Scientists grow primate embryos for 20 days

Xavier Symons
November 3, 2019
Reproduced with Permission

Two separate research teams in China have grown primate embryos in vitro for 20 days, in a development that has reignited debate over the 14-day limit on human embryo experimentation.

The new studies were published this week in Science, and experts in the field are excited about the results.

Both research groups grew monkey embryos on a gel matrix that supplied higher levels of oxygen than do cells in the womb. This culture technique was developed by researchers from California Institute of Technology in the United States, who in 2016 succeeded in growing human embryos for 13 days.

One of the research teams, led by biologist Ji Weizhi of the Yunnan Key Laboratory of Primate Biomedical Research in Kunming, China, reported that 46 of 200 monkey embryos in their study survived to 20 days. The other research team, led by Li Lei, a developmental biologist at the Chinese Academy of Sciences in Beijing, say they grew three embryos that long.

Both groups report that embryos in a dish develop in the same way as those in the womb. "It's OK to assume that the observations made are a representation of what happens in vivo," said Juan Carlos Izpisua Belmonte, a developmental biologist at the Salk Institute for Biological Studies and co-author of one of the studies.

Ji Weizhi said that he now wants to grow embryos to the point when the primitive nervous system starts to form, around day 20.

Scientists have used the new studies as an opportunity to restart debate about the 14-day limit on human embryo experimentation. Importantly, the developmental processes of monkey embryos are not identical to that of human embryos.

"In vitro cultured human embryos remain the irreplaceable system for us to study and understand human development," Fu Jianping, a bioengineer at the University of Michigan in Ann Arbor, told Nature News.