Interestingly, the review paper suggests that perhaps the creation of human-animal chimeras might help people realize that humans don’t necessarily have any higher moral status than any other creature. There are also animal welfare concerns – would these chimeras be healthy enough to live relatively normal lives, or might they be prone to suffer from lifelong health problems? Would they need to be isolated from other animals, a cruelty in itself? What rights would these chimeras have? Does it depend on the degree of “humanity” in them? Can chimeras be owned by people? More profound ethical questions may arise around the blurring of the line between humans and animals, as raised by a 2019 review paper in the Journal of Law and the Biosciences. The announcement of the new chimeras will no doubt be labelled “unnatural” or “playing God” by some people – but the same could be said about many scientific breakthroughs. These are noble causes, but are they worth the ethical minefield? And because they could be grown on demand from a patient’s own cells, the risk of rejection is removed, as is the need for immunosuppressant drugs.Ĭhimeric monkeys could be a similar vector for transplantable tissues, but they might also be more useful as “humanized” test subjects for new drugs or medical treatments, or to study diseases in a manner where the results would be closer to what we can expect in humans. However all of this begs a few very important questions – why? And should we be doing this at all? In the case of chimeric pigs, the ultimate goal is to grow human organs for transplant, to reduce the need for long waiting lists. "Generation of a chimera between human and non-human primate, a species more closely related to humans along the evolutionary timeline than all previously used species, will allow us to gain better insight into whether there are evolutionarily imposed barriers to chimera generation and if there are any means by which we can overcome them.” "Historically, the generation of human-animal chimeras has suffered from low efficiency and integration of human cells into the host species," says Izpisua Belmonte. Using monkeys, to whom we’re much more closely related, improves the chances of successful chimeras. The problem is that humans and pigs are, obviously, quite different species separated by tens of millions of years of evolution. That said, only tiny amounts of human cells were detected, far too few to be practical. This was the first time human cells had been shown to be able to grow inside the blastocyst of another animal. In 2017, some of the same scientists created human-pig chimeras, by introducing human stem cells into pig embryos and incubated them in surrogates for four weeks. This isn’t the first human-animal chimera to be created. Weizhi Ji, Kunming University of Science and Technology ![]() "An important goal of experimental biology is the development of model systems that allow for the study of human diseases under in vivo conditions." "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," says Juan Carlos Izpisua Belmonte, senior author of the study. The goal, the team says, is to make better models for studying biological development, evolution, disease progression and treatments. This successful experiment showed that human cells can survive and proliferate in monkey embryos, in relatively high numbers. After that, the embryos were terminated before they developed any further. After 10 days, there were 103 of these chimeric embryos remaining, but by day 19 only three still survived. Six days after fertilization they were injected with 25 human extended pluripotent stem (hEPS) cells, which contribute to the tissue as the embryo develops.Īnd sure enough, when the researchers examined the batch of embryos 24 hours later, they detected human cells in 132 of them. In lab tests in culture, the team started with monkey blastocysts. And in the new study, researchers from the Salk Institute and Kunming University of Science and Technology successfully created chimeras of humans and monkeys. ![]() Scientists have been experimenting with interspecies chimeras for decades, merging similar animals like mice and rats, and sheep and goats. It can occur naturally during development, such as when non-identical twins merge early on, or it can be an artificial process – technically, organ transplants create chimeras.īut it doesn’t necessarily need to be cells from the same species. But of course they also raise some complicated ethical concerns.Ī chimera is, put simply, an organism that contains cells from more than one individual. These chimeras pave the way for more accurate models of human biology and disease, which could open up a range of new medical benefits. In a breakthrough new study, scientists have created human-monkey chimera embryos for the first time.
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