When diabetes sufferer Michael Helyer had pig cells transplanted into his abdomen in 1996, experts expected they would survive for only a year or two.
Nine years later, however, medical tests have proved that thousands of the original 1 million insulin-producing "islet" cells are still in his belly. And they can still produce insulin, the essential hormone that people with type 1 diabetes cannot produce themselves.
Professor Bob Elliott, a pioneer of the experimental treatment for type 1 diabetes involving specially encapsulated cells, said he did not initially believe 49-year-old Mr Helyer when he told of still benefiting from the transplant. "I told him he was away with the fairies."
"The common wisdom was that these things can only last a year or two at the most ... But there's no doubt he's got live pig cells in him that are making insulin, albeit in small amounts," said the controversial researcher, aged 71.
Mr Helyer told the Herald this week he was able to reduce his insulin use by about one-third for over a year after the transplant. He still used slightly less than before the transplant and the pig cells were still helping, a little - "but anything is better than nothing".
His blood-glucose level is under better control than before the transplant, but he is concerned about having the beginnings of diabetic eye problems.
About 11,000 New Zealanders have type 1 diabetes, a condition with no known cause in which the pancreas stops making insulin, forcing sufferers to inject supplies. Insulin promotes glucose absorption; many diabetics have unstable blood-glucose levels. A low level can cause coma and elevated levels can gradually lead to complications like blindness and kidney failure.
At Mr Helyer's insistence, a surgeon looked inside his abdomen through a laparoscopic viewing tube and removed some of the pig cells, which when stimulated with glucose, produced insulin.
Professor Elliott said the findings were important as they showed the technique of coating the cells to protect them from rejection by the human immune system could work long-term.
Living Cell Technologies, the research company of which he is medical director, has enhanced the protection of the cells and hopes to start a human trial this year in the United States.
In New Zealand, transplants of animal material into humans remain heavily restricted under a law which was due to expire in June. The Government on Tuesday introduced a bill that would extend it to the end of next year and possibly further.
Pig cell transplants
* Used experimentally to treat type 1 diabetes.
* The insulin-producing cells are obtained from the pancreas of aborted full-term piglets.
* The cells are encapsulated in a seaweed-based gel to protect them from rejection by the human immune system.
* They are transplanted into the human abdomen, usually by an injection.
* A trial was halted in New Zealand because of fears of pig viruses spreading among humans.
* Another was run in Mexico.