Scientists at the Weizmann Institute in Rehovot, Israel, were able to make stem cells taken from mice form early embryo-like structures, including a gastrointestinal tract, a beating heart, and the early stages of a brain. The embryos are considered “synthetic” because they were not derived from a fertilized egg — but preliminary results suggest that “synthetic embryos” are fairly similar to natural embryos.
“Remarkably, we show that embryonic stem cells generate whole synthetic embryos, meaning this includes the placenta and yolk sac surrounding the embryo,” said Dr. Jacob Hanna, who headed the study. “We are truly excited about this work and its implications.”
Researchers believe that this breakthrough could offer alternatives to animal experimentation and pave the way for new stem cell growth for human transplants. Skin cells could be potentially transformed into bone marrow stem cells, for example, to help treat patients suffering from leukemia. The demand for donated organs often outstrips the supply, and the immune system naturally attacks foreign cells, requiring already weakened patients to take immunosuppressant drugs after a transplant. Being able to grow tissues from a patient’s DNA could bypass many of the compatibility issues current transplants face and greatly increase the availability of the treatment.
The synthetic embryos are not thought to have the potential to develop into fully-formed animals, and only 0.5% of the observed stem cells combined to grow distinctive tissue, although those tissues seemed fully functional and “95%” similar to natural tissues in basic structure.
Synthetic embryos failed to develop further when they were implanted into female mice. Human experimentation is purely hypothetical at this stage, although Hanna is optimistic about prospects for future research.
“In Israel and many other countries, such as the US and the UK, it is legal and we have ethical approval to do this with human-induced pluripotent stem cells. This is providing an ethical and technical alternative to the use of embryos,” Hanna said.
Other researchers are more uncertain about the practical and ethical prospects of future experimentation.
“Synthetic human embryos are not an immediate prospect. We know less about human embryos than mouse embryos and the inefficiency of the mouse synthetic embryos suggests that translating the findings to human requires further development,” Dr. James Briscoe, a researcher at London’s Francis Crick Institute, said to The Guardian. “Now is a good time to consider the best legal and ethical framework to regulate research and use of human synthetic embryos and to update the current regulations.”
Hanna’s team has made many breakthroughs researching mouse embryos. Last year, they created an artificial womb that enabled natural mouse embryos to grow for several days, and more recently, they used the same device to sustain synthetic embryos for more than a week, nearly half the gestational period for a mouse.