A news item published recently describes a scientific experiment which may permit human organs to be cultivated in live animals in the coming years. This technique could facilitate access to organs for transplants and address the current shortage in transplantable organs.

In the study described above, (PNAS, 110; 4557-4562, 2013), scientists from the University of Tokyo genetically modified a white-coat pig to inhibit pancreas formation in its body. An embryo was produced from this animal which lacked a pancreas. Stem cells were removed from this embryo and then transplanted into another pig; this time in a pig of the black-coat variety. These were subsequently transplanted into white pig embryos which lacked pancreas. These embryos were implanted in the uterus of a third pig, resulting in the production of white-coat pig foetuses which would have otherwise been unable to develop a pancreas on their own but which were born with a pancreas arising from the stem cells from the black-coat pigs. In other words, this technique was able to develop a pancreas in pigs in which the development of this organ had been inhibited.

The authors of this paper believe that this type of technique could be used with human iPS cells, which could be injected into pig embryos lacking a pancreas. The transplanted cells would then produce a pancreas in the embryo whose ability to generate a pancreas had been inhibited; a procedure which would produce a near-human pancreas that could later be transplanted in patients requiring a pancreas.

In medical terms, this technique undoubtedly represents a leap forward, yet it brings up objective ethical issues. A technique such as this cannot ensure that human cells transplanted into pig embryos lacking in pancreases will remain in the pancreatic area – they may travel to other areas of the body, which would result in a pig-human hybrid animal – a result that would be very hard to accept in ethical terms.