This does potentially hold a great deal of promise to solve the shortage of available organs for transplant.
However, one concern is the issue of disease. It has always been somewht difficult for diseases to cross species barriers, this may open an easy route for Swine diseases to mutate/adapt themselves to Humans. And those diseases can be deadly.
---------------------- Human-pig ‘chimera’: Ethics and medical promise of growing human organs in animals
Pig embryos that had been injected with human stem cells when they were only a few days old began to grow organs containing human cells, an advance that promises — or threatens — to bring closer the routine production of creatures that are part human and part something else.
These human-pig “chimeras” were not allowed to develop past the fetal stage, but the experiment suggests such creations could eventually be used to grow fully human organs for transplant, easing the fatal shortage of organs: 120,000 people in the United States are waiting for lifesaving transplants, but every day two dozen die before they get them.
The creation of “intermediate forms” of life is thought by some critics to “denigrate human dignity and blur the line between what is human and what is not, especially if you believe that we were created in the image of God,” said bioethicist and legal scholar Hank Greely of Stanford.
If the marriage of stem cells and CRISPR follows a path [similar to Dolly the sheep], it might not be long before pigs have enough Homo sapiens in them not only to grow human hearts, lungs, livers, and kidneys for transplant but also to model human diseases more closely than current lab animals do and to test experimental drugs.