Synthetic embryo is such a term that has a rather daunting effect. A Chinese research group has grown such artificial embryos from monkey stem cells, allowed them to grow in the laboratory for a few days and transplanted them into the wombs of female cynomolgus monkeys. The team led by neuroscientist Zhen Liu from the Chinese Academy of Sciences (CAS) in Shanghai was able to detect hormonal signs of early pregnancy in three out of eight female monkeys. However, the cell constructs called embryoids did not develop further in the womb, but disappeared within a few days.
For experts who were not involved in the work, this does not mean that a milestone in reproductive research has been reached. Today, it cannot be ruled out “that embryoids have fundamental differences compared to real embryos that stand in the way of complete development into a viable organism,” says Rüdiger Behr, head of the research platform for degenerative diseases at the German Primate Center in Göttingen.
“It’s a lot more complicated to make artificial monkey embryos.”
Last summer, two research groups made progress with artificial mouse embryos. In the embryoids grown from mouse stem cells, the heart began to beat and other organs began to develop. The work at that time was unanimously described by experts as a breakthrough. However, monkey embryos are much more similar to human embryos than mouse embryos. “This could have been the authors’ motivation to create artificial monkey embryos,” says Malte Spielmann, director of the Institute for Human Genetics at the University Medical Center Schleswig-Holstein.
‘However, it is not very surprising that it is significantly more complicated to produce artificial monkey embryos than synthetic mouse embryos.’ According to Spielmann, this so-called proof-of-concept study failed because the artificial monkey embryos were not viable and no pregnancy occurred. “In my view, the experiment does not provide any significant additional insights.” In his opinion, it would have been different if the synthetic embryos had gone through the entire organ development process. “This would open the door to making fully synthetic organs and studying them in the lab. Currently, all experiments fail before this critical window.”
After all, the experiments of the Chinese team confirm once again the previous work on mice and the astonishing ability of stem cells to self-organize into embryonic structures even in the laboratory. Like the group around Liu in the journal Cell Stem Cell reported, the monkey embryoids developed in the laboratory for up to eighteen days to the early stage of organ development; there were indications of the emergence of precursors to germ cells and hematopoietic tissue.
According to Liu and team, the embryoids created from embryonic stem cells are morphologically very similar to 8- to 9-day-stage embryos formed naturally through fertilization. Her animal model is therefore suitable for researching early stages of embryonic development without having to experiment with human embryos. Because such work is restricted worldwide.
So far, in most countries, you can only work with embryos that have grown in the laboratory for a maximum of 14 days. In Germany, the Embryo Protection Act has so far prohibited experiments on human embryos. It is still largely unclear how work with synthetic embryos, which are not created by fertilization of an egg cell but grown from stem cells, is to be assessed.
With material from the Science Media Center (SMC).