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Xenotransplantation: Animal Organ Donors for Human Recipients

written by: Emma Lloyd • edited by: Leigh A. Zaykoski • updated: 11/27/2008

Animal organs transplanted into human bodies? Sounds impossible, but in fact it’s not at all far-fetched.

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    Xenotransplantation is the practice of transplanting cells, tissues, or organs, from one species to another. Generally, the term refers to the possibility of transplanting animal tissues and organs into humans.

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    Why use Animal Tissue?

    In many parts of the developed world, organ failure is a significant health issue. Another equally significant issue is that of the finite supply of replacement organs – many recipients spend years on a waiting list before receiving the donor organ they need. And 60% of people awaiting a donor organ die before receiving one.

    The solution, then, may lie in the possibility of using organs from other animals, in place of the human organs that are in such short supply. Thanks to recent advances in knowledge of the cause of transplant rejection, it may be possible to engineer animal-derived organs (most likely from pigs) to reduce the possibility of rejection occurring.

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    Problems with Xenotransplantation

    However, when it comes to transplant rejection, there’s a big problem: not only is the donor tissue genetically different from the recipient, it’s not even human. Transplanting human organs into human recipients is tricky enough – when the tissue comes from a different species, there are even more problems to contend with.

    The problem of immunological rejection is still the most pressing when it comes to xenotransplantation. The genetic differences between human and animal mean organ rejection is more likely to occur, and more likely to induce a severe reaction which may not only cause rejection of the organ, but may further endanger the life of the patient.

    Another possible issue is that infectious diseases may potentially spread from pigs to animals. Most of the world’s pigs are infected with porcine endogenous retroviruses – and the fear is that transplanting pig organs into humans may cause the spread of these viruses.

    Finally, there is the issue of acceptance, as there is plenty of opposition from animal rights groups who abhor the use of animals in medical science on ethical and moral grounds.

    And of course, there is the “ick factor” of using pig organs – however, recipients are not likely to be choosey when it comes to a possible life-saving tissue donation. There is a severe shortage of human donor organs and tissues, and if it comes to a choice between being one of the 60% who dies while waiting for an organ, and being someone who is alive and healthy—but with a pig-derived liver—which would you choose?