For example, the trophoblast, a precursor of the placenta, was present but not properly organised. Nevertheless, the scientists used a pregnancy test to assess how well the model embryos were growing when fluid from the dish was put on a test strip, it returned a positive result.ĭr Peter Rugg-Gunn, who studies embryonic development at the Babraham Institute near Cambridge, said the work was “impressive” and “significant”, but noted that not all the features of early human embryos were perfectly replicated. “This cannot be used for pregnancy,” he said. Because of their age at creation, Hanna said it was “biologically impossible” for them to implant into a womb. The freshly made model embryos are equivalent to week-old human embryos and are cultured in the lab for a further week. These went on to develop a placenta, a yolk sac, an outer membrane called the chorionic sac and other features expected in human embryos of the same age. They mixed together “naive” human stem cells, which are capable of turning into different cell types, and found that about 1% arranged themselves into “complete” embryo-like structures. Writing in Nature, the scientists describe how they built on procedures from last year to create model mouse embryos. Since pregnant women are often excluded from clinical trials, doctors are in the dark about the side-effects of even some of the most common treatments on pregnant women and babies. Before growing a model embryo for donor tissue, scientists would tweak its genetics to ensure it did not develop a brain or nervous system, he added.Īnother application scientists have in mind is using model embryos to assess the probable impact of medicines on real human embryos.
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“Do they have the right to give their own skin cells to make an embryo model and make cells that will save their lives or solve their medical need? That is the scenario that should be considered,” Hanna told the Guardian.
Grow the model embryos for a month or so and they will start to develop organs that can be used as a source of cells to transplant into the patients, he says. Another scenario Hanna envisages is the creation of model embryos from the skin cells of ill patients. Understanding embryo development – particularly from two weeks in the womb – is only one area where scientists see model embryos having an impact. While the minuscule structures are not identical to human embryos, researchers hope they will soon be good enough to help shed light on the mysteries of the earliest stages of human development and so far unknown causes of miscarriage.
The field has produced a flurry of papers in recent months from scientists who have combined stem cells to create human embryo-like structures without the need for eggs or sperm. At two weeks, the balls of cells were about half a millimetre wide.
“This is the first embryo model that has structural compartment organisation and morphological similarity to a human embryo at day 14,” said Prof Jacob Hanna, who led the research at the Weizmann Institute in Israel.
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