Scientists in Israel reported Wednesday in the journal Nature that they have successfully grown apparently normal mouse embryos in an artificial uterus, marking the first time a mammal has been nurtured to half-term outside the womb. Dr. Jacob Hanna and his colleagues at the Weizmann Institute of Science described removing a fertilized egg at five days of gestation and watching it develop for another six days in glass vials inside a special rotating incubator Hanna spent seven years developing.
Hanna’s “artificial womb may allow researchers to learn more about why pregnancies end in miscarriages or why fertilized eggs fail to implant,” The New York Times reports. “It opens a new window onto how gene mutations or deletions affect fetal development. Researchers may be able to watch individual cells migrate to their ultimate destinations,” unlocking mysteries about how a single cell develops into the trillions of specific cell types that make up a living creature.
Hanna told the Times that since submitting the paper to Nature, he and his team have grown mouse embryos from right after fertilization to the 11-day mark, at which point the embryos need blood supply typically provided by the placenta to continue developing. Full gestation for a mouse embryos is about 20 days. When Hanna compared his 11-day-old embryos to those from a mouse uterus, they were identical.
Hanna is now working on ways to adapt his artificial womb so mice embryos can grow to term, possibly by adding an artificial blood supply or using an enriched nutrient solution, he told the Times. Other researchers have found ways to develop mouse embryos from fibroblasts, or connective tissue cells, getting rid of the need for a fertilized egg. Two other studies in Wednesday’s Nature described attempts to use the same technique to develop human embryos.
Putting all these developments together, “it is not unreasonable that we might have the capacity to develop a human embryo from fertilization to birth entirely outside the uterus,” Paul Tesar, a developmental biologist at Case Western Reserve University School of Medicine, told the Times. “Whether that is appropriate is a question for ethicists, regulators, and society.”