Synthetic embryos sit at a unique juxtaposition: scientifically fascinating, ethically challenging and, for the most part, entirely unregulated by current legislation. The latest work by Prof Magdalena Żernicka-Goetz’s team brings these issues into stark relief and show that developments in this field are happening so quickly that the science is rapidly outpacing the law.
The motivation for creating embryo models in the lab is relatively uncontroversial. For the avoidance of doubt, there are no plans to create lab-grown babies. The aim is to obtain unprecedented insights into a window of human development that until now has largely remained a “black box” because it falls beyond the legal limit up to which scientists can cultivate embryos in the lab, and before a pregnancy’s progress can be detected on a scan.
Scientists including Żernicka-Goetz have worked for years to develop lab-based models that can lift the lid on this crucial period of development. Until recently, though, such models could only be coaxed along the very earliest stages of development before they stopped maturing, and were only a rough approximation of what occurs in nature.
In the past few years this picture has changed. Last year, in a groundbreaking advance, scientists succeeded in creating synthetic mouse embryos that bore a remarkable resemblance to the natural equivalents, including having a beating heart and primitive brain-like structure. In April, a Chinese team reported implanting synthetic embryos created from monkey cells to produce short-lived pregnancies.
The latest work shows that these sophisticated culture systems, designed to mimic the environment of the womb, can also be used to create human stem cell embryo models. According to the team behind the work, this allowed them to replicate important steps in development up to the equivalent of about 14 days in a natural embryo – and possibly just beyond this point.
So far, none of the animal model embryos has gone on to produce living animals, but some think that may eventually be possible. In her comments on Thursday, Żernicka-Goetz pointed out that her team was now able to cultivate the synthetic mouse embryos to the same stage as they could achieve with natural mouse embryos obtained through fertilising an egg with sperm.
As these models mirror the pathway of natural embryos ever more closely, their scientific value increases. But there is also a growing need for clear ethical and legal boundaries, which do not currently exist. It is crucial that scientists proceed cautiously and that legislators, including in the UK, take urgent steps to catch up.
