Scientists report they have grown the early stages of a human embryo-like entity without using sperm, an egg or a womb.
The ’embryo model’ even releases hormones that triggered a positive pregnancy test.
However, the purpose of the embryo is to provide an ethical way of monitoring early human development. Synthetic embryos would not be allowed to progress beyond a matter of weeks.
During the first 14 days after an egg is fertilised by a sperm, the nascent embryo undergoes dramatic changes. It is at this point that myriad developmental disorders and birth defects can arise, but the cause of these is poorly understood.
The first two weeks are also a major source of miscarriage.
Speaking to the BBC, co-author Professor Jacob Hanna, from the Weizmann Institute of Science, said: ‘It’s a black box and that’s not a cliche – our knowledge is very limited.’
Across the world teams are racing to develop better ways to understand this crucial time. Earlier this year a team from the University of Cambridge and California Institute of Technology created synthetic embryos using only stem cells. The latest breakthrough, published in the journal Nature, also used stem cells – and the team describes their results as the first ‘complete’ embryo model, one that mimics key cells and structures throughout the first two weeks of development.
‘This is really a textbook image of a human day-14 embryo, [which] hasn’t been done before,’ said Professor Hanna.
The team used a cocktail of chemicals to ‘coax’ the stem cells into transforming into four key embryonic cells – epiblasts, trophoblasts, hypoblasts and extraembryonic mesoderm cells.
‘I give great credit to the cells – you have to bring the right mix and have the right environment and it just takes off,’ said Professor Hanna. ‘That’s an amazing phenomenon.’
The team allowed the embryos to develop to the 14-day mark, the widely-accepted legal cut-off for embryo research in any form.
However, the use of synthetic embryos may prompt reconsideration of this rule, enabling scientists to further understand early human development.
Under UK law, embryo models are distinct from human embryos.
Scientists working on synthetic embryos hope developing an artificial duplicate of human cells will further understanding of inherited diseases, and show how organs develop.