A research team in the UK and US has created “synthetic” mouse embryos to develop brains, nerves and beating heart tissue in the lab, without needing a fertilized egg or a uterus to develop.
It is similar to a breakthrough by a group of Israelis, announced earlier this month. Together, the breakthroughs promise to revolutionize the understanding of one of biology’s greatest challenges: how some cells continue to organize themselves into life.
If applied to human embryos, the study could help to better understand human fertility and developmental disorders and provide a new avenue for developing tissues or organs for transplantation in the future. laboratory.
But applying this technique to human embryos will enhance Important ethical and legal questions.
“The big question we’re dealing with in the lab is how do we start our lives?” Professor Magdalena Zernicka-Goetz from Caltech in Pasadena, California and the University of Cambridge in the UK said.
To create synthetic embryos, or “embryos,” scientists took three types of stem cells from mouse embryos that would normally go on to form all the necessary tissues in a developing embryo. .
They then transferred the cells into an artificial growth medium – essentially a rotating vessel filled with nutrients.
Stem cells continue to form embryos naturally.
Professor Zernicka-Goetz said: “Only about 1 in 100 people succeed, but a small number of cases are “completely indistinguishable from natural embryos”.
The embryos develop in only eight and a half days, which is about half the normal gestation period of mice.
But the technique must still be extremely important as a way to generate early embryos to study early development without the need for laboratory animals.
The team is currently actively working on a model of a human embryo, but emphasizes that there is still a way to go. There are significant differences between early mouse development and human development.
But obtaining a synthetic human embryo could be a big step forward for the study of fertility and common developmental disorders.
“The vast majority of human pregnancies are lost early in our lives, and IVF fails in 20 to 70 percent of cases,” said Professor Zernicka-Goetz.
The supply of donated human embryos is scarce and often of poor quality, so lab-grown “model” embryos can help answer many questions.
The team is proposing synthetic embryos that reproduce only one element of the original human embryo, such as the heart, or a model of the placenta during implantation. Implantation failure is a major reason for IVF failure.
Synthetic human embryos could also be a way to create new tissues or organs for “regenerative” medicine. If taken from the patient’s own stem cells, such tissues could be a perfect match for the recipient.
However, at least in the UK, developing synthetic human embryos would require a change in existing law that does not include embryos developing from stem cells.
UK law also prohibits culturing human embryos in the lab for the past 14 days. This occurred earlier than most of the important developmental processes seen in these mouse embryos.
Experts say this latest protest means that discussion of these legal and ethical questions should start sooner rather than later.
“The results herald that, in the future, similar experiments will be done with human cells and, at some point, will yield similar results,” said Professor Alfonso Martinez Arias of Pompeu Fabra University. in Barcelona, said people not involved in the study. .
He added: “This will encourage consideration of the ethics and social impact of these experiments before they happen.