In August 2022, the journals Cell and Nature reported a pioneering achievement in the field of life sciences: synthetic mouse embryos created with stem cells, aspermiac, egg participation, complete stem cell assembly, implanted in the uterus and successfully developed organs. (For details, see Cell first, then Nature, artificial embryos that do not require fertilized eggs have developed brains...) ）
At the time, the research team expressed the idea that the results could provide more new insights into embryonic development, answer the question of why early embryonic development often fails, and perhaps even advance efforts in laboratory culturing organs to lead to fully functional artificial organs.
Time is like an arrow, technology is galloping. The scholars who imagined the future 10 months ago presented their new result 10 months later at the International Society for Stem Cell Research Annual Meeting: human embryos created directly from stem cells.
Team leader and developmental biologist Magdalena Zernicka-Goetz said: "We can create models that approximate human embryos by reprogramming embryonic stem cells. "These model embryos provide a critical window into our understanding of the impact of genetic disease and also help shed light on the biological causes of recurrent miscarriage."
Of course, the work of Gertz and others has also caused great ethical and legal controversy.
Synthetic human embryos do not have the origin of organs such as the heart and brain, but contain cells that continue to form the placenta, yolk sac, and the embryo itself.
From the perspective of clinical application, the prospect of synthetic embryos in the near future is not optimistic; From a legal point of view, implanting them in the human uterus is undoubtedly illegal. At present, it is not clear whether it is possible for these structures to continue to mature beyond the initial stages of development.
An important purpose of the work on artificial embryos is to give scientists an understanding of the so-called "black box" period of human development.
Currently, scientists are only allowed to grow embryos in the laboratory for up to 14 days (legal period); After 14 days, they can only learn more about the development process by looking at pregnancy scans and embryos donated for scientific research.
According to Gertz at the annual stem cell meeting, they cultured artificial embryos to a stage just beyond 14 days of natural embryonic development, the stage where gastrulation begins to form. (Between days 14 and 22 of development, the embryo undergoes a gastrulation stage.) Of course, the full details of their latest work have not yet been published in the journal.
When the gastrulation stage begins, the embryo transitions from a continuous cell layer to forming different cell lines and establishing the basic axes of the body (embryo); At this stage, the embryo does not yet have a heart, intestine, or brain, but the model embryo tells us that the original cell, the precursor cells of the egg and sperm, is already present.
Synthetic mouse embryos after 8 days of development
Gertz said: "Our model is the first 'trilineage human embryo' model, which specifies the amniotic membrane and germ cells, the precursor cells of the egg and sperm, and it is beautiful, created entirely from embryonic stem cells. ”
There is no doubt that artificial embryo technology is advancing far faster than the law is perfecting, and many scientists around the world have begun to develop voluntary guidelines to govern synthetic embryos. Robin Lovell-Badge, a stem cell biologist at the Francis Crick Institute in the UK, notes:
"If our big goal is to make these models highly similar to natural embryos, then in a sense, we should treat artificial embryos like natural embryos." However, this is not currently required by law. There are concerns about this. ”
In addition, there is a very critical question: is it possible for synthetic embryos to develop into organisms?
In previous work, synthetic embryos grown from mouse stem cells were almost identical to natural embryos; But when they were implanted in the uterus of female mice, they only developed organs and eventually did not become live animals.
In April 2023, a team from the Chinese Academy of Sciences created synthetic embryos from monkey cells and implanted them in the uterus of adult mothers, some of which showed the first signs of pregnancy, but none of them continued to develop for more than a few days.
Scientists say it's unclear whether the barriers to further development are technical or have more fundamental biological causes. This unknown potential makes the need for better legislation all the more urgent.
Source:
Synthetic human embryos created in groundbreaking advance
Advances in synthetic embryos leave legislators needing to catch up
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