In a breakthrough, scientists say they've created human embryos without the need for either egg or sperm. These "synthetic embryos" or "embryo models" are made from reprogrammed embryonic stem cells. But they resemble true embryos with "cells that would typically go on to form the placenta, yolk sac and the embryo itself," per the Guardian. As Dr. Magdalena Zernicka-Goetz, a professor of biology at CalTech and Cambridge University, tells the outlet, "our human model is the first three-lineage human embryo model that specifies amnion and germ cells, precursor cells of egg and sperm."

However, "it is not yet clear whether these structures have the potential to continue maturing beyond the earliest stages of development," per the Guardian. Zernicka-Goetz has previously developed synthetic mouse embryos "with evidence of a developing brain and beating heart," per the outlet, but these failed to develop when implanted into the wombs of female mice. Synthetic embryos implanted into monkeys also failed to develop. Zernicka-Goetz, who described her research Wednesday at the annual meeting of the International Society for Stem Cell Research in Boston, only spoke of cultivating the human embryo models just past the stage of development that a natural embryo would reach in 14 days.

As the BBC notes, most countries cut off human-embryo research after 14 days. A host of ethical issues are raised, however, as synthetic human embryos don't fall under current law, though there are calls for that to change. While "nobody is currently suggesting growing them into a baby," per the BBC—indeed, it would be illegal to do so—researchers do hope they can be used to better understand genetic diseases and miscarriage in early pregnancy. So similar to human embryos, they present a "very important path towards discovery of why so many pregnancies fail," Zernicka-Goetz tells CNN, noting the majority of miscarriages occur "around the time of the development at which we build these embryo-like structures." (More embryo stories.)