What are the ethical issues with pig-to-human transplants?

Xenotransplantation and the modern medical era

September 29, 2022

Pig-to-human transplants sounds like science fiction, but actual occurrences of this experimental treatment were in medical news earlier this year. The field is known as xenotransplantation and refers to any sort of cross-species transplant. While there have been documented attempts at xenotransplantation as far back as the 17th century, with advancements in medicine and science in the modern era, xenotransplantation has become a reality with clinical trials of solid organs (e.g., kidneys; hearts) likely to take place soon. Christians should think carefully through the ethical issues this aspect of the medical world brings to the forefront.  

Why are pigs being used in humans?

The demand for human organs for transplant always outpaces their supply. In the United States alone there are over 100,000 persons waiting on an organ. The vast majority of these are waiting on a kidney, where the median wait time is about 3.5 years. Many patients will die from end-stage organ failure or other complications before they ever receive a transplant. To help mitigate this disparity, alternative sources of organs have been experimented with for decades. 

One alternative source that has shown a lot of promise in pre-clinical trial studies is genetically-altering pigs in order to make their organs more compatible for human use. Other animals have been considered, and xenotransplants have been attempted with them. A famous case—known as Baby Fae—took place in 1984. An infant only days old with a severe heart abnormality received a baboon heart. The child would die three weeks post-transplant from organ rejection. Since then, the primary model for solid organ xenotransplantation has shifted from primates to pigs for several reasons, including the large litter size of pigs, the size of pig organs that are roughly compatible with humans, the lesser risk of infectious disease transfer, and many persons seem to have less issue with using pigs than primates—though the use of pigs is still contested.

What are the latest advancements in xenotransplantation? 

Xenotransplantation has been primarily in pre-clinical trial stages for years. Researchers have been doing genetic alterations on the pig genome to make the organs more compatible with humans. Without these modifications of the pig genome then, even with immunosuppressant medication, it is likely that hyperacute rejection would soon occur—a process in which the body thinks something is foreign and attacks it. In addition to genetic modifications, work has been ongoing on novel immunosuppressant therapy as well as experiments that place the genetically-altered pig organs into other mammals, such as baboons, to see how they respond. 

In the fall of 2021, New York University (NYU), under the leadership of Robert Montgomery, transplanted a pig kidney into a human recipient that had been declared deceased by brain death criteria. Then they did it again about two months later.1Montgomery RA, Stern JM, Lonze BE, et al. Results of Two Cases of Pig-to-Human Kidney Xenotransplantation. N Engl J Med. 2022;386(20):1889-1898. Shortly after the first transplant at NYU, Jayme Locke and her team at the University of Alabama at Birmingham (UAB) transplanted two kidneys from a genetically-altered pig into a brain-dead human.2Porrett PM, Orandi BJ, Kumar V, et al. First clinical-grade porcine kidney xenotransplant using a human decedent model. Am J Transplant. 2022;22(4):1037-1053. Both research teams reported that the kidneys seemed to function fairly well, and there was no sign of hyperacute rejection. 

While the kidney transplants in brain-dead humans were a step forward for xenotransplantation, a giant leap would follow. The University of Maryland Medical Center (UMMC) would stun the transplant community when they announced in early January 2022 that they had successfully transplanted a pig heart into a living human.3Kotz D. UM Medicine Performs Historic Xenotransplantation. https://www.umaryland.edu/news/archived-news/january-2022/um-medicine-performs-historic-xenotransplantation.php. Published 2022. Updated January 11, 2022. Accessed January 12, 2022. The patient—David Bennett, Sr.—was reportedly not a candidate for a human heart. UMMC had a longstanding research program into pig heart transplantation and researchers at UMMC asked the U.S. Food and Drug Administration for emergency authorization to allow them to transplant a pig heart into Bennett. He would live for over 8 weeks4Rothblatt M. Commentary on achievement of first life-saving xenoheart transplant. Xenotransplantation. 2022:e12746. before dying from what some have suspected to be a virus that was transferred to him from the pig heart.

