thoughts on xenotransplantation

By Alison Campbell 30/09/2009 1

This is a re-post of one I wrote earlier this year. For a bit of background: one of the topics that year 13 Biology students can study requires them to do research around a ‘current’ or ‘controversial’ issue such as stem cells or xenotransplantation. I wrote a brief one on stem cells (really, more a case of pointing in the right direction), but then did a longer piece on xenotransplantation, which follows here.

The daughter said┬árecently that having done stem cells, I should also look at some of the other topics you can choose from for your research exercise. She suggested xenotransplantation, as it seems quite a few of her friends have chosen that one. So I’ll have a go ­čÖé

Xenotransplantation is where cells, tissues, or organs from an individual of one species are transplanted into an individual from another species. (‘Xeno-‘ means foreign; you see it also in the word ‘xenophobic’, meaning fear of foreigners.) One of the drivers for investigating xenotransplantation into humans is the fact that there is a global shortage of human organ donors, while the use of species such as pigs has the potential to provide an almost unlimited pool of organs. (My driving licence identifies me as a donor. But I”m fully aware that my wish to give any useful bits to others, after my death, might not be honored if members of my family objected to the idea. Hopefully they’ll respect my wishes. After all, the various bits & pieces will no longer be of any use to me!)

The first time I remember hearing about xenotransplantation back in 1984, although not, as I recall, using that specific name. It was the case of ‘Baby Faye’, who was born with hypoplastic left heart syndrome (the left side of the heart & the associated blood vessels are severely underdeveloped): doctors transplanted a baboon heart into the infant in an attempt to keep her alive until a suitable human donor became available. (However, this wasn’t the earliest case of xenotransplantation – it seems organ transplant┬á was first tried as far back as 1913, when doctors unsuccessfully transplanted a monkey kidney into a child whose kidneys had been damaged by mercury poisoning. Organs from baboons & other non-human primates have been used in transplants on several occasions, and it appears that frog skin was used in the late 1800s in treating patients needing skin grafts…)

Today the focus has shifted from primates to pigs. While the non-human primates are genetically closer to us, their organs are smaller – a baboon heart might do for a baby, but not an adult human! Nor can they be obtained in large numbers. Many primate species are under threat, or critically endangered. And many people would find it distasteful to consider killing other primates for the purpose of keeping humans alive.

Pigs, on the other hand, are closer to us in body size & mass, & are killed for food as it is, so it could be argued that taking organs for xenotransplantation would be less of a problem in ethical terms. Howver, pig organs are more likely to be rejected by their new host, & this has led to the idea of genetically engineering pigs so that they express human marker proteins on their cell membranes, instead of pig markers. This would reduce the likelihood of an extreme rejection reaction. And there are major concerns about the possibility of viral diseases, in particular, making the jump from pig to human via the new owner of the organs, although it’s been suggested that these could be reduced or eliminated in transgenic pigs.

But we also need to consider a range of other issues related to xenotransplantation. For example, people having Jewish or Muslum beliefs would probably find the idea of having pig tissues transplanted into them, quite abhorrent. Are there other cultural aversions to xenotransplants? What about the animals involved – do they suffer psychologically or physically before their deaths? Do we have the right to take their lives for this purpose? And the new ‘owner’ of the organ – would the presence of the xenotransplant alter them in some way? (There’s a Vatican document with a very thorough discussion of some of these ethical issues here.)

So, you can see that you’d got a lot to consider, if you chose this topic!

One Response to “thoughts on xenotransplantation”

  • The SMC did a briefing on this very subject earlier this year, where we got together a panel of three people knowledgeable in the area, including Bob Elliot, of Living Cell Technologies. It’s a particularly topical subject in NZ as the trials that LCT are conducting are a world-first, and, if successful, could give NZ the edge in developing technologies of these kinds.

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