History (Genetics & Inherited Conditions)
The idea of xenotransplants is actually quite old. During the eighteenth century, for example, transfusions of sheep’s blood were believed to be therapeutic for certain human illnesses. As the science of organ transplants between humans progressed, researchers became increasingly interested in experimenting with using animals as donors. Organ transplantation became an accepted medical treatment in humans, but there are not enough donor organs from humans available to treat every patient who could benefit from the procedure. In 2006, more than 98,000 people in the United States were waiting for an organ. As the demand for transplant surgery grows, the pool of available donor organs shrinks in relation. One of the ethical dilemmas inherent in human organ transplant is that, in most cases, for one person to receive a transplant, another person must die. Bone marrow, partial liver, and kidney transplants are among the few exceptions; donors can usually donate bone marrow, a lobe of their liver, or one kidney and still survive. Nevertheless, for most organs the dilemma remains.
Researchers are interested in using organs harvested from compatible animals, eliminating both the need to wait for a compatible human donor and the shortage of usable organs. This is one form of xenotransplant, and it could eliminate the shortage of donor organs. However, researchers have encountered two major barriers to xenotransplantation; organ rejection by...
(The entire section is 712 words.)
Transgenic Pigs (Genetics & Inherited Conditions)
In 1992, researchers in the United Kingdom announced the creation of Astrid, the first transgenic pig. A transgenic animal is one who has been genetically modified with genes from another species. Since then, several groups have worked to create pigs with organs that have been genetically modified to be human compatible so that they are not rejected by the human immune system. Another goal of this kind of research is to create pigs with organs that are not susceptible to pig viruses.
(The entire section is 81 words.)
Ethical and Medical Concerns (Genetics & Inherited Conditions)
Xenotransplantation presents a number of ethical and medical dilemmas. The possibility that a virus, harmless to the donor animal, might be transmitted to the human host and then prove fatal is a major concern. Scientists worry that a potentially deadly disease epidemic could result from using organs or other tissue from either swine or primates. While many researchers are confident that careful screening of donor animals would eliminate or minimize such risks, critics remain convinced that it is possible a virus could lie dormant and undetected in animals, causing problems only after the transplants occurred. Baboons, for example, carry a virus that has the potential to cause cancer in humans.
In addition to the medical issues raised, many bioethicists question the morality of using animals as a source of “spare parts” for humans. They are particularly troubled by the idea of genetically altering a species such as swine in order to make their organs more compatible with human hosts. Proponents of xenotransplants counter these arguments by noting that humans have selectively bred animals for various purposes for thousands of years to eliminate certain characteristics while enhancing others. In addition, animals such as swine are already routinely slaughtered for human consumption.
Finally, there is the problem of human perceptions. While many people support the idea of xenotransplants on the genetic or...
(The entire section is 309 words.)
Impact (Genetics & Inherited Conditions)
An immediate and plentiful source of organs from swine could improve and save many human lives. Overcoming the immunological problems and infectious disease risks are serious barriers to xenotransplantation, and remain active areas of research. Creating transgenic pigs with human-compatible organs is a main thrust of research in xenotransplantation. However, human stem cells from unused embryos or adult stem cells is a competing line of research that may offer an alternative source of organs for transplantation, or a means to repair diseased ones.
(The entire section is 83 words.)
Further Reading (Genetics & Inherited Conditions)
Bassett, Pamela. Emerging Markets in Tissue Engineering: Angiogenesis, Soft and Hard Tissue Regeneration, Xenotransplant, Wound Healing, Biomaterials, and Cell Therapy. Southborough, Mass.: D & MD Reports, 1999. Looks at xenotransplants from an economic perspective and discusses the potential for growth for biomedical firms entering the field.
Bloom, E. T., et al. “Xenotransplantation: The Potential and the Challenges.” Critical Care Nurse 19 (April, 1999): 76-83. Looks at the potential impact of xenotransplantation on patient care as well as the effects it might have on nursing responsibilities.
Boneva, R. S., and T. M. Folks. “Xenotransplantation and Risks of Zoonotic Infections.” Annals of Medicine 36 (2004): 504-517. Reviews infectious disease risks associated with xenotransplantation.
Cruz, J., et al. “Ethical Challenges of Xenotransplantation.” Transplant Proceedings 32 (December, 2000): 2687. Members of a medical transplant team discuss questions about potential moral contradictions in using animal organs in human patients.
Daar, A. S. “Xenotransplants: Proceed with Caution.” Nature 392 (March 5, 1998): 11. Sounds a warning about some of the potential risks involved in xenotransplants.
Ghebremariam, Y. T., et al. “Intervention Strategies and Agents Mediating the Prevention of Xenorejection.” Annals of the New York...
(The entire section is 299 words.)