What are the ethical issues involved in xenotransplantation for Christians to be aware of?

While allotransplantation (human-to-human transplants) has been written on from a Christian perspective for decades (Helmut Thielicke, Paul Ramsey, and Gilbert Meilaender to name a few), Christian writings on xenotransplantation are sparse. The Catholic Church’s Pontifical Academy for Life has developed perhaps the most comprehensive theological viewpoint on the subject that would likely resonate with many Protestant Christians. Additional symposia and focus groups have been conducted with academic theologians and clergypersons alike,5Hurst DJ, Padilla LA, Cooper DKC, Paris W. Factors influencing attitudes toward xenotransplantation clinical trials: a report of focus group studies. Xenotransplantation. 2021:e12684. 6Paris W, Seidler RJH, FitzGerald K, Padela AI, Cozzi E, Cooper DKC. Jewish, Christian and Muslim theological perspectives about xenotransplantation. Xenotransplantation. 2018;25(3):e12400.and there has been a small number of empirical studies looking at how religious persons view xenotransplantation. 

From my perspective, the most glaring ethical issues with xenotransplantation that we need to think through from a theological perspective are 1) the use of animals as a supply of organs, and 2) the potential risk of infectious disease and how this may impact those who receive a pig organ and the wider public. Each of these two items has many subpoints that will be explained.

The proper use of animals for the benefit of humans has long been the subject of deliberation. In the Genesis creation account, God states, “Let us make man in our image, after our likeness. And let them have dominion over the fish of the sea and over the birds of the heavens and over the livestock and over all the earth and over every creeping thing that creeps on the earth” (Gen. 1:26, ESV). From this account, it seems unquestionable that God gives humankind dominion over other living things, yet what this dominion entails has been subject to interpretation. 

Scripture reveals that God allows animals to be used for the benefit of humans in a variety of ways, including as food (Gen. 9:3), clothing (Gen. 3:21), and for labor that benefits humankind (Exo. 23:12). The term stewardship is often used when Christians think through their relationship to the created world, including animals (i.e., God has appointed humans as stewards over his creation). While in the garden of Eden prior to sin entering the human realm, Adam’s role in the garden is “to work it and keep it” (Gen. 2:15). A conventional interpretation of this implies that humans (Adam, in particular) are given a leadership role over God’s created role to prepare it, guard it, and protect it. King David tells us that all of creation is God’s: “The earth is the LORD’s and the fullness thereof, the world and those who dwell therein” (Psa. 24:1). All of creation is the Lord’s, and he has given a leadership role over his creation to humans, a delegation of authority to steward the world, its resources, and the living creatures within. 

How should we think about xenotransplantation? 

With these items in mind, how then do we regard xenotransplantation? I will emphatically note that Christian liberty instructs that we can disagree over the conclusions we draw from what it means to be stewards of God’s created world. Yet, I think there is a convincing argument that as God has granted dominion over the created world to humans, and as humans are meant to steward those resources well, then xenotransplantation may fit within this framework if we maintain certain parameters.

First, Christian doctrine affirms that humans are the only beings created in God’s image and, by bearing that image, they occupy a place of importance in the created order that animals do not. Humans are the ultimate work of creation. As the pinnacle of creation, some have taken this to mean that humankind can do anything they please with other created entities (e.g., the environment, animals). This would be a misinterpretation of what it means to be a steward of the resources God has given to humankind. Surely abuses have occurred in the past and present in the name of so-called exercising dominion, but acting in God’s image means—in part—that we are to mirror his goodness for creation. Christians can differ in how we apply certain aspects of dominion, such as what sound environmental policy might entail, but seeing the created world as merely at the disposal of humans and to be used in any conceivable way would be mistaken. 

