Scientists have generated early-stage models of human embryos that could help shed light on the “black box” of the early stages of human development and improve research on pregnancy loss and birth defects.
Two separate teams have found different ways to produce versions of a blastocyst – the stage of development about five days after a sperm fertilizes an egg – that could open the door for a huge expansion of research.
Scientists clearly show that the models differ from human blastocysts and are not able to develop into embryos. But their work comes as new ethical guidelines are developed for such research and could spark new debate.
The teams, whose research was published in the journal on Wednesday The nature, I believe that the models called “blastoids” will help research in any case, from miscarriages to the effects of toxins and drugs on early-stage embryos.
“We are very excited,” said Jun Wu of the University of Texas Southwestern Medical Center, who led one of the teams.
“Studying human development is really difficult, especially at this stage of development, it is essentially a black box,” he said in a press briefing before publishing the research.
At this time, research in the early days of embryonic development is based on blastocysts donated from IVF treatment.
But the offer is limited, subject to restrictions and is only available for certain research facilities.
So the ability to generate unlimited models could change the game, said Jose Polo, a professor at Monash University in Australia who led the second research team.
“We believe that this ability to work at scale will revolutionize our understanding of the early stages of human development,” he told reporters.
The generation of blastocyst models has so far been done only in animals, the researchers in 2018 successfully generating them in mice using stem cells.
The two teams approached the development of a human model in slightly different ways.
Wu’s team used two different types of stem cells, some derived from human embryos and others so-called induced pluripotent cells produced from adult cells.
Polo’s team instead started with adult skin cells, but both teams actually came to the same result: the cells began to organize into blastoids, presenting the three key components seen in a human blastocyst.
“For us, what was completely surprising was that when you put them together, they organize themselves, they seem to talk to each other in a way … and they strengthen,” Polo said.
But, although the patterns are similar to human blastocysts in many ways, there are also significant differences.
The blastocysts of both teams have come to contain cells of unknown types and they lack some elements that come specifically from the interaction between sperm and egg.
Blastoids have worked on average about 20% of the time, although teams say they are still a path to a significant supply of research.
Ethical debate
Scientists are trying to make it clear that models should not be seen as pseudo-embryos and are not able to develop in the fetus.
However, they proceeded with caution, choosing to complete the blastoid research four days after culturing, equivalent to about 10 days after fertilization in a normal sperm-egg interaction.
Research rules involving human blastocysts have set this deadline at 14 days.
Peter Rugg-Gunn, group leader at the Babraham Institute for Life Sciences Research in the UK, said the processes were “interesting progress”.
But Rugg-Gunn, who was not involved in the research, said work was needed to improve the comparatively low success rate of blastoid generation.
“To capitalize on the discovery, the process will need to be more controlled and less variable,” he said.
And given the differences between human blastoids and blastocysts, the models offer the opportunity to help, but not replace research on donations, said Teresa Rayon of the Francis Crick Institute, a biomedical research center.
These “may help generate hypotheses that will need to be validated in human embryos,” she said.
Research may also trigger ethical debates, said Yi Zheng and Jianping Fu of the University of Michigan’s mechanical engineering department.
Some “might view human blastoid research as a pathway to human embryo engineering,” they wrote in an article accompanying studies in The nature.
The research “calls for public conversations about the scientific significance of this research, as well as about the social and ethical issues it raises.”
© Agence France-Presse