Xenotransplantation is a term used to refer to the transplantation of organs between different species. Transplantation within human species (allotransplantation) has established an acceptable clinical role, especially involving organs such as the kidney, heart, bone marrow and liver. In fact, its success has caused demand to far outstrip supply. This is primarily due to shortage of available human donor organs. Many initiatives have been introduced such as publicity campaigns, distribution of donor cards, appointment of transplant co-ordinators, implementation of protocols in hospitals, and action programs for public and professionals. However, these have not been sufficient to increase the donor supply significantly. In 1993 in the United States alone, there were about 32,000 patients waiting for different organs . Most of these would either die or be severely incapacitated in the absence of a transplant.
As the programs become more successful, more recipients are identified, but the prospective increase in donors has lagged behind. The median waiting period for a number of various types of donor organs has also increased significantly over the last few years and continues to be a problem. Ethical Issues The search for suitable alternatives to donor organs has led to the intervention of xenotransplantation. Unlike allotransplantation, xenotransplantation is not an acceptable clinical procedure as yet and there are major scientific barriers in controlling the body’s ability to reject organs from different species. Ethical issues relating to xenotransplantation, therefore, involve not only whether xenotransplantation should be done, but whether any research should be carried out in this area if the perfected procedure would never be accepted on ethical grounds.
The primary ethical issues relating to xenotransplantation comprise: (1) those related to transplantation in general, and (2) the issue of animal sacrifice to obtain organs. With the evolution of transplantation many ethical issues have been identified. While most people are now satisfied with the definition of death from cerebral causes (“brain death”), there still is great ethical uncertainty in such areas as: ownership of cadaver organs; criteria for allocation of organs to those on waiting lists; surgery on health people as live donors of organs; abortion (and, allegedly, even abduction and murder of children for their organs, in certain parts of the world) in the ever more intensive search for viable replacement tissue. If solid organs were available from animal sources and their immunological rejection could be controlled, many of these ethical hazards would abate.
Animal studies have also reported problems from the likely transfer of pathogens such as viruses from donor to host, but these problems may also be solved, in time. The ethical argument against animal utilization is a complex issue and includes the controversy regarding the use of animals in medicine in general. 1. Animal Rights The first question is whether or not animals have rights. If so, are such rights clearly overridden by the rights of humans, or are these rights sufficient to make unacceptable animal sacrifice in the cause of medical science? In addition to the issue of animal rights, the question about duties of humans toward animals is also important. Should xenotransplantation, involving the intentional death of an animal, be considered before exhausting all the possibilities of human organ replacement or man-made devices?
Is there an ethical difference between using animals to solve unknown problems in the mechanism of human disease (many of which diseases also occur in animals, and their cure promotes veterinary medicine) and just dismantling animals for their organs? What are the ethical differences, if any, between using healthy animals for their organs and killing and consuming dead animals for our food? 2. Animals As Subjects for Human Ethical Concern There are some who view the debate between animal rights activists and those in the medical community mainly as a controversy of relative ethical importance: consequences (for humans) or rights (of animals).
Alternately, – dropping the issue of inherent animal rights – if animals are subjects for our ethical concern ,how does this valuation of their worth as living creatures measure up against the ways in which we can exploit them purely for our own ends? Certainly the argument used for employing xenotransplantation proposes that the loss of human life is ethically more significant than loss of animal life. To the supporters of xenotransplantation this seems a convincing answer. The duty to preserve human life justifies a xenograft. 3. “Speciesism” The opponents feel that there is no justification for ascribing to humans an absolute right to life to the exclusion of the rights to life of other creatures. Xenotransplantation is not morally acceptable because it elevates humans to an unjustifiably high status in the natural order, regardless of the human good which might come of it – such as preserving human life.
To do so is termed ‘speciesism’. 4. Endangerment of Survival of Higher Primates If xenotransplantation became successful it would open up opportunities for extended life to many patients. However, large numbers of animal sacrifices would have to be made. The impact of this would be particularly crucial if specific endangered primate species are utilised to meet the human demand for organs. The non-human primates, such as baboons, chimpanzees, monkeys, etc. are not available in large numbers. Their breeding is costly and their continued existence is endangered. These non-human primates are referred to as concordant species because the issues relating to rejection are not as complex as with discordant species. Control of massive rejection between widely differing species, such as pig to human or sheep to dog, poses major scientific hurdles which will involve costly research to overcome.
Whether such costs are justifiable in the face of lingering ethical questions is already a major issue. 5. The Lure of Scientific Acclaim Another important issue of professional ethics is ‘the kudos factor’, the fame which is attributed to `pioneers’ in a new field. There is a temptation to overstate research achievements in order to prematurely test new research possibilities in the clinical (human) setting. There never is a problem in obtaining volunteers when their life is already under threat, but how should they be protected from being subjects for premature innovation? There is concern that certain centres with vested interests may go ahead with this procedure without significant scientific justification. Will Research Ethics Boards have enough moral backbone to restrain this phenomenon, and how should they ensure this when potential subjects will also be pleading for the `one in a hundred’ chance to live?
6. Patients’ Acceptance of Whole Animal Organs by Transplantation Would a terminally ill patient resist having an intact organ of an animal placed in their body, even though they have been absorbing animals in molecular form from their digestive tract for years? This statement provokes the question of whether or not there is an ethical difference here? Some would evoke an `ethic of restraint’ which suggests that we should be very concerned about extending our biology in this way. However, the ethical arguments need to be developed more fully. Current Status In the last four to five years there has been a significant surge of interest in xenotransplantation and some of the people involved have come to grips with the realisation that non-human primates should not be used. Attention has been focused on an animal such as the pig which is already being sacrificed in large numbers for food consumption.
Pig heart valves have been used for the last 25 years and the ethical arguments against the use of a few thousand pigs each year for the purpose of transplantation have been muted. So far, research aimed at making xenotransplantation possible has had both ups and downs. All attempts to transplant whole animal organs, from the first operations in France in the 1900s to those in the US in the 1990s have failed. Optimism returned in 1994 when one biotech company showed that it was possible to genetically engineer pigs so that their organs could avoid immediate immune ejection if transplanted into a human. But the prospects soon worsened again as the risks of animal to human transplants became more apparent. All mammal species studied have a chromosomal region located identically.
The goal here was to develop strains of pigs whose organs would not induce a strong rejection in humans because the human immune system would `see’ human tissue groups on the pig organ. Meanwhile, a project into xenotransplantation is currently being undertaken as part of a European biomedical program and will focus on the ethical and social problems in early clinical trials of xenotransplantation (the unknown risk of virus infection from the xenograft and how to recruit participants in an ethical way), animal rights and animal welfare issues and the problem of social acceptance.
Following lengthy investigation of this subject, my views regarding the issue are, as yet, unclear. The arguments surrounding this issue are very much utilitarian and, as a result, one would need to take time to study and consider both viewpoints of the situation before reaching a valid conclusion. However, it appears reasonable that current research in xenotransplantation should continue at the experimental level preferably using a discordant model such as the pig.