While we must not make the mistake of seeing the created as ours to be exploited, one purpose of the created world is for the use—even the flourishing—of humanity. I am sensitive to those who have hesitations about explicitly breeding a genetically altered species of pigs solely for the purpose of using their organs to meet human needs. Yet, we similarly breed species of animals for other purposes: for sport, for work, for food, for companionship. These activities, it could be argued, are for human flourishing. Hence, if we deem it acceptable to promote the use of animals for these purposes, then it does not seem that using an animal for xenotransplantation is entirely dissimilar. This is not to say we still do not try to promote such activities within the confines of what is ethical (e.g., try to reduce animal suffering; reduce the number of animals needed if possible), but there does not seem to be anything explicitly unethical about the use of animals for the purpose of xenotransplantation if we accept the use of animals for certain other purposes. 

Second, one risk of xenotransplantation that has been known for decades is xenozoonotic infection. That is, the risk that the nonhuman organ may contain an infectious disease, such as a virus, that could infect the human that receives the nonhuman organ. It is then plausible that such an infection could spread to other close contacts and become a public health concern. As it was recently reported that the pig heart transplanted into the patient at UMMC was infected with a pig virus, this is a serious issue. Steps have been taken to reduce the risk of a xenozoonotic infection being transferred from a pig to a human, such as research protocols aimed at supplying pathogen-free porcine specimens (i.e., in how they’re raised/prepared), as well as developing highly sensitive molecular diagnostic panels to screen xenotransplant material for a wide range of infectious agents immediately prior to the transplant procedure. 

However, even with this mitigation the risk still exists, and the true level of this risk is uncertain. Every day, we accept some level of risk for ourselves and those around us. We drive our cars and are accepting risk. If we have passengers—children, especially—we are accepting a risk for them, as they cannot consent to that risk. I bring up the aspect of “risk” because as Christians we are called to love our neighbors. Jesus speaks of the greatest commandments being to love him and love our neighbor. Accepting a nonhuman organ carries the risk of becoming infected with a pig virus and then possibly exposing others (our neighbor) to that risk—a risk they did not consent to accept. From an ethical perspective, even apart from the question of how Christians might view xenotransplantation, the risk of infectious disease is likely the most looming ethics issue facing this new therapy. In one sense, putting our neighbor at some risk is unavoidable in this world. More work certainly needs to be done to ensure that the pigs used for xenotransplantation are pathogen-free, which would undoubtedly ease the minds of many.  

In short, xenotransplantation does present ethical challenges, but none seem outright insurmountable. The largest ethical issue facing xenotransplantation is the risk of potential infectious disease and what this may entail. For instance, some proposals call for xenograft recipients to be monitored for infectious diseases for the remainder of their lives. This seems difficult for both the study sponsor and the graft recipient to realize. The constant risk of spreading an infectious disease to loved ones (at least until the scientific community can be certain their source pigs are indeed pathogen-free) is a glaring issue and one that Christians may not want to assume currently. 

Acknowledgment: I want to thank long-time friend Scott James, MD for reading an early draft of this article and offering many helpful comments. 

Potential conflicts of interest: DJH is a paid consultant to a working group on ethical and social viewpoints of xenotransplantation at NYU. 

Daniel J. Hurst

Daniel J. Hurst is director of Medical Professionalism, Ethics, and Humanities and assistant professor in the Department of Family Medicine at Rowan University School of Osteopathic Medicine in Stratford, New Jersey. He was previously on the faculty at UAB where he was involved in the xenotransplantation program performing studies on … Read More

Article 12: The Future of AI

We affirm that AI will continue to be developed in ways that we cannot currently imagine or understand, including AI that will far surpass many human abilities. God alone has the power to create life, and no future advancements in AI will usurp Him as the Creator of life. The church has a unique role in proclaiming human dignity for all and calling for the humane use of AI in all aspects of society.

We deny that AI will make us more or less human, or that AI will ever obtain a coequal level of worth, dignity, or value to image-bearers. Future advancements in AI will not ultimately fulfill our longings for a perfect world. While we are not able to comprehend or know the future, we do not fear what is to come because we know that God is omniscient and that nothing we create will be able to thwart His redemptive plan for creation or to supplant humanity as His image-bearers.

