Thinkstock: In Greek Mythology, Chimeras are fire-breathing beasts.
How Chimeras Make Human-Pig Hybrids Possible
Stem cell technologies have enabled scientists to produce human cells and human tissues in pig and cattle embryos. This research was published in the journal Cell, but it should be noted that Dr. Jun Wu, staff scientist at the Salk Institute and head author, advised that generating human organs is beyond present capabilities: “Species evolve independently, and many factors dictating the developmental programs might have diverged, which makes it difficult to blend cells from one species to a developing embryo from another. The larger the evolutionary distance, the more difficult for them to mix.”
The experiment was ended after 28 days, but it is a firm step toward growing human organs in animals. Associate professor of bioethics and philosophy at Case Western Reserve University, Insoo Hyun, explains that, “They just wanted to see if the cells would survive during gestation, and they did, and they kind of migrated here and there to various sites, except the brain, which is interesting. . . . The next step would be then to see if they can get better at localizing where the human cells develop and, ideally, getting to organ genesis.”
Hyun is not unaware of the ethical questions and issues at hand: “If you up the biological contribution of the human stem cells, are you also somehow turning them morally into a human-like thing with human rights? It’s so difficult to know how you would actually address that. I would argue, as long as you are avoiding the brain, or there’s not a significant change to the brain, of structure and possible functioning, then I don’t think you even need to go down that philosophical path. . . . The emphasis should still remain on animal welfare.”
Even if many people are against the idea of the rich and the famous growing organs ad hoc and trying to live for hundreds of years, there are plenty of cases in which organs are needed just to give someone a chance at living to the age of retirement. If the methods outlined can be enhanced and advanced, growing functional human organs within pig embryos is theoretically possible. Again, using them for emergency transplants would save many innocent lives across the globe, but much still needs to be learned about how cells could be compelled to grow into the precise organs, tissues, and unique shapes which are required.
In the experiment discussed, human cells were successfully grown, but they almost certainly would have been rejected if they were transplanted into a human body. There was still too much pig tissue in the tissue that was produced, which should indicate just how much more work needs to be done before countless lives can be saved worldwide.
According to Prof Juan Carlos Izpisua Belmonte from the Salk Institute, “Humans and pigs are separated by a long time in evolution. . . . It is like a freeway with one car going much faster than another—you’re more likely to have an accident.” Until these methods are perfected, there is still hope that they could be utilized to screen for drugs, provide info on human diseases, and shed insight regarding early human embryo development.