Pioneering experiment may help to understand genetic diseases and miscarriages, but raises ethical and legal debate. The model is not identical to a natural embryo, and survival in a real uterus is still uncertain. A team of researchers based in the United States and the United Kingdom claims to have created, for the first time in the history of science, synthetic versions of human embryos from stem cells, without the use of eggs or sperm.
Although they resemble real embryos at an early stage of development, these models do not have all the characteristics of a natural embryo: they do not have a functioning heart or brain structure, but they do have cells that, in human pregnancies, would later lead to the formation of the placenta , the yolk sac and the embryo itself.
However, it remains to be seen whether these structures would be able to continue to develop if implanted in a human uterus – moreover, such a procedure would be illegal.
The team behind the experiment, conducted in the US and UK, say they want to understand why pregnancies fail – a growing concern amid the popularization of assisted fertilization methods. There is also the expectation that it can contribute to the study of genetic diseases.
The study is led by Magdalena Żernicka-Goetz, from the University of Cambridge and the California Institute of Technology, and was presented this Wednesday (14/06) in Boston during a meeting of the International Society for Research in Stem Cells (ISSCR ).
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ethical and legal debate
Although, for the time being, there is no prediction of the clinical use of these embryos, the research raises ethical and legal debates.
While natural embryos fertilized in the laboratory from eggs and spermatozoa can only be legally cultivated for up to 14 days, the synthetic embryos in the study are not covered by specific legislation and would have been cultivated until reaching a stage beyond that mark: that of gastrulation, when the embryo ceases to be a cluster of identical cells and begins to form distinct units that, later, will form basic structures for the development of a fetus.
The same group of scientists involved in this experiment had already proved before that it was possible to create a mouse embryo from stem cells, equipped with an intestinal tract, the beginning of a brain and a beating heart.
The rodent experiment would have shown that the synthetic embryos would be almost identical to the natural ones, but they did not survive uterine implantation.
In April, Chinese scientists replicated the experiment in monkeys, but no embryos developed for more than a few days after uterine implantation.
Scientists say they do not know whether the barrier to development is merely technical or has a biological cause.
