Scientists grow human embryo without sperm or egg for the first time: “Amazing phenomenon” | Science

The team at the Weizmann Institute of Science in Israel have created an “embryo model” using stem cells. The creation closely resembles a 14-day-old human embryo, with the fetus even producing hormones that led to a positive pregnancy test.

With these developments, scientists are trying, in an ethical way, to understand the earliest moments of human life.

The first few weeks after a sperm cell has fertilized an egg cell, many changes occur: from a collection of unclear cells to something that eventually becomes recognizable to us on an ultrasound.

While these changes are crucial to understanding why miscarriages and birth defects may occur, very little is known about them in the scientific community.

“Our knowledge about these changes in early pregnancy is very limited,” says Professor Jacob Hanna of the Weizmann Institute of Science.

This research is described by the team of scientists as the first “complete” embryo model that mimics all major structures in the early stages.

“This is really a textbook example of what a human embryo looks like on day 14 and that has never been done before,” Hanna continues.

Instead of a sperm cell and an egg cell, stem cells were the basic material. These cells were reprogrammed to give them the power to potentially become any type of tissue in the body.

Subsequently, chemicals were used to transform these stem cells into four cell types that occur in the earliest stage of the human embryo.

About one percent of the mixture spontaneously began to assemble into a structure similar to, but not identical to, a human embryo.

“The cells are extremely important. You have to have the right mix and the right conditions to get to this composition,” says Hanna. “When that happens, it’s an amazing phenomenon.”

The embryo models were allowed to grow and develop until they were comparable to a 14-day post-fertilization embryo. In many countries this is the legal limit for embryo research.

Scientists hope that these embryo models help explain how different types of cells form and exactly how this works during the building of the body’s organs. In addition, these models could provide more insight into hereditary or genetic diseases.

Gaining more clarity about this crucial stage, they say, could improve in vitro fertilization (IVF) success rates by helping scientists better understand why some embryos fail. In addition, these models can also be useful for testing what exactly drugs do to a pregnant woman.

Whether you can simulate an effective pregnancy with these embryo models is not clear. “It would be unethical, illegal and basically impossible to achieve a pregnancy,” scientists emphasize.