Controversial Chimera Research: Is This Little Piggy Really Part Human?

Scientists successfully injected human cells into a pig embryo early in its development.

(photo: Credit: ‘Bismoldirs’, CC BY-SA 4.0, via Wikimedia Commons)

On Friday, watching pro-life Americans march for Life in our nation's capital, I was invigorated at the thought that our country has embarked on a new course, respectful of human life from the moment of conception.

Then I read this: Just one day before, on Thursday, scientists on the West Coast announced that they have created the first successful human-animal hybrids.

At the Salk Institute in La Jolla, California, lead scientist Jun Wu and his team of researchers have injected human cells into a pig embryo early in its development. The resultant chimera – part pig and part human person – lived and grew for four weeks. Since government funding of the controversial research is prohibited, the project was privately funded.

In announcing the results this week, National Geographic seemed enthusiastic about future applications of this new scientific accomplishment. “Scientists hope,” said their report, “the chimera embryos represent key steps toward life-saving lab-grown organs.” 

According to National Geographic, human cells were injected into the pig embryos, and the embryos survived. Then they were put into adult pigs, which carried the embryos for between three and four weeks before they were removed and analyzed:

In all, the team created 186 later-stage chimeric embryos that survived, says Wu, and “we estimate [each had] about one in 100,000 human cells.”

But is this new application of science ethically permissible?

Rev. Tadeusz Pacholczyk, director of education at the National Catholic Bioethics Center, explained the controversy regarding human-animal hybrids in an article in February 2016, “Human Organs from Pigs: Is It Kosher?” He acknowledged that significant technical and ethical hurdles remain before growing organs in pigs is feasible; but he didn't rule out the possibility. In fact, he explained,

“Despite our initial hesitations, certain kinds of human/animal chimeras are likely to be justifiable and reasonable. This comes into focus when we recognize, for example, how thousands of patients who have received replacement heart valves made out of pig or cow tissues are already themselves a type of human/animal chimera.”

Father Tad concluded that

“...we should continue to insist that cutting edge biomedical research remain in active dialogue and interaction with sound ethics. The expanding study of human/animal chimeras challenges us to reflect carefully on the morally appropriate use of these novel and powerful technologies, so that human dignity will not be harmed, subjugated, or misappropriated in any way.”

National Institutes of Health Call for Public Comment on Chimera Research

Since 2009, the NIH's Guidelines for Human Stem Cell Research have specifically prohibited introducing human pluripotent cells into nonhuman primate blastocysts and the breeding of animals into which human pluripotent cells may have contributed to the germ line (egg or sperm cells). In September 2015, the NIH instituted a funding moratorium on research proposing to introduce human pluripotent cells into animal embryos prior to gastrulation stage—the beginning of development of the three germ layers. A workshop was organized in 2016; and in August 2016, the NIH issued a call for public comment regarding the scope of its chimera research.

NCBC Statement on Chimeras

In September 2016 the National Catholic Bioethics Center, along with other health care providers, ethicists and advocates for persons with disabilities, released an official statement on chimeras. Other signatories to the letter included the Catholic Medical Association, the National Catholic Partnership on Disability, the National Association of Catholic Nurses USA, the American Association of Pro-Life Obstetricians & Gynecologists, the Christian Medical and Dental Associations, and the American College of Pediatricians.

The statement was in response to proposed changes to the NIH Guidelines for Human Stem Cell Research and the Proposed Scope of an NIH Steering Committee’s Consideration of Certain Human-Animal Chimera Research. The full statement can be accessed at the NCBC website; but a few relevant points are:

  • Procedures related to chimera production must not involve the creation, destruction, or use of cellular derivatives from human embryos or directly-aborted human fetuses; human beings at these vulnerable stages must be safeguarded, not exploited, in both clinical and research settings. The use of induced pluripotent stem cells (iPSCs) or other sources of multipotent stem cells in chimera production could be ethically acceptable in research that does not conflict with the ethical issues identified below.
  • Human pluripotent stem cells or related derivatives should not be introduced into pre- or post-gastrulation non-human embryos unless the replication of major pillars of human identity can be avoided in the brain systems of those animals.

According to the scientists and ethicists at these Catholic and Christian organizations, a number of factors must be considered in evaluating the morality of chimera research. Depending on where the human cells originated, that new little piggy might not, in fact, be a shriekingly evil creation. If a child were aborted or killed in order to obtain the cells, then such a procedure would be abhorrent under Catholic theology. If, however, the cells were skin cells or other adult cells and if, by injecting the human cells into a  developing pig embryo, researchers could grow a human liver or kidney which would save a human life, such a procedure may be acceptable.

U.S. Bishops Strongly Oppose NIH Support for Chimera Research   

But the strongest language in opposition to funding chimera research comes from the U.S. Conference of Catholic Bishops. In August 2016, Greg Schleppenbach, Associate Director for the Bishops' Secretariat of Pro-Life Activities, issued a statement calling on Catholics to protest a new policy of the National Institutes of Health, which was planning to begin spending taxpayer dollars on chimera research. Schleppenbach wrote:

On August 4, 2016, the NIH announced that it was planning to begin spending taxpayer dollars on the creation and manipulation of new beings whose very existence blurs the line between humans and animals. We're not talking about using a pig's heart valve to fix a human heart. Nor are we talking about growing human cancer tumors in mice to study disease processes. These non-controversial practices have been going on for decades and don't pose any serious ethical problems.

The research NIH wants to fund is fundamentally different and ethically problematic for several reasons. First, it relies on the killing of humans at the embryonic stage to harvest their stem cells. Second, it involves the production of animals that could have partly or wholly human brains. Third, it involves the production of animals that could have human sperm or eggs (with a stipulation that precautions are taken so such animals are not allowed to breed).

Finally, introducing human embryonic stem cells into very early animal embryos will make it very difficult to know the extent to which human cells contribute to the final organism. This is another key moral problem with the NIH proposal: If researchers can't know for certain whether the resulting being has human status or characteristics, they won't know what their moral obligations may be toward that being.

Schleppenbach continued, protesting the NIH's oversight in failing to seriously consider the moral and ethical implications of the research, as well as other issues such as animal welfare. He wrote:

Furthermore, the NIH proposes to transcend this very serious ethical boundary apparently having given little, if any, consideration to the ethical and moral implications. When the NIH issued a moratorium on funding human-animal chimera research last September, it pledged to "undertake a deliberative process to evaluate the state of the science in this area, the ethical issues that should be considered, and the relevant animal welfare concerns associated with these types of studies" (emphasis added).

Yet in announcing its intention to rescind the moratorium on August 4, 2016, the NIH mentioned holding only one workshop, in November 2015, in order "to review the state of the science and discuss animal welfare issues." It mentioned nothing about any discussion of the "ethical issues" involved in creation and manipulation of partly human animals.

The Trump Administration, which has already signaled its pro-life agenda by supporting the March for Life and reinstating the Mexico City Policy, will need to consider whether U.S. tax dollars should be directed toward this controversial research.