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What Is Xenotransplantation?

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  1. Where are the human genes coming from that are inserted? Is aborted human fetal tissue being used?  
  2. What is the quality of life of the human-pig chimera that has been created solely for eventual sacrifice for its organs?
  3. What risk will the transplant recipient face of becoming ill from endogenous pig viruses, especially as he/she will need anti-rejection drugs and be immunodeficient for the rest of his or her life?

If the human genes being inserted are coming from an ethical source, AND the pig-human chimera is as comfortable as any other lab animal, AND animal viruses are not going to be an issue (a lot to assume) this new technology MAY be acceptable. Certainly, it would be preferable to the murder of vulnerable people (as with donation after 'brain death' or 'circulatory death') who are actually alive at the time of their organ harvests.

In August, 2023 two 'brain dead' men were used as test subjects when researchers at the University of Alabama and the NYU Langone Transplant Institute surgically implanted genetically modified pig kidneys were into their abdomens. (A similar surgery had been performed the previous year, but the kidney did not function successfully.) This time around, one helpless 'brain dead' man has been kept alive like a lab rat for over a month as doctors study how long the xenotransplanted kidney will function. 

It is hard to imagine that an experiment of this nature would receive consent from not only the family, but also the institutional review boards and ethics committees of these respective hospitals. When the President's Council on Bioethics wrote their white paper on death determination in 2008, they morally justified the declaration of death by neurologic criteria ('brain death') on the basis that continuing to ventilate and support these people violated the respect due to the 'dead'. Clearly, that respect has now gone out the window in the never-ending quest for more transplantable organs. 

And the experimentation continues. In March, 2024, Chinese scientists transplanted the liver of a gene-edited pig into a 'brain dead' human. Researchers at the Chengdu-based Clonorgan Biotechnology firm removed three pig antigens from the donor animal using gene-editing technology, and replaced them with three human proteins. Team leader Dou Kefeng said that because liver functions are complex, gene-edited pig livers cannot completely replace human livers at present. The experiment "provides a theoretical basis and data support for the clinical application of xenotransplantation," he added.

On March 16, 2024, doctors at Massachusetts General Hospital placed another genetically modified pig kidney into a human recipient. According to the press release, the pig kidney was provided by eGenesis of Cambridge, Mass., from a pig donor that was genetically-edited using CRISPR-Cas9 technology to remove harmful pig genes and add certain human genes to improve its compatibility with humans. Additionally, scientists inactivated porcine endogenous retroviruses in the pig donor to eliminate any risk of infection in humans. The patient, 62-year-old Mr. Richard ‘Rick’ Slayman of Weymouth, Mass., is recovering well at MGH and is expected to be discharged soon.


Historically, xenotransplant, or the transplantation of organs from other species to humans, has failed due to incompatibility and rejection. Recently, an American patient became the first to receive a genetically modified pig heart transplant. The donor pig had undergone deletion of certain pig genes and addition of human genes to make its heart less likely to be recognized as foreign by the human recipient. David Bennett Sr. lived 45 days before apparently dying of a pig virus that hitched a ride on his new heart.

Time will tell how well this technology will work, but several moral questions arise:

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