Genesis 1; Isaiah 42:8; Romans 1:20-21; 5:2; Ephesians 1:4-6; 2 Timothy 1:7-9; Revelation 5:9-10

Article 11: Public Policy

We affirm that the fundamental purposes of government are to protect human beings from harm, punish those who do evil, uphold civil liberties, and to commend those who do good. The public has a role in shaping and crafting policies concerning the use of AI in society, and these decisions should not be left to those who develop these technologies or to governments to set norms.

We deny that AI should be used by governments, corporations, or any entity to infringe upon God-given human rights. AI, even in a highly advanced state, should never be delegated the governing authority that has been granted by an all-sovereign God to human beings alone. 

Romans 13:1-7; Acts 10:35; 1 Peter 2:13-14

Article 10: War

We affirm that the use of AI in warfare should be governed by love of neighbor and the principles of just war. The use of AI may mitigate the loss of human life, provide greater protection of non-combatants, and inform better policymaking. Any lethal action conducted or substantially enabled by AI must employ 5 human oversight or review. All defense-related AI applications, such as underlying data and decision-making processes, must be subject to continual review by legitimate authorities. When these systems are deployed, human agents bear full moral responsibility for any actions taken by the system.

We deny that human agency or moral culpability in war can be delegated to AI. No nation or group has the right to use AI to carry out genocide, terrorism, torture, or other war crimes.

Genesis 4:10; Isaiah 1:16-17; Psalm 37:28; Matthew 5:44; 22:37-39; Romans 13:4

Article 9: Security

We affirm that AI has legitimate applications in policing, intelligence, surveillance, investigation, and other uses supporting the government’s responsibility to respect human rights, to protect and preserve human life, and to pursue justice in a flourishing society.

We deny that AI should be employed for safety and security applications in ways that seek to dehumanize, depersonalize, or harm our fellow human beings. We condemn the use of AI to suppress free expression or other basic human rights granted by God to all human beings.

Romans 13:1-7; 1 Peter 2:13-14

Article 8: Data & Privacy

We affirm that privacy and personal property are intertwined individual rights and choices that should not be violated by governments, corporations, nation-states, and other groups, even in the pursuit of the common good. While God knows all things, it is neither wise nor obligatory to have every detail of one’s life open to society.

We deny the manipulative and coercive uses of data and AI in ways that are inconsistent with the love of God and love of neighbor. Data collection practices should conform to ethical guidelines that uphold the dignity of all people. We further deny that consent, even informed consent, although requisite, is the only necessary ethical standard for the collection, manipulation, or exploitation of personal data—individually or in the aggregate. AI should not be employed in ways that distort truth through the use of generative applications. Data should not be mishandled, misused, or abused for sinful purposes to reinforce bias, strengthen the powerful, or demean the weak.

Exodus 20:15, Psalm 147:5; Isaiah 40:13-14; Matthew 10:16 Galatians 6:2; Hebrews 4:12-13; 1 John 1:7 

Article 7: Work

We affirm that work is part of God’s plan for human beings participating in the cultivation and stewardship of creation. The divine pattern is one of labor and rest in healthy proportion to each other. Our view of work should not be confined to commercial activity; it must also include the many ways that human beings serve each other through their efforts. AI can be used in ways that aid our work or allow us to make fuller use of our gifts. The church has a Spirit-empowered responsibility to help care for those who lose jobs and to encourage individuals, communities, employers, and governments to find ways to invest in the development of human beings and continue making vocational contributions to our lives together.

We deny that human worth and dignity is reducible to an individual’s economic contributions to society alone. Humanity should not use AI and other technological innovations as a reason to move toward lives of pure leisure even if greater social wealth creates such possibilities.

Genesis 1:27; 2:5; 2:15; Isaiah 65:21-24; Romans 12:6-8; Ephesians 4:11-16

Article 6: Sexuality

We affirm the goodness of God’s design for human sexuality which prescribes the sexual union to be an exclusive relationship between a man and a woman in the lifelong covenant of marriage.

