Scientists Create a Human Embryo Model Without Using Sperm or Eggs | Sciences

Scientists have succeeded in developing an entity that looks like an early human embryo, without the use of sperm, eggs or a uterus.

The Weizmann Institute team claims that the ‘model embryo’, made from stem cells, looks like a perfect example of a real 14-day-old fetus.

It even released hormones that tested positive for pregnancy in a lab test.

The ambition of embryonic models is to provide an ethical way to understand the first moments of our lives.

The first few weeks after a sperm fertilizes an egg is a period of dramatic change — from an inconspicuous collection of cells to something eventually recognizable on an ultrasound.

This timing is crucial for many miscarriages and birth defects, but it is not well understood.

“It’s a black box, and that’s not a cliché – our knowledge is very limited,” says Professor Jacob Hanna, of the Weizmann Institute of Science, via video call.

Embryo research is a legal, ethical, and technically complex process. But now there is a rapidly developing field that mimics the normal development of a fetus.

The Israeli team described the research, which was published in the journal Nature, as the first “complete” embryonic model that simulates all the major structures seen in the early embryo.

“It’s actually a perfect picture of a 14-day-old human fetus, which hasn’t been done before,” says Hannah.

Instead of sperm and an egg, the starting material was immature stem cells that had been reprogrammed to gain the ability to become any type of tissue in the body.

Chemicals were then used to stimulate these stem cells to become the four types of cells found in the early stages of the human embryo:

• ectodermal cells, which become a healthy embryo (or embryo);
• trophoblast cells, which become the placenta;
• subplastic cells, which become the supporting yolk sac;
• Extraembryonic cells of the mesoderm.

A total of 120 of these cells were mixed in a minute ratio, and then the scientists stopped and watched.

About 1% of the mixture began the journey of spontaneous development into a structure resembling, but not identical to, a human embryo.

“I give the cells a lot of credit — you have to get the right mix and have the right environment, and everything happens,” says Hannah. “It’s an incredible phenomenon.”

Embryo models were able to grow and develop until they were comparable to an embryo 14 days after fertilization. In many countries, this is the legal limit for normal embryo research.

Despite my late-night video call, I can hear the excitement when Professor Jacob Hanna takes me on a 3D tour of the ‘wonderful architecture’ of the embryo model.

I can see the trophoblast, which usually becomes the placenta, surrounding the fetus. This includes cavities called lacunae that fill with the mother’s blood to transfer nutrients to the baby.

There is the yolk sac which performs some of the functions of the liver and kidneys, and the bilaminate embryonic disc – one of the main features of this stage of embryonic development.

The hope is that embryo models will help scientists explain how different types of cells arise, witness the first steps in building organs, or understand hereditary or hereditary diseases.

This study already shows that other parts of the fetus will not form unless the cells of the first placenta can surround it.

There is even talk of improving in vitro fertilization success rates, helping to understand why some embryos fail, or using models to test whether drugs are safe during pregnancy.

Professor Robin Lovell-Badge, who researches embryonic development at the Francis Crick Institute, says these embryo models “look very good” and appear to be “completely normal”.

“I think it’s a good thing, I think it’s very well executed, everything makes sense and I’m really impressed,” he says.

He adds that the current failure rate of 99 percent needs improvement. It would be hard to understand what goes wrong with miscarriage or infertility if the pattern fails to form most of the time.

This work also raises questions about whether fetal development beyond the 14-day stage can be simulated.

This would not be illegal, at least in the UK, as embryo models are legally different from embryos.

“Some people will like it, but others won’t,” says Lovell-Badge.

This is “very important research,” says Alfonso Martinez Arias, a professor at the Department of Experimental and Health Sciences at Pompeu Fabra University (Spain).

“The work has achieved, for the first time, an accurate construction of the complete structure [de um embrião humano] stem cells” in the laboratory, “which opens the door to studying the events that lead to the formation of the human body plan,” he said.

The researchers point out that it would be unethical, illegal, and indeed illegal to achieve pregnancy using these embryo models – a 120-cell construct exceeds the point at which an embryo can be successfully implanted into the cervix.