Capsules containing pig pancreas cells are implanted into the body of a patient.

Credit: Living Cell Technologies

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MELBOURNE: Cells transplanted from the pancreas of a pig are still producing insulin in a diabetic New Zealand man after an amazing 10 years – prompting clinical trials to see if the technique could have wider applications.

"It is a profound step forward for safe, effective and long-term diabetes control,” said Bob Elliot, the chief scientific advisor of Living Cell Technologies (LCT), the Canberra, Australia-based company conducting the research. “Though it's only one patient, it’s hard to dismiss.”

Diabetics are incapable of regulating their own blood sugar. They survive by daily injections of insulin, a hormone manufactured by ‘beta cells’ of the pancreas which regulate blood sugar in healthy humans. But because injections don’t mimic the precise way beta cells deliver insulin, in the long-term they can still suffer blindness and kidney failure.

Type 1 diabetes is usually caused when the body mistakenly destroys its own pancreatic cells. It has long been a dream of researchers to cure diabetes by replacing a patient’s lost beta cells with healthy ones from other sources.

Because of their physiological similarity to those of humans, pig cells have been the hot favourite. So far, though, no one has demonstrated that transplanted pig cells can stay alive and function for more than a few months. The New Zealander's experience may change all that.

LCT reports in the current issue of the journal Xenotransplantation that pig pancreas cells are still alive 10 years after being grafted into a diabetic patient named Michael Helyer, and are producing appreciable amounts of insulin.

According to Elliot, “There’s been a lot of scepticism over whether transplanted cells would work and if they did that it would only be for a short time.”

The discovery was made by chance. In 1996 six diabetic volunteers had newborn pig beta cells transplanted into the fluid-filled peritoneal cavity that houses the stomach, intestines, liver and pancreas. The hope had been that newborn pig cells would be less visible to the immune system than the cells of adults and would survive by absorbing nutrients directly from fluid in the cavity. In four of the patients all the cells disappeared, presumably destroyed by the immune system. But in two of the patients the cells were first encased in a jelly-like capsule. And in these patients, the cells survived. One of those patients was Michael Helyer.

At first Helyer’s graft reduced his need for injected insulin by 30 per cent, but after a year he was back to needing his original dose of insulin. The researchers concluded it was time to go back to the drawing board and spent the last ten years testing the cells in animals from mice to monkeys.

But Helyer never stopped insisting that he was feeling better as a result of his graft. So finally, to settle the point, the researchers checked his graft and found that indeed the round jelly-like capsules were still there, now embedded into tissue, and produced tiny amounts of pig insulin.

“This is a very encouraging finding” that warrants further research commented Jayne Foster, a scientist at the Diabetes Transplant Unit at Sydney’s Prince of Wales Hospital. Foster has tried transplanting encapsulated pig beta cells into mice but so far has not been able to get them to survive the onslaught of the immune system.

For Australia’s 140,000 type 1 diabetics, Helyer’s experience shows that pig transplants are not pie in the sky. However human trials can’t take place in Australia until at least 2009, because of a moratorium on transplanting animal organs into humans. The National Health and Medical Research Council stopped such trials because it was concerned about animal viruses slipping into the human population. AIDS, Ebola, Mad Cow disease and bird flu, for instance, crossed into the human population from animals.

However, LCT has access to remarkably pristine pigs — a herd isolated in the remote, sub-Antarctic Auckland islands since 1852, that has not had contact with modern viruses. “They are free of any known transmissible disease, which is more than you can say about donated human organs,” said Elliot.

Because of Australia’s moratorium, LCT is planning human trials in Russia next month and is waiting to hear whether New Zealand will also give it the go-ahead.

More information:

Animal-derived organ transplants, Wikipedia