Reengineering Life

Scientists Can Now Grow ‘Synthetic’ Early Human Embryos in a Dish

The research reignites a debate over embryo research

Emily Mullin
Future Human
Published in
5 min readMar 17, 2021
Photo illustration. Image credit: Monash University

Reengineering Life is a column from Future Human about the ways humans are using biology to reprogram our bodies and the world around us.

Under a microscope, the little balls of cells look like five-day-old human embryos, known as blastocysts. They’re similar in size, shape, and structure. They even have the three distinct cell types that exist in real blastocysts — the kind that forms the embryo itself, another that makes the placenta, and a third type that gives rise to the sac in which the embryo will develop.

But there’s one key difference between these embryo look-alikes and natural ones: They weren’t made with human eggs and sperm.

In two papers published March 17 in the journal Nature, researchers report that they created living structures that resemble early embryos using human skin cells and stem cells. Scientists have previously made “synthetic” mouse embryos and even used them to grow a mouse fetus. And last year, scientists described making versions of later-stage human embryos. These, however, mimic an embryo at an even earlier stage and are among the most complete models of a human embryo to date.

Currently, scientists who study early human development must rely on difficult-to-obtain embryos donated from patients undergoing fertility treatments at in vitro fertilization clinics. These new models could provide a way to investigate how healthy embryos form without the use of actual embryos. Scientists say these embryo-like structures will help them better study the causes of birth defects and genetic diseases, as well as the impact of chemicals, toxins, and viruses on early embryos.

“They will allow us to study now, at scale, the very early steps of human development without having to use blastocysts donated from IVF,” said José Polo, PhD, a developmental biologist at Monash University in Australia and lead author of one of the papers, in a March 16 call with reporters.

In one paper, Polo and his team made the embryo-like structures by converting human skin cells into an intermediate type of stem cell. In…



Emily Mullin
Future Human

Former staff writer at Medium, where I covered biotech, genetics, and Covid-19 for OneZero, Future Human, Elemental, and the Coronavirus Blog.