Scientists create a typical human embryo without sperm or egg

Scientists built a model of the fetus, shown here. The outer ring is what forms the placenta.
Weizmann Institute of Science

  • Scientists used stem cells to create a model of an embryo in the laboratory without sperm or eggs.
  • A typical fetus releases the same hormones that lead to positive pregnancy tests.
  • Researchers hope to use this model to understand early development, miscarriage and genetic diseases.

We know a lot about how babies are born, but not everything. Surprisingly, scientists understand little about the first days of fetal development, when our cells organize and begin to form our bodies.

Researchers have brought us a step closer to understanding those early days by creating a model of a human embryo in the laboratory, without the use of sperm or eggs. They published their findings in the journal Nature.

“The drama happens in the first month, and the remaining eight months of pregnancy are basically a lot of growth,” Jacob Hanna, a co-author of the study who researches molecular genetics at the Weizmann Institute of Science, said in an institutional press release.

Most miscarriages occur during the first 11 weeks of pregnancy, according to the Mayo Clinic. These models can help scientists understand what errors can occur early in these developmental stages in order to try to prevent them, Hanna said in the press release.

He also said the models could be used to determine how genetic diseases as well as birth defects develop.

How were scientists able to grow a typical human embryo without sperm or egg?

In order to achieve this feat, the team turned to stem cells. Stem cells are cells that form other, more complex types of cells depending on the messages the body sends to them. The Mayo Clinic calls it “the body’s raw materials.”

Starting with stem cells, the researchers transformed them into the types of cells that make up the human embryo, from the placenta to the fetus. They then mixed these cell types together and left them alone.

Magically, as if guided by a tiny magnet, some cell types organized themselves within their dishes into configurations you might see in a human embryo.

“I give the cells a lot of credit,” Hanna told the BBC. “You have to get the right mix and have the right environment and they will take off.” “This is an amazing phenomenon.”

This is the 14-day stage in which a typical embryo develops. The researchers say this closely mimics what a real human fetus looks like after 14 days.
Weizmann Institute of Science

Supported by laboratory conditions, the researchers allowed the cells to grow for 14 days, the legal limit for embryo research in many countries.

The mass mimicked a real fetus so effectively that it resulted in a positive pregnancy test, according to the press release.

The BBC reported that scientists do not aim to place any of these false embryos into humans.

In addition to better understanding miscarriages, genetic diseases and birth defects, researchers aim to use these embryo models to conduct experiments that wouldn’t be possible with real human embryos, such as learning which medications are safe during pregnancy.

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