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Scientists create human-ape embryos

Human / animal chimeras could also help fill gaps in our understanding of early human development after conception, and improve the study of how viruses, bacteria, drugs and devices work in humans, said Farahany and Greely.

“The kind of animal models we have right now are not enough to model most of the diseases that humans suffer from – especially brain diseases that humans suffer from, but actually any disease,” Farahany said. “This means that when you’re trying to test a drug or trying to figure out how a disease occurs or develops, we don’t have very good models for doing it right now.”

For example, such a human / animal chimera could help us better understand why the Zika virus causes birth defects in the children of infected pregnant women, Farahany said.

In 2017, members of this research team reported incorporating human cells into early stage porcine tissues, but the contribution of human cells was quite small.

So the researchers set out to create a chimera in a species closer to humans – the macaque monkey species.

Six days after 132 monkey embryos were created in the lab, each was injected with 25 human stem cells.

After 10 days, 103 of the chimeric embryos were still developing. Survival quickly began to decline, and by day 19, only three chimeras were still alive.

Importantly, the percentage of human cells in embryos remained high throughout their growth, the researchers said – meaning the human cells integrated into the host monkey species.

“Human cells have survived, proliferated and generated several… cell lines” inside monkey embryos, said lead researcher Juan Carlos Izpisua Belmonte, professor at the gene expression laboratory at the Salk Institute for Biological Studies in La Jolla , in California.

The creation of such human / ape chimeras “will allow us to better understand whether there are barriers imposed by evolution to the generation of chimeras and whether there are ways in which we can overcome them,” said Izpisua Belmonte in A press release.

According to Greely, “the hope was that human cells would work better in monkey embryos, and they could understand why they work better in monkey embryos and use that knowledge to make them work better in pig embryos.”