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‘Synthetic’ human embryos created without eggs or sperm by University of Cambridge scientists

University of Cambridge researchers have created “synthetic” human embryos without the need for eggs or sperm in what is a major scientific advance - and one that raises significant ethical and legal issues.

The model embryos could help in the study of disease and genetic disorders, or recurrent miscarriage.

Prof Magdalena Zernicka-Goetz Picture: Simon Zernicki-Glover
Prof Magdalena Zernicka-Goetz Picture: Simon Zernicki-Glover

But it not yet clear whether they have the potential to continue maturing beyond the earliest stages of development.

The work falls outside current UK legislation and has yet to be published in a scientific journal, or peer-reviewed.

But Prof Magdalena Zernicka-Goetz, of the University of Cambridge and the California Institute of Technology, described it last week at the International Society for Stem Cell Research’s annual meeting in Boston.

“We can create human embryo-like models by the reprogramming of (embryonic stem) cells,” she told the meeting.

The structures do not require eggs or sperm, do not have a beating heart or beginnings of a brain but do contain cells that would typically develop to form the placenta, yolk sac and the embryo itself.

It follows an extraordinary breakthrough last year by Prof Zernicka-Goetz’s lab that was the culmination of 10 years of work, in which a synthetic mouse embryo with a brain, beating heart and the foundation of all the body’s other organs was created using stem cells.

As the Cambridge Independent reported, the researchers described that success as “a dream come true” and said it could unlock the mystery of why some pregnancies fail in the early stages, enable the healing of organs and accelerate the creation of synthetic human organs for transplantation.

Following the latest advance, Prof Robin Lovell-Badge, head of the laboratory of stem cell biology and developmental genetics at the Francis Crick Institute, told BBC Radio 4’s Today programme last Thursday that the aim of the research was to try and model early human development.

“If you want to understand really what is going on as embryos develop normally, or when things go wrong earlier leading to miscarriage or some congenital disorders for example, then currently people are having to use embryos that are donated for research, which are left over after in vitro fertilisation (IVF),” he said.

“These are quite rare and hard to get, so if you could use the stem cells to model those early stages of human development, then maybe you could get a lot of information without having to resort to using embryos that have been created by fertilisation.”

A human embryo. Picture: University of Cambridge
A human embryo. Picture: University of Cambridge

He said it was unclear yet whether the models could identify reasons for miscarriage and spoke about the ethical and regulatory considerations.

“What you’re trying to do is model early human development,” he said. “So these structures that have been made so far are clearly not perfect models of human development, because they don’t go that far.

“However, the whole intention is to devise ways of making them more and more perfect models.

“And of course, then the closer you get to a human embryo, then you have to start (thinking) ‘well, what’s the difference between a normal human embryo and one of these models?’

“And so should they be governed by the same rules that are used to govern research with human embryos or not? So that’s the big sort of regulatory issue at the moment and a sort of ethical issue.”

Dr Ildem Akerman, associate professor in functional genomics at the University of Birmingham, said that “in theory, these cells also have the potential to develop into an embryo”.

She added: “This report suggests that there is now proof that human embryonic stem cells can potentially become embryos…

“We understand from the report that the scientists generated optimal conditions for the embryo to pass through the first 14 days of development and, in fact, become an embryo.

“Recently scientists developed methods to keep IVF embryos alive in a dish for 14 days, and these findings confirm that the technology is now available to mimic the first 14 days of development outside the womb.”

She said the work has “significant implications” and “will provide scientists with a model to investigate the events that occur during the initial 14 days of life”.

She added: “Up until now, we have only been able to observe such processes in animal models like zebrafish and mice.

“Having this knowledge can be immensely valuable for regenerative medicine, where scientists aim to generate different cell types from stem cells (such as pancreatic beta cells for people living with type 1 diabetes).

“It can give us valuable insights into genetic disorders. Additionally, it can contribute to the advancement of IVF technologies.”

She said that although the scientists had referred to “synthetic” embryos, “these cell clusters are not truly synthetic in the sense that they are created from scratch”.

She said: “Instead, they are derived from living stem cells that originate from an embryo.

“Essentially, what scientists do is cultivate a single stem cell and encourage its growth into an organised group of cells that, in theory, possess the potential to develop into an implantable embryo.”

Professor Roger Sturmey, a senior research fellow in maternal and foetal health at the University of Manchester, said there is still much work to do “to determine the similarities and differences between synthetic embryos and embryos that form from the union of an egg and a sperm”.

He said the new work has not yet been “fully appraised by the scientific community, but it does offer exciting prospects to answer these questions and may provide an important tool to study early development while reducing the reliance on human embryos for such research”.

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