Scientists have developed embryos that are part human and part monkey.
As described in the scientific journal Cell, the scientists created the embryos to find new methods to produce organs for people who need transplants. However, the research raises numerous concerns.
“My first question is: Why?” asked Kirstin Matthews, a fellow for science and technology at Rice University’s Baker Institute. “I think the public is going to be concerned, and I am as well, that we’re just kind of pushing forward with science without having a proper conversation about what we should or should not do.”
The team of international scientists, however, defends their experiment.
“This is one of the major problems in medicine — organ transplantation,” says Juan Carlos Izpisua Belmonte, a professor in the Gene Expression Laboratory of the Salk Institute for Biological Sciences in La Jolla, California and co-author of the Cell study. “The demand for that is much higher than the supply.”
“I don’t see this type of research being ethically problematic,” Insoo Hyun, a bioethicist at Case Western Reserve University and Harvard University said. “It’s aimed at lofty humanitarian goals.”
Hyun also noted that thousands of people die every year in the United States while waiting for an organ transplant. Researchers in the U.S. and around the world have been injecting human stem cells into sheep and pig embryos to see if they are capable of growing human organs in animals.
So far, however, that method has not been successful. So Belmonte teamed up with scientists in China and other countries to take a different approach. The team of researchers injected 25 cells from humans, commonly called iPS cells, into embryos from macaque monkeys. This type of monkey is much more closely genetically related to humans than sheep or pigs.
After just one day, the scientists said they were able to detect human cells growing in 132 of the embryos.
“This knowledge will allow us to go back now and try to re-engineer these pathways that are successful for allowing appropriate development of human cells in these other animals,” Belmonte said. “We are very, very excited.”
Mixed-species embryos are referred to as “chimeras,” named after the fire-breathing part-lion, part-goat, part-snake creature from Greek mythology.
“Our goal is not to generate any new organism, any monster,” Belmonte said. “And we are not doing anything like that. We are trying to understand how cells from different organisms communicate with one another.”
The team also hopes that this research could lead to new developments in aging and underlying causes of cancer and other diseases.
Other scientists agree the research could be very useful.
“This work is an important step that provides very compelling evidence that someday when we understand fully what the process is we could make them develop into a heart or a kidney or lungs,” says Dr. Jeffrey Platt, a professor of microbiology and immunology at the University of Michigan.
The biggest concern with this type of research, however, is ethics. The team says that someone could potentially try to make a baby out of an embryo this way. Human cells could become part of the developing brain of this type of embryo — and of the brain of the resulting animal.
“Should it be regulated as human because it has a significant proportion of human cells in it? Or should it be regulated just as an animal? Or something else?” says Matthews. “At what point are you taking something and using it for organs when it actually is starting to think, and have logic?”
Another concerning possibility is that using human cells this way could create animals that have human sperm or eggs.
“Nobody really wants monkeys walking around with human eggs and human sperm inside them,” says Hank Greely, a Stanford University bioethicist. “Because if a monkey with human sperm meets a monkey with human eggs, nobody wants a human embryo inside a monkey’s uterus.”
Greely also said that he hopes this study will spark a wider debate on how far scientists should be allowed to go with this type of research.
“I don’t think we’re on the edge of beyond the Planet of the Apes. I think rogue scientists are few and far between. But they’re not zero,” Greely said. “So I do think it’s an appropriate time for us to start thinking about, ‘Should we ever let these go beyond a petri dish?'”