If the trials are successful, the use of pigs' organs as replacements for faulty human ones could be widespread within five years, says Christopher Sandler, chief executive of Imutran. John Wallwork, director of transplantation at Papworth Hospital in Cambridgeshire, said: "It could remove the lottery for life that currently faces patients on the transplant list. At the moment the paradox is that we are waiting for healthy people to die so that the sick can live."
Globally, there is a huge shortfall between the number of organ donors and those awaiting transplants. Waiting lists are typically months long, and in the UK an average of 80 people die every day waiting for a suitable organ.
Imutran has already succeeded in transplanting genetically engineered pigs' hearts into monkeys, which have then survived for more than 60 days. Normally if an organ is transplanted between species - known as "xenotransplantation" - the animal dies within a few hours because the immune system tears the new organ apart. A US firm using a different method only managed to keep the animals alive for 30 hours.
The key to Imutran's technique is to overcome the body's natural tendency to attack and destroy any foreign body or tissue inside it. This is done by inserting a tiny fragment of DNA - the body's genetic blueprint - from a human cell into a pig embryo. The human DNA is incorporated into the pig's own DNA.
Although outwardly the pig looks normal, the surface of all of its cells contains an extra protein, from the human DNA. If a cell from that pig were put in a human, the extra protein should fool the body's defence mechanism into treating the cell like one of its own. Pigs were chosen because their organic make-up is surprisingly similar to that of humans.
Mr Wallwork says that no patient would be given a pig organ without their informed consent. Dr David White, director of research for Imutran, says that the moral question of using animals purely for organ donation has already been dealt with. "We have been using insulin from pigs to treat humans for generations. We have been using heart valves from pigs for years. I don't think a moral question can be tissue-specific. You can't accept a pig's heart valve but not the heart." Mr Sadler adds, "If it were you, how would you feel about the choice between staying on the waiting list or helping science?"
However, the Government has announced that it is setting up an ethics committee to examine the issue. It will be chaired by Ian Kennedy, who is professor of medical law and ethics at King's College, London. One of Imutran's biggest worries is the possibility of the transfer of viruses or disease from pigs to humans. "We have pulled together a large group of experts in pig disease to check on this. We will make sure that the pigs are free of pathogens and won't transmit disease to patients," said Dr White.
The British Heart Foundation said the results seemed "another encouraging step", while the National Kidney Foundation said it viewed the news with "cautious enthusiasm". Michael Thick, transplant consultant at the Freeman Hospital in Newcastle upon Tyne, said: "The transplant community is waiting with bated breath for the results of the clinical trials."Reuse content