Ethicists urge caution after creation of monkey embryos containing human cells

A human-monkey chimeric blastocyst. Credit: Weizhi Ji/Kunming University of Science and Technology. A human-monkey chimeric blastocyst. Credit: Weizhi Ji/Kunming University of Science and Technology.

Catholic scientists and ethicists have warned of the potential for a slippery slope in response to reports that scientists had successfully created a “chimeric embryo” that was part macaque monkey and part human. 


An article published April 15 in the journal “Cell” described how scientists took a blastocyst from a macaque and added human cells. The blastocyst then developed into a chimeric embryo, meaning it has parts of two species. It is the goal that these beings could be used to grow human organs, which would then be used in transplantation. 


Similar experiments have occurred using other animals; this was the first time a monkey-human chimera had been created. 


“When it comes to the ethics of mixing cellular materials between humans and animals to produce ‘chimeric animals,’ the details of what researchers are doing will be of the essence,” Fr. Tad Pacholczyk, the director of education at the National Catholic Bioethics Center, told CNA.


An ethical example of this research, he said, would be to “implant human stem cells into embryonic monkeys in order to grow human hearts, kidneys, and other organs inside the monkey animal, primarily to alleviate serious donor shortages for organ transplants.” 


This would be ethical “as long as certain limits and boundaries are respected.” 


The reverse, however--adding monkey stem cells to a human--would “raise grave ethical objections,” he said. 


Fr. Pacholczyk told CNA that among the boundaries needed for ethical experimentation of this type were a “goal to induce one species, the monkey, to grow an organ or tissue of the other,” instead of a goal of a creation of a “new” species.


“The procedures must not involve the replication of major pillars of human identity or human cognition in the monkey, such as through the human brain system,” he said, adding that the monkey should not be able to produce human gametes either.

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Additionally, said Fr. Pacholczyk, “The procedures must not involve the creation, destruction or exploitation of human embryos,” and “The stem cells used for creating chimeric animals must be ethically-sourced.” 


“In general, we make use of animals for a wide range of purposes — we eat them, we use them to make clothing, we use them for basic scientific research — so if we can use them to generate needed organs to save people’s lives without crossing fundamental ethical lines, this approach should be helpful,” he said. 


Fr. Nicanor Austriaco, O.P., a professor of biology at Providence College, had a more sceptical view on the ethical nature of human-animal chimeras. Fr. Austriaco told CNA that the creation of animal-animal chimeras “could be justified if there were a pressing research question that would benefit human health.” 


“However, it is problematic to attempt to make human-animal chimeras with primate embryos because of the danger that we could make a disabled human,” he said. “There are other animals like pigs that could be used to grow transplantable organs.”

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Fr. Austriaco told CNA that he is “troubled” by this type of experimentation. 


“I do not believe that our post-Christian and utilitarian society has the moral resources to draw the boundaries that should limit research with embryonic humans,” he said. “Experiments are thought to be justifiable if they can help some ease their suffering and pain.” 


While similar experiments with pigs have been less successful, Fr. Austriaco called these experiments “an alternative that is not ethically fraught with danger in the same way.”  


“I think that there is a genuine desire to advance human health and well-being,” he said. “However, in a post-Christian society that legalizes abortion, there is often little concern with creating and using human embryos as long as the science ‘helps’ people.”

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