Ethical challenges of xenotransplantation

Abstract

The negative aspects of xenotransplantation are the high risk of organ rejection, which is greater when the genetic difference between animal and man is higher, as well as the transmission to the human being of zoonoses and retrovi- ruses that are potentially lethal, although they could be harmless in the animal donor. The risk of xenozoonoses to recipients and the general population is currently the main issue concerning the ethics of xenotransplantation. 2 Cur- rently, the transgenic pig is the most adequate species for organ donation and xenotransplantation. It breeds rapidly, its organs present approximately the same size and mor- phology as human organs, it is not endangered, it has been used for centuries in human alimentation, and pig heart valves and insulin have been used for several decades without problems. 2 Several studies are being conducted to assess the risk of transmission of infections from transgenic pigs to man. 3 The use of organs from nonhuman primates, although they pose a very low risk of hyperacute rejection (due to their phylogenetic closeness to humans), is re- stricted because of their slow breeding, the high costs involved in breeding them in a pathogen-free environment, the variability in the size of their organs, and the opposition of several animal rights activists like Peter Singer. 4 Further- more, the risk of transmission of microorganisms patho- genic to the human species is also higher and could lead to epidemics. 2 In our opinion, the clinical trials with porcine xenotrans- plants in human beings is ethically advisable despite their potential risks. The progress of medicine throughout the ages has always been associated with some degree of uncertainty and risk. As D. White says, if xenotransplan- tation can only be introduced into the clinic under condi- tions of zero tolerance of failure, then it is destined never to become a clinical reality. 3 That is in accordance with the conclusions of the serious report of the Nuffield Council on Bioethics and other institutions. 3,5 It is essential that the human recipients of xenotrans- plants give their informed consent to this new procedure, which excludes the involvement of those below the age of consent. They must be made aware of the risks involved, namely the possible transmission of infections, the potential benefits, and alternatives available. On the other hand, all recipients should be followed up closely. Furthermore, we propose that human clinical trials should start by gaining experience first, with the transplantation of organs such as the kidneys, before the use of vital organs such as the liver or heart. Therefore, we think that xenotransplantation, from an ethical point of view, represents a valid and defensible alternative to face the problem of the increasing shortage of organs available for transplantation. Meanwhile, we wait with interest for the results of the studies already in progress.