Synthetic Human Embryos Created In Groundbreaking Device

Scientists have created synthetic human embryos using stem cells, in a groundbreaking advance that sidesteps the need for eggs or sperm. Scientists say these model embryos, which resemble those in the earliest stages of human development, could provide a crucial window on the impact of genetic disorders and the biological causes of recurrent miscarriage. However, the work also raises serious ethical and legal issues as the lab-grown entities fall outside current legislation in the UK and most other countries. The structures do not have a beating heart or the beginnings of a brain, but include cells that would typically go on to form the placenta, yolk sac and the embryo itself.

There is no near-term prospect of the synthetic embryos being used clinically. It would be illegal to implant them into a patient’s womb, and it is not yet clear whether these structures have the potential to continue maturing beyond the earliest stages of development. The motivation for the work is for scientists to understand the “black box” period of development that is so called because scientists are only allowed to cultivate embryos in the lab up to a legal limit of 14 days. They then pick up the course of development much further along by looking at pregnancy scans and embryos donated for research. The full details of the latest work, from the Cambridge-Caltech lab, are yet to be published in a journal paper. But, speaking at the conference, Zernicka-Goetz described cultivating the embryos to a stage just beyond the equivalent of 14 days of development for a natural embryo.

The model structures, each grown from a single embryonic stem cell, reached the beginning of a developmental milestone known as gastrulation, when the embryo transforms from being a continuous sheet of cells to forming distinct cell lines and setting up the basic axes of the body. At this stage, the embryo does not yet have a beating heart, gut or beginnings of a brain, but the model showed the presence of primordial cells that are the precursor cells of egg and sperm. “Our human model is the first three-lineage human embryo model that specifies amnion and germ cells, precursor cells of egg and sperm,” Zernicka-Goetz told the Guardian before the talk. “It’s beautiful and created entirely from embryonic stem cells.”