“The embryo itself, in these very early post-implantation stages, is undergoing the critical cell-cell interactions that establish the body plan-and we do not have any easy way of studying those early stages”, Janet Rossant, senior scientist of developmental and stem cell biology at Toronto’s Hospital for Sick Children, told Motherboard”. And the technique could help to determine why some pregnancies fail.
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Professor Martin Pera, professor of stem cell science at the University of Melbourne, agreed the 14-day rule “needs to be revisited”, as this period of development is relevant to such conditions as early pregnancy loss and placental defects. Doing so would raise ethical, as well as technical, challenges.
However researchers at Cambridge University have now grown embryos for 13 days – a process they only stopped to avoid breaking the current legal limit of about 14 days. What could scientists in other nations do with this discovery, where ethical guidelines are more relaxed?
The 14-day rule prevents researchers from exploring the unique features of human embryos any later in development. “This is a bit hard to explain to my students”.
“Longer cultures could provide absolutely critical information for basic human biology”, she said. “It’s incredible to look at”, Zernicka-Goetz says.
But extending the time frame for such research likely would generate stringent opposition from those who believe human life begins at fertilization, and accordingly are against this type of medical experimentation.
Zernicka-Goetz’s group and a separate team at Rockefeller University in NY chose to try. “Rather, it is a public policy tool created to carve out a space for scientific inquiry and simultaneously show respect for the diverse views on human embryo research”. This new investigation reveals this process is not needed for the developing body of cells.
The scientists don’t yet know the function of the cell cluster, which, at its peak, forms 5-10% of the embryo. “Congress ought to have a full and open debate on the issue of human embryo research before the research community moves further without oversight”. “This is like discovering a new organ in your body”, Brivanlou says.
“Without this cavity, it would be impossible for the embryo to develop further as it is the basis for its future development”.
He said: “Knowledge of these processes could help improve the chances of success of IVF, of which only around one in four attempts are successful”.
The fertility industry could also benefit from new in vitro technology.
Human embryos normally implant into the wall of the uterus seven days after fertilisation.
“Since we are not providing any maternal factors, we can study just the effects at the level of the embryo”.
For the first time, scientists were able to observe the process of embryo implantation.
The ethics have not crystallized as neatly as the ability to grow human embryos, apparently.
“I do not see a politically, or, for most people, morally acceptable line after 14 days”, he said.
While extending the limit could allow scientists to answer key questions about how the embryo develops into different tissue types, and how sperm and eggs form within them, Zernicka-Goetz said she was not calling for a change in the law. It is also around the latest point at which an embryo can split into identical twins.
Researchers have broken the record for growing human embryos in the lab, keeping them alive and active beyond the stage when they would naturally implant in a mother’s womb. The authors note that the timeline was picked to be sensitive to the different views on when “a human embryo obtains sufficient moral status that research on it should be prohibited”.
“If you haven’t read Brave New World in a while, it’s time to refresh the memory”, said Dr. David Prentice, a professor of molecular genetics and an Advisory Board Member for the Midwest Stem Cell Therapy Center. He says that it is somewhat arbitrary. That, in the eyes of some religious bioethicists, marks the threshold at which an embryo is a distinct human. In 1984, the UK’s Warnock report reinforced the idea of a 14-day limit by pointing to the appearance of an alignment of cells around that time known as the primitive streak. “It’s an interesting ethical discussion we’ve got ahead of us here”, says Pera.
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“It’s really embarrassing at the beginning of the twenty-first century that we know more about fish and mice and frogs than we know about ourselves”, Ali Brivanlou, a developmental biologist at the Rockefeller University in New York City, said. But it’s a black box that’s very hard to study, as it’s too early to see much on an ultrasound, for example.
