Transplanting animal organs into humans, once the great hope for ending the problem of organ shortages, may prove too difficult and risky to develop, according to a new report. Some scientists believe stem cell research may provide a better solution.
The report, from the United Kingdom Xenotransplantation Interim Regulatory Authority (UKXIRA), says 鈥渢he likelihood of whole-organ xenotransplantation being available within a clinically worthwhile time frame may be starting to recede.鈥� The prospect of using animals like pigs for spare parts, they say, 鈥渁ppears still to be some way off鈥�.
鈥淚t鈥檚 no nearer than when we started three or four years ago鈥� says John Dark, professor of cardio-thoracic surgery at the University of Newcastle and a member of the UKXIRA committee.
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Richard Foreshaw, spokesman for the UKXIRA adds: 鈥淲e鈥檙e not ruling out whole organ transplants. But the way things are looking at the moment, it really is slowing down. The other therapies are making more progress, but it鈥檚 worth looking at all the options at once.鈥� More than 6700 people in the UK were waiting for an organ transplant operation at the end of 1999, and 5500 at the end of 2000.
Pig viruses
Whole-organ xenotransplantation has been consistently difficult for researchers. Rejection of such organs by the immune system is a major problem. And the report points out that animal studies have not even proven that animal organs are capable of sustaining life in humans.
鈥淢y guess is we鈥檝e got a 50-50 chance of getting xenotransplantation working,鈥� says Andrew George, a xenotransplantation researcher from the Imperial College School of Medicine, London.
But no one knows how safe xenotransplantation is. Research has shown that transplanted cells can transmit inherited viruses [New 杏吧原创, 26 Aug 00, p 7], allowing harmless junk DNA from one species to become dangerous in another. But other research indicates that human recipients of pig cells have stayed healthy, often for years [New 杏吧原创, 8 Aug 98, p 4]. The report concludes that it is 鈥減rudent to assume that all forms of xenotransplantation carry a risk of some degree.鈥�
鈥淭here鈥檚 never been any assurance on the safety of xenotransplantation. There鈥檚 always been a huge risk,鈥� says Foreshaw.
Growing organs
Stem cell research targeting disease was made legal in the UK in January and the report says it might prove a better option because it has no risk of cross-species infection.
But stem cell research is still in its infancy and until it catches up, the report says, the use of pig cells instead of human stem cells could offer hope to sufferers of Parkinson鈥檚 and Huntington鈥檚 disease, epilepsy and strokes.
Growing whole organs from human stem cells is still far in the future 鈥� though, for example, bladders have been grown for dogs. Most researchers say it is best to continue studying both options for now, along with mechanical replacements for organs.
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