Xenotransplantation: Panacea or Pandora’s Box?

Editorial Team April 10th, 2012 1 Comment

pigIt would appear that not a week goes by without a revolutionary scientific advance coming to the fore of societal discussion – advances that seem inevitably, as mankind’s understanding of the very building blocks of nature expands, to be accompanied by ethical questions.

In short, are scientists too concerned about what they can achieve to stop to consider whether perhaps they should? Xenotransplantation, which is the transplantation of living cells, tissues or organs from one species to another, with the cells, tissues and organs in question referred to as xenografts or xenotransplants, is no exception, and is an innovation that is raising many novel medical, legal and ethical issues

While there appear to be few doubts that xenotransplantation could offer huge potential concerning the treatment of end-stage organ failure in humans, which is a significant health problem in many parts of the industrialised world, a major concern is that many of the animals used, including pigs in particular, have much shorter lifespans than humans, which means that their tissues age far more quickly. Given that the treatment is still very much in its infancy, this concern along with disease transmission (xenozoonosis) and even permanent alteration to the genetic code of animals are being cited by opponents as scientists archetypally ‘playing God’. While whole-organ xenografts have thus far been unsuccessful, less radical transplants have demonstrated great success. Hundreds of thousands of patients have received pig-heart valves since 1975, when the procedure first became commercially available. Cow-heart valves have likewise been used in humans since 1981.

Xenografts involving human beings have been a controversial procedure since they were first attempted by Dr. Keith Reemtsma between 1963 and 1964, in which 13 chimpanzee kidneys were transplanted into humans. Twelve of the 13 recipients died within two months, while the thirteenth survived for nine months after the procedure. Animal-rights groups in particular strongly oppose killing animals in order to harvest their organs for human use while certain religious beliefs, such as the Jewish and Muslim prohibition against eating pork, have been similarly problematic, however according to Council of Europe documentation, both religions agree that this rule is overridden by the preservation of human life.

Additional ethical issues include the informed consent complexities for research subjects, as well as the selection of human subjects, rights of patients and medical staff and public education (as companies may proceed with experiments without public awareness).

Obstacles arising from the response of the recipient’s immune system, specifically the rejection of the xenograft, which can in some cases result in the immediate death of the recipient. The types of rejection that xenograft patients face include hyperacute rejection, a rapid and violent type of rejection that occurs within minutes to hours from the time of the transplant, and is caused by the binding of XNAs (xenoreactive natural antibodies) to the donor endothelium, which activates the human complement system resulting in endothelial damage, inflammation, thrombosis and necrosis of the transplant.

On the other hand, a patient who is already very near to death because of a failing liver or heart is very likely to be willing to risk anything to save his or her life – does any animal-rights activist, no matter how sincere or well intentioned, have the right to deny such patients the chance to prolong their lives?

In addition, there is a worldwide shortage of organs for clinical implantation, with around 60% of patients awaiting replacement organs dying on the waiting list. In many cases there is so little chance of a person actually receiving a transplant, doctors do not even add the person to the list – is it not therefore reasonable to consider the engineering of organs from other species to attempt to minimize the risk of serious rejection, be used as an alternative to human tissues and possibly end organ shortages?

There can be no doubt that the issue is vexed. For readers who want to know more, a good, balanced account of the pros and cons is provided by the following lecture on YouTube, while The Future of Healthcare in Europe, a report released as part of the European Commission’s Europe 2020 Strategy, also raises some interesting questions on xenotransplantation.

Clearly Xenotransplantation has a lot of room for improvement, but should we be doing it at all? What’s your view?

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