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, according to Farahany and Greely.
“The kind of animal models we have right now aren’t enough to model most of the diseases that humans suffer from – especially brain diseases that humans suffer from, but really every disease,” Farahany said. “That said, if you’re trying to test a drug or understand how a disease develops or develops, we don’t have very good models right now to do it.”
For example, such a human / animal chimera could help us better understand why the Zika virus causes birth defects in children of infected pregnant women, Farahany said.
In 2017, members of this research team reported that they incorporated human cells into pig tissue at an early stage, but the contribution of human cells was relatively small.
So the researchers set out to create a chimera in a species that is more closely related to humans – the ape macaque.
Six days after 132 monkey embryos were made in the laboratory, 25 human stem cells were injected into each.
After 10 days, 103 of the chimeric embryos developed. Survival soon began to decline and by the 19th day only three chimeras were alive.
Importantly, the percentage of human cells in the embryos remained high throughout their growth, the researchers said – meaning the human cells integrate with the host monkey species.
“The human cells survived, multiplied, and created multiple … cell lines” within the monkey embryos, said lead researcher Juan Carlos Izpisua Belmonte, a professor at the gene expression laboratory at the Salk Institute for Biological Studies in La Jolla, California.
The creation of such human and ape chimeras “will allow us to gain a better understanding of whether there are evolutionarily imposed barriers to the creation of chimeras and whether there are means by which we can overcome them,” Izpisua Belmonte said in one Press release in a magazine.
According to Greely, “the hope was that human cells would work better in monkey embryos, and they could figure out why they work better in monkey embryos and use that knowledge to make them work better in pig embryos.”
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