Researchers at the University of Cambridge and the California Institute of Technology reprogrammed stem cells to create synthetic human embryos in the laboratory, without sperm or an egg. Starting with a single embryonic stem cell, the embryos have no beating heart or brain but grew only to the start 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," reports The Guardian:
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[…]
There is also a significant unanswered question on whether these structures, in theory, have the potential to grow into a living creature. The synthetic embryos grown from mouse cells were reported to appear almost identical to natural embryos. But when they were implanted into the wombs of female mice, they did not develop into live animals.
"Our human model is the first three-lineage human embryo model that specifies amnion and germ cells, precursor cells of egg and sperm," lead researcher Magdalena Żernicka-Goetz said before presenting her research at the International Society for Stem Cell Research annual meeting. "It's beautiful and created entirely from embryonic stem cells."