The future of organ transplants may lie in the animal kingdom for cross-species organ donation—a process known as xenotransplantation.
Human organs would be grown inside a pig’s body. Scientists are experimenting with planting human stem cells into pig embryos in the hopes of growing hearts, livers and other body parts that could be used for transplants.
According to MIT Technology Review, researchers in the US brought about an estimated 20 pregnancies of pig-human and sheep-human chimeras in 2015, although none of the chimeras were brought to term.
Scientists have already successfully managed to genetically modify pig embryos so that the fetal pig lacks a heart or other organs or tissues. Their hope is that, by injecting human stem cells into the embryos, they can prompt human cells to create the missing organ. Cardiologist Daniel Garry tells the MIT Technology Review that he has successfully experimented with this approach by injecting the stem cells of another pig into the genetically modified embryo. The US Army recently awarded Garry a $1.4 million grant to continue his research on growing human hearts in swine.
These chimeras are not without controversy. Pope Francis reportedly approved their creation, but the National Institutes of Health announced in 2015 that it would not fund research involving human-animal chimeras until they have reviewed it further. The concern is that these experiments might blur the lines between human and animal—particularly if the animals grow human brain cells. As NIH ethicist David Resnik told MIT, “The specter of an intelligent mouse stuck in a laboratory somewhere screaming ‘I want to get out’ would be very troubling to people.” How many human organs does a pig need to have before it is considered more human than not?