Are pig-human chimeras the future of transplantation?

Are pig-human chimeras the future of transplantation?

Tonight the BBC will be airing a documentary about xenotransplantation – in this case, the growth of human organs within genetically modified pigs.

Which of these is a human embryo?

From Ernst Haekel’s 1874 study of vertebrate embryo development.

For some time, researchers have been studying the effect of injecting human stem cells into developing pig embryos. The result is usually that human type cells can be found in a range of locations, however, they always fail to compete effectively with the native pig cells. Researchers in the US are hoping to use genetically modified pigs that lack the coding for certain organs to allow specific “human” organs to develop unimpeded.

In all cases so far, the pig foetuses are aborted and examined before birth to determine the nature of the organs. Particular attention is given to the brains – as a major concern is the potential risk of producing pigs that think in a somehow more “human” way.

One potential benefit is that the “human” organs created this way would be an exact genetic match to the donor of the stem cells – with the possibility of rejection-free transplants.

However, at best the technique would be expensive and probably only useful for the organs that are particularly hard to transplant from conventional donors. The pancreas is a good case in point as it contains enzymes that cause it to break down quickly outside the host.

In most cases, encouraging the greater donation of organs – for example by presuming consent instead of the opposite – is likely to have a greater impact on transplantation.

Whether this technology becomes mainstream or not may depend as much on the science as the ethical objection to the very idea of blurring the boundaries between human and animal.

For those who can’t stand the tension the embryos in the image above are – a = pig, b = cow, c = rat and d = human.