Interspecies embryos grown

A JOINT team of US and Chinese scientists have, in breakthrough research, grown human cells in monkey embryos in a laboratory for up to 20 days. The development, which has sparked ethical debates, has implications for developing new models of human biology and disease.

Interspecies chimeras in mammals have been made since the 1970s, when they were generated in rodents and used to study early developmental processes.

In the current study, detailed in the journal Cell, six days after the monkey embryos had been created, each one was injected with 25 human cells. The cells were from an induced pluripotent cell line known as extended pluripotent stem cells, which have the potential to contribute to both embryonic and extra-embryonic tissues.

After one day, human cells were detected in 132 embryos. After 10 days, 103 of the chimeric embryos were still developing.

Survival soon began declining, and by day 19, only three chimeras were still alive. Importantly, though, the percentage of human cells in the embryos remained high throughout the time they continued to grow.

“As we are unable to conduct certain types of experiments in humans, it is essential that we have better models to more accurately study and understand human biology and disease,” said Juan Carlos Izpisua Belmonte, professor at the Gene Expression Laboratory at the Salk Institute for Biological Sciences.