We deny that the pursuit of sexual pleasure is a justification for the development or use of AI, and we condemn the objectification of humans that results from employing AI for sexual purposes. AI should not intrude upon or substitute for the biblical expression of sexuality between a husband and wife according to God’s design for human marriage.

Genesis 1:26-29; 2:18-25; Matthew 5:27-30; 1 Thess 4:3-4

Article 5: Bias

We affirm that, as a tool created by humans, AI will be inherently subject to bias and that these biases must be accounted for, minimized, or removed through continual human oversight and discretion. AI should be designed and used in such ways that treat all human beings as having equal worth and dignity. AI should be utilized as a tool to identify and eliminate bias inherent in human decision-making.

We deny that AI should be designed or used in ways that violate the fundamental principle of human dignity for all people. Neither should AI be used in ways that reinforce or further any ideology or agenda, seeking to subjugate human autonomy under the power of the state.

Micah 6:8; John 13:34; Galatians 3:28-29; 5:13-14; Philippians 2:3-4; Romans 12:10

Article 4: Medicine

We affirm that AI-related advances in medical technologies are expressions of God’s common grace through and for people created in His image and that these advances will increase our capacity to provide enhanced medical diagnostics and therapeutic interventions as we seek to care for all people. These advances should be guided by basic principles of medical ethics, including beneficence, non-maleficence, autonomy, and justice, which are all consistent with the biblical principle of loving our neighbor.

We deny that death and disease—effects of the Fall—can ultimately be eradicated apart from Jesus Christ. Utilitarian applications regarding healthcare distribution should not override the dignity of human life. Fur- 3 thermore, we reject the materialist and consequentialist worldview that understands medical applications of AI as a means of improving, changing, or completing human beings.

Matthew 5:45; John 11:25-26; 1 Corinthians 15:55-57; Galatians 6:2; Philippians 2:4

Article 3: Relationship of AI & Humanity

We affirm the use of AI to inform and aid human reasoning and moral decision-making because it is a tool that excels at processing data and making determinations, which often mimics or exceeds human ability. While AI excels in data-based computation, technology is incapable of possessing the capacity for moral agency or responsibility.

We deny that humans can or should cede our moral accountability or responsibilities to any form of AI that will ever be created. Only humanity will be judged by God on the basis of our actions and that of the tools we create. While technology can be created with a moral use in view, it is not a moral agent. Humans alone bear the responsibility for moral decision making.

Romans 2:6-8; Galatians 5:19-21; 2 Peter 1:5-8; 1 John 2:1

Article 2: AI as Technology

We affirm that the development of AI is a demonstration of the unique creative abilities of human beings. When AI is employed in accordance with God’s moral will, it is an example of man’s obedience to the divine command to steward creation and to honor Him. We believe in innovation for the glory of God, the sake of human flourishing, and the love of neighbor. While we acknowledge the reality of the Fall and its consequences on human nature and human innovation, technology can be used in society to uphold human dignity. As a part of our God-given creative nature, human beings should develop and harness technology in ways that lead to greater flourishing and the alleviation of human suffering.

We deny that the use of AI is morally neutral. It is not worthy of man’s hope, worship, or love. Since the Lord Jesus alone can atone for sin and reconcile humanity to its Creator, technology such as AI cannot fulfill humanity’s ultimate needs. We further deny the goodness and benefit of any application of AI that devalues or degrades the dignity and worth of another human being. 

Genesis 2:25; Exodus 20:3; 31:1-11; Proverbs 16:4; Matthew 22:37-40; Romans 3:23

Article 1: Image of God

We affirm that God created each human being in His image with intrinsic and equal worth, dignity, and moral agency, distinct from all creation, and that humanity’s creativity is intended to reflect God’s creative pattern.

We deny that any part of creation, including any form of technology, should ever be used to usurp or subvert the dominion and stewardship which has been entrusted solely to humanity by God; nor should technology be assigned a level of human identity, worth, dignity, or moral agency.

Genesis 1:26-28; 5:1-2; Isaiah 43:6-7; Jeremiah 1:5; John 13:34; Colossians 1:16; 3:10; Ephesians 4:24