xenotransplantation

It has been suggested that Organ xenotransplantation be merged into this article or section. (Discuss)

Xenotransplantation (xeno- from the Greek meaning "foreign") is the transplantation of living cells, tissues or organs from one species to another, such as from pigs to humans (see medical grafting). Such cells, tissues or organs are called xenografts or xenotransplants. The term allotransplantation refers to a same-species transplant. Human xenotransplantation offers a potential treatment for end-stage organ failure, a significant health problem in parts of the industrialized world. It also raises many novel medical, legal and ethical issues.^[1] A continuing concern is that pigs have shorter lifespans than humans: their tissues age at a different rate. Disease transmission (xenozoonosis) and permanent alteration to the genetic code of animals are also causes for concern. There are few published cases of successful xenotransplantation.^[2]

Because there is a worldwide shortage of organs for clinical implantation, about 60% of patients awaiting replacement organs die on the waiting list. Recent advances in understanding the mechanisms of transplant rejection have brought science to a stage where it is reasonable to consider that organs from other species, probably pigs, may soon be engineered to minimize the risk of serious rejection and used as an alternative to human tissues, possibly ending organ shortages. Other procedures, some of which are being investigated in early clinical trials, aim to use cells or tissues from other species to treat life-threatening and debilitating illnesses such as cancer, diabetes, liver failure and Parkinson's disease. If vitrification can be perfected, it could allow for long-term storage of xenogenic cells, tissues and organs so that they would be more readily available for transplant.

Xenotransplants could save thousands of patients waiting for donated organs. The animal organ, probably from a pig or baboon could be genetically altered with human genes to trick a patient’s immune system into accepting it as a part of its own body. They have re-emerged because of the lack of organs available and the constant battle to keep immune systems from rejecting allotransplants. Xenotransplants are thus potentially a more effective alternative.

Xenozoonosis and rejection

Besides facing possible rejection, xenotransplants could potentially transmit animal diseases to humans and result in epidemics. Baboons and pigs carry myriad transmittable agents which are harmless in their natural host but extremely toxic and deadly in humans. HIV is an example of a disease which is believed to have jumped from monkeys to humans. Researchers also do not know if an outbreak of infectious diseases could occur and if they could contain the outbreak even though they have measures for control. Another obstacle facing xenotransplants is that of the body’s rejection of foreign objects by its immune system. These antigens (foreign objects) are often treated with powerful immunosuppressive drugs which could in turn make the patient vulnerable to other infections and actually aid the disease trying to be cured. This is the reason the organs would have to be altered to fit with the patients DNA (histocompatibility).

In 2005, the Australian National Health and Medical Research Council declared a eighteen-year moratorium on all animal-to-human transplantation, concluding that the risks of transmission of animal viruses to patients and the wider community have not yet been resolved.^[3]

Ethicality

This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2009)

Xenografts have been a controversial procedure since they were first attempted. Many, including animal rights groups, strongly oppose killing animals in order to harvest their organs for human use. Medical concerns exist about possible disease transfer between animals and humans, such as the porcine endogenous retrovirus found in pig tissues. Religious beliefs, such as the Jewish and Muslim prohibition against eating pork, have been sometimes thought to be a problem, however according to a Council of Europe documentation both religions agree that this rule is overridden by the preservation of human life. In general, the use of pig and cow tissue in humans has been met with little resistance, save some religious beliefs.

The main ethical issues associated with xenotransplants are that the animals which would be commonly used for their organs, such as pigs and baboons are killed or sacrificed. Baboons are very similar to humans with human-like hands, faces and a developed social structure. For this reason pigs could be used more as their anatomies are similar to humans and are a lot easier to breed than baboons that only produce one offspring at a time. Pigs are also a lot healthier and carry less disease than primates as well. There are fewer moral objections to the killing of pigs as they are already killed for food and are already being produced.

See also

• Allograft
• Medical grafting
• Organ xenotransplantation
• Xenographic
• Xenopregnancy

References

External links

Look up xenotransplantation in Wiktionary, the free dictionary.

• PBS Special on Pig to Human Transplants
• Uncaged Campaigns
• Diaries of Despair
• Campaign for Responsible Transplantation
• Xenotransplantation: Risks, Clinical Potential, and Future Prospects Robert E. Michler, 1996
• The Australian National Health and Medical Research Council's 2005 statement on xenotransplantation
• [1] Snapshots of Science and Medicine: Xenotransplantation
• Jorge Guerra González: Infection Risk and Limitation of Fundamental Rights by Animal-To-Human Transplantations. EU, Spanish and German Law with Special Consideration of English Law. Verlag Dr. Kovac, Hamburg 16 November 2009, ISBN 978-3-8300-4712-4.