Synthetic human embryos obtained from stem cells? Artificial monkey embryo research leads the way

IIn January 2017, I met Jiankui He, the now-infamous Chinese scientist who would go on to create the world’s first genome-edited babies. This occurred during a meeting in Berkeley, California hosted by Jennifer Doudna who, along with Emmanuelle Charpentier, was awarded the 2020 Nobel Prize in Chemistry for her work on CRISPR genome-editing technology.

In this meeting, geneticist George Church, known for his work reviving the woolly mammoth, described research into synthetic human embryos derived from stem cells. Church dubbed these embryo-like structures synthetic human entities with embryo-like characteristics.

At the time, the Church called for a careful and sustained dialogue on the moral merits of the 14-day limit on human embryo research.

Future, Man, Nature: Reading, Writing, Revolution An Evening with Dr. George Church of the Innovative Genomics Institute on Vimeo.

Structures similar to monkey embryos

This month, a team of Chinese scientists created synthetic monkey embryos or, more precisely, structures similar to synthetic monkey embryos from stem cells and used them for reproduction.

The reported research involved ain vitrostudy which means it was conducted in a laboratory as well as alivestudy, conducted in the body.

THEin vitroThe study involved ongoing culture of the monkey embryo-like structures in the lab to see how they might develop after the time when implantation typically occurs.

Under the microscope, these embryo-like structures initially looked like natural early-stage embryos created using eggs, sperm, and fertilization. They became disorganized over time, however, and only five of the 484 synthetic early-stage embryos survived to day 17.

THElivestudy involved transferring seven-day-old monkey embryo-like structures to eight female monkeys in hopes of becoming pregnant. Implantation occurred in three of the monkeys, but the pregnancies were short-lived. The synthetic monkey embryos stopped developing within 20 days after transfer and no fetuses were formed.

Beginning of pregnancy

The creation of non-human embryo-like structures is not new. In 2022, two research groups, one in Israel and another in the UK, reported the creation of mouse embryo-like structures from mouse stem cells.

Attempting to initiate pregnancy in female monkeys using monkey embryo-like structures is new, however, and suggests that it may one day be possible to attempt the same in humans. Presumably the goal would be to allow scientists to study early human development, including neurodevelopment, and to study pregnancy loss.

This most recent research raises a critical ethical question: Are human-like synthetic embryonic structures sufficiently different from human embryos created by fertilization to be exempt from current limits on human embryo research?

The question is timely since researchers have already used human stem cells to create a model of a human blastocyst.

Some researchers might argue that synthetic and natural human embryos are not the same thing and that synthetic human embryos should not be subject to the rules governing natural human embryos. Others will disagree.

Presumably the truth will depend on whether synthetic embryos can produce a live baby, but the only way to know is to do the experiment.

Research guidelines

Clearly this research, and previous studies, challenge the current international consensus on the 14-day rule which dictates that human embryos cannot be kept in the laboratory beyond 14 days after fertilization. The 14-day rule is to create a human blastocyst model and is a widely accepted research guideline in many countries around the world. It prohibits the development of human embryos outside the human body beyond 14 days.

This limit was introduced in the early 1980s. Up to 14 days, it was possible for a human embryo to divide and become a twin or for two human embryos to recombine and become a single individual.

Based on these biological facts, some have argued that before 14 days human embryos were not distinct individuals and therefore were not protectable human lives. They could be used for research in a laboratory and then discarded.

Others who have also argued for a 14-day cutoff for human embryo research have focused on a different developmental milestone, the primitive streak, which usually appears on day 15 and signals the development of the nervous system and brain.

Before 14 days, the human embryo could not feel pain and lacked the human reasoning ability. On this basis, a similar conclusion was reached: human embryos could be a legitimate object of research for up to 14 days.

Researchers have produced the first monkey blastoids, which could serve as good models of early human development. https://t.co/oGiCHuJACo

— News from Science (@NewsfromScience) April 11, 2023

Arbitrary limit?

Scientists have long argued that the 14-day limit is arbitrary and should be changed. Now that it is possible to keep natural embryos in culture beyond 14 days, and it may be possible to do so for synthetic embryos as well, some members of the scientific community are insisting that the 14-day limit should be reviewed or eliminated.

This notion took root in the 2021 research guidelines of the International Society for Stem Cell Research. The 2016 research guidelines banned research on human embryos beyond 14 days; however, the updated guidelines lifted this ban and did not propose an alternative, something colleagues and I have been critical of.

All of which makes me wonder if in the not-too-distant future I (and others) will be commenting on the ethics of the world’s first babies with stem cells. If so, will the comment be similar to the response to the first genome-edited babies, which was uniformly critical? Or, by then, will some celebrate it as a creative way to create designer babies?

Franoise Baylis is Distinguished Research Professor Emerita at Dalhousie University. Find Françoise on Twitter @FrancoiseBaylis

A version of this article was originally published at the Conversation and has been republished here with permission. Any repost should credit both the GLP and the original article. The conversation can be found on Twitter @ConversationUS