Xenotransplantation – replacing human organs with ones from animals – has advanced since I reported last fall that the first pig kidney attached to a living human came from Iowa.

Doctors repeated the experiment at least twice, once at the University of Alabama at Birmingham on September 30, 2021 and again at New York University, which conducted the first kidney xenotransplant.

Then, in early January, University of Maryland Medical Center surgeons replaced a 57-year-old man’s failing heart with one from a genetically engineered pig. He has since died.

All the organs came from Revivicor, a division of medical conglomerate United Therapeutics. The first kidney transplanted at NYU came from a pig raised at an Iowa facility operated by Exemplar Genetics, a subsidiary of Sioux Center’s Trans Ova Genetics.

The pigs are engineered to remove three genes that would prompt a human body to reject the transplanted organ. Six human genes that Revivicor inserted into swine DNA are designed to help human bodies accept a transplanted organ.

The genetically modified pigs must be raised in medically conditions avoid exposing them to diseases hogs share with humans. Trans Ova subsidiary Exemplar specializes in providing such settings for research animals.

Although the first NYU kidney came from Iowa, it appears the other pig organs may have come from elsewhere. The Alabama pig was raised at the university. The New Yorker magazine notes that the heart transplanted in Maryland came from a Virginia facility.

Iowa may not have a monopoly on genetically modified hogs for transplant purposes, but the question remain: Is it ethical to turn animals into spare parts stores for humans?

Doctors turn to genetically engineered animals because there’s a persistent shortage of human donor organs. More than 100,000 Americans are on waiting lists, data from the Organ Procurement and Transplantation Network shows. Many will die before an appropriate organ is found.

That scarcity is a key factor in xenotransplantation ethical questions, said Dr. Paul J. Schenarts, a professor and associate dean at Des Moines University. Schenarts also is a professor in the Creighton University Department of Surgery and an intensive care unit doctor for the U.S. Department of Veterans Affairs medical system.

“Everybody understands there is an imbalance between organ availability and the need,” said Schenarts, who noted that his views on the subject are his own and not the institutions that employ him. Doctors and researchers have used various means to address that to disparity, but the donor organ supply is still short by about 60,000 per year in the United States.

Besides addressing an organ shortage, xenotransplantation may be the only option for some people, Schenarts said. Perhaps they had a failed heart transplant and their immune system is too degraded for a second. In other cases, an animal organ may provide a bridge, keeping a patient alive until another treatment is available or a human donor is found. Xenotransplants also are “advancing our medical knowledge and understanding of disease. I think that also has some benefits.”

Jason Ross, Iowa State University Lloyd Anderson Endowed Professor in Physiology and director of the Iowa Pork Industry Center, pointed out to me last year, pigs already provide replacement valves for heart patients and skin grafts for burn victims. We consume pigs for food – about 130 million a year, Ross said. “If there was a way to expand that into creating life-saving technologies for people, that’s excellent, right?” he added.

Schenarts agrees that xenotransplantation from food animals may be more acceptable than from from primates such as chimpanzees, but there are still complex ethical questions.

For example, there’s the question of informed consent: Patients receiving xenotransplants must know all the risks and benefits before they can agree to the operation. “Because of things we don’t know” about the consequences, “it is really almost impossible to give true informed consent to these procedures,” Schenarts said. Even for desperately ill people, “informed consent means we’re able to provide the patient a reasonable understanding of what is going to happen and we really don’t know” at present.

Among the unknowns is whether a xenotransplant recipient could unknowingly spread receiving an animal organ could animal-borne diseases. For example, viruses are embedded in pig DNA. These porcine endogenous retroviruses, or PERVs, are similar enough to human viruses that they can infect human cells, at least in the laboratory, said Christopher Tuggle, an animal science professor specializing in swine genetics.

That worries Schenarts. “It’s really hard to know … if any of these viruses are transmittable from the transplant recipient, say, to another person in public.” It’s a main reason he’s unsure if he would accept an animal organ transplant – that some unforeseen disease could spread to a family member. He also worries about the psychological impact – losing a sense of self, something human organ transplant recipients report.

“I’d have to know a bit more about it and more about what my condition is as I approached” a transplant, Schenarts said. For people with kidney failure, a replacement organ makes a huge improvement in their life over dialysis treatments. He believes xenotransplants and the knowledge necessary to do them are divine gifts, not “playing God,” an objection some people might raise. He’s not a vegetarian, so he has few qualms about using animal organs.

Yet, “I’m pretty torn” on the question, Schenarts admitted. “I don’t really have a truthful answer.”

The ISU swine experts I spoke to last fall had few qualms. “If it was going to save my life and I wasn’t able to get a human version,” a pig organ would be acceptable, Tuggle said ­– but the possibility of retrovirus exposure gives him pause, too.

Ross said he would take a pig organ, given the alternative. “We have people who die every single day due to needing an organ,” he added. A new heart, kidney, liver or other part, regardless of the source, would be “an excellent way to extend human life.”

While Schenarts finds raising animals to provide spare parts for humans, he understands why others, such as vegetarians or vegans, would be opposed. But splicing human DNA into the porcine genome raises another issue, Schenarts said: Now that it has human genes, “is the pig still a pig? Or is it some new being?” he asked. “People are pretty comfortable eating ham and pork chops, but I think the ethical piece here is very, very conflicted and confusing.”

Count me as conflicted, too. Reviewing my research, it occurs to me that I’ve heard from experts whose job it is to improve the animals we raise for slaughter and research and from an expert speaking from the perspective of patients and the doctors who treat them. But I haven’t yet found someone to speak for the animals.

I can’t help but recall “Hug,” an exhibition of works by Australian artist Patricia Piccinini that I saw at the Des Moines Art Center Downtown in 2007. Her super-realistic creations often explore the intersection of animal and human genetics.

One piece, “The Young Family,” stuck with me. You can see a detail of it here. The sculpture depicts a human-animal cross nursing her offspring, one of which plays, like a human infant, under her gaze. The exhibition notes described the mother’s demeanor as sad but accepting of her children’s fate: to provide transplant organs.

We’re not near that conundrum yet – and we needn’t be if we simply register as organ donors.