World’s first ‘synthetic embryo' is already causing controversy

Breakthroughs happen when scientific explorations meet medical experiments. Researchers at the Weizmann Institute in Israel have produced the world's first "synthetic embryos" without the need for sperm, eggs or fertilization.

Scientists grew "synthetic embryos" from mouse cells after discovering that it was possible to make mouse stem cells self-assemble into structures that resembled early embryos that have a developing intestinal tract, brain and heart. beats.

Published in the journal Cell by a team led by researchers at the Weizmann Institute of Science in Israel, is a very sophisticated model of what happens during the early development of the mouse embryo, immediately after implantation.

This is a crucial stage for pregnancy, as many human pregnancies are lost during this stage. If trials to develop a human embryo without using sperm or eggs, they may negate the need for sperm or egg donors for ART and advance reproductive medical practices.

"Surprisingly, we show that embryonic stem cells generate whole synthetic embryos, meaning this includes the placenta and the yolk sac that surrounds the embryo," said Professor Jacob Hanna, who led the effort. “We are really excited about this work and its implications.” The work is published in Cell.

Last year, the same team described how they had built a mechanical womb that allowed natural mouse embryos to grow outside the womb for several days. In the latest work, the same device was used to nurture mouse stem cells for more than a week, almost half the gestation time of a mouse.

Some of the cells were previously treated with chemicals, which activated genetic programs to become the placenta or yolk sac, while others developed without intervention into organs and other tissues.

While most of the stem cells failed to form embryo-like structures, about 0.5% combined into small balls that developed into various tissues and organs. Compared to natural mouse embryos, the synthetic embryos were 95% the same in terms of their internal structure and the genetic profiles of the cells. As far as the scientists could tell, the organs that formed were functional.

Hanna said that the synthetic embryos were not "real" embryos and did not have the potential to become living animals, or at least when they were transplanted into the wombs of female mice. He has founded a company called Renewal Bio that aims to grow synthetic human embryos to provide tissues and cells for medical conditions.

Why has it sparked an ethical controversy?

No embryonic model can occur without a source of stem cells, so when it comes to thinking about the future use of this technology, it is vital to ask: where do these cells come from? Are they human embryonic stem cells (derived from a blastocyst) or are they induced pluripotent stem cells?

The latter can be made in the laboratory from skin or blood cells, for example, or even derived from frozen samples.

An important consideration is whether the use of cells for this particular type of research (trying to mimic an embryo in a dish) requires any specific consent.

Although such embryos have been developed for mice, it has generated much debate about what it could mean for human reproduction. The cloning of human embryos has various ethical concerns when it comes to the laws of different countries, but scientists have not yet made any announcements about reaching the stage of testing in humans.

Synthetic embryo creation process

Initially, the group of researchers managed to grow mouse embryos outside the womb, in glass containers that were taken directly from real mice and fertilized. In follow-up experiments, embryos were grown from stem cells.

The researchers attempted to emulate what an embryo does, building on two previous advances including an efficient method of reprogramming stem cells to a naive state and using an electronically controlled device that keeps embryos bathed in a nutrient solution inside vessels of continuously moving precipitates. , simulating the way nutrients are supplied by material blood flow to the placenta.

For the first step, which lasted about two days, the researchers started with several-day-old mouse embryos just after they had implanted in the uterus.

Synthetic Embryo Culture Organs

Some of the cells were previously treated with chemicals, which activated genetic programs to become the placenta or yolk sac, while others developed without intervention into organs and other tissues.

Most of the stem cells failed to form embryo-like structures, yet about 0.5% combined into small balls that developed into various tissues and organs. Compared to natural mouse embryos, the synthetic embryos were 95% the same in terms of their internal structure and the genetic profiles of the cells. The scientists observed that the organs that formed were functional.

The itch of science! Scientists say the next challenge is to understand how stem cells know what to do and how they self-assemble into organs and find their way to their assigned places within an embryo.

According to the researchers, this breakthrough may also decrease the use of animals in experiments and could eventually open up space for new supplies of cells and tissues for use in human transplants. "Now is a good time to consider the best legal and ethical framework to regulate the research and use of synthetic human embryos and update current regulations," one of the scientists behind this research said according to some press reports.

We are still a long way from growing human embryos from stem cells. The synthetic mouse embryos developed by this team were not able to develop into a living mouse, and much less is still known about human embryos. On the plus side, this innovation jump-starts this field of research and with this, scientists will one day be able to generate an embryo from scratch and potentially a living organism.

Speaking to StatNews, Professor Paul Tesar, a geneticist at Case Western Reserve University, said that the more scientists push stem cell-derived embryos further and further down the developmental path, the more synthetic and natural embryos begin to merge.

"There will always be a gray area," he said. "But as scientists and as a society we must come together to decide where the line is and define what is ethically acceptable."

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