Earlier today, reports emerged that researchers at the Salk Institute had, for the first time, successfully created human/pig chimera embryos. Juan Carlos Izpisúa Belmonte, the scientist leading the effort, wrote an article for the November 2016 issue of Scientific American describing his dream of using chimeric animals to grow human organs for patients needing transplants.
While the idea of a human/pig chimera may conjure ghastly images of freakish-looking hog-people, the reality is much less disturbing. In fact, one of the most notable successes of the experiment, according to Belmonte, was that the contribution of the human cells to the developing pig embryo was very small. The fear, from an ethical standpoint, had been that the human cells would over-contribute, straying from the target site to the developing brain, for example. This did not happen, and the human cells survived the full four months during which the embryos were allowed to develop.
The researchers encountered many challenges throughout the study, making clear that despite the relative success of this experiment, creating a whole, mature human organ in an animal remains a distant prospect. Nonetheless, the work continues. The graphic below breaks down how researchers hope the process will one day work.