Nearly 120,000 Americans are on the organ transplant waiting list. Wouldn't it be great to grow made-to-order human organs suitable for transplant in pigs? In today's Cell, researchers associated with the Salk Institute for Biological Studies report achieving the first step toward that goal. They created induced pluripotent human stem cells that the researchers injected into pig embryos which were then implanted into the uteruses of sows where the embryos were allowed to develop for four weeks. Testing the embryos, the researchers did detect that the human stem cells had begun to grow and differentiate into different kinds of precursor cells including those for heart, liver and neurons. The process was inefficient, possibly due to developmental differences that arose over the course of evolution between humans and pigs. Nevertheless, the researchers concluded, "Ultimately, these observations also raise the possibility of xeno-generating transplantable human tissues and organs towards addressing the worldwide shortage of organ donors."
The Washington Post notes that this success worries some folks who "think there's a symbolic or sacred line between human and animal genetic material that should not be crossed." In fact, back in 2009 some bioconservatives in Congress introduced legislation that would have outlawed some aspects of this type of research. One of the sponsors of the bill, then-Sen. Sam Brownback (R-Kan.) declared, "This legislation works to ensure that our society recognizes the dignity and sacredness of human life. Creating human-animal hybrids, which permanently alter the genetic makeup of an organism, will challenge the very definition of what it means to be human and is a violation of human dignity and a grave injustice." Wrong.
As I explained earlier, it is totally ethical to grow human organs in pigs:
Are such experiments really somehow inherently "damaging to our sense of humanity" or in violation of "something sacrosanct"? Nonsense. To make such claims is to confuse human organs and human DNA with human beings. A heart or liver is not a person, whether or not it is grown in a pig. And Human DNA is just the instructions on how to make a human body; it isn't a human body or brain.
To people worried that growing human organs animals somehow violates human dignity, bioethicist David Shaw asked the right question: "Is it dignified to let people suffer and die when we could use this new biotechnology to provide them with organs that will let them live long and happy lives?"
Congratulations to the Salk team.