Pig parts offer hope for diabetics

By STEVE CONNOR

Medical researchers have successfully treated diabetes in laboratory monkeys by transplanting pancreatic tissue from pigs - giving hope that pig transplants may one day be used to cure childhood diabetes in humans.

The American research on monkeys follows a controversial human trial last year involving New Zealand scientist Professor Bob Elliott, which transplanted insulin-producing pig cells into a diabetic teenage boy.

The US scientists say the monkeys have survived for more than two months without the regular injections of insulin that they previously needed.

Tissue rejection - which is far more violent in transplants between species - was controlled by a sophisticated cocktail of drugs, which stopped the monkeys' immune systems from attacking the alien tissue.

Professor Bernhard Hering, who led the study at the University of Minnesota , said that the pig's islets of Langerhans - the insulin-producing cells of the pancreas - carried on making insulin for more than 70 days.

"This is very significant because, while we have been able to reverse diabetes in past islet studies, we had only seen two-to-three week survival times before the graft was lost due to the overwhelming rejection response," Professor Hering said.

Eleanor Kennedy, research manager for the charity Diabetes UK, said that the study was a "solid advance" which took the field forward.

"Anything that overcomes the need for human islets is a big advance," Dr Kennedy said.

Childhood or Type-1 diabetes affects some 400,000 people in Britain alone and typically is caused by the pancreas' inability to produce enough insulin, the vital hormone controlling glucose sugar levels in the blood.

Regular injections of insulin can control the disorder but apart from the inconvenience and pain of using needles, there is always a risk of using too much or too little of the hormone.

However, a small number of diabetics - about 1 per cent - overreact to the smallest change in levels of glucose in the blood and for these patients insulin injections do not work well. They would probably be the first candidates for pig-to-human transplants.

In recent years scientists have proposed that pigs could be genetically engineered to produce organs and tissues that are more compatible with the human immune system and pancreatic transplants are a prime candidate for such research.

Professor Hering's research was sponsored by a Immerge BioTherapeutics, a company investigating ways of making xenotransplantation - the transfer of organs and tissues from animals to humans - safe and effective

Experiments on genetically modified pigs have already demonstrated that it is possible to produce porcine tissue and organs that in principle are well tolerated by other animals, such as primates, said Julia Greenstein, president of BioTherapeutics.

"We are looking at both islet and solid organs for potential xenotransplantation from the strain of miniature swine we are developing and are currently engaged in pre-clinical trials in both areas," Dr Greenstein said.

"In this swine, we have been able to knock out the gene that is responsible for beginning the immediate and overwhelming rejection process that happens in transplants between species."

But In Britain, the proposals to carry out the first xenotransplants on humans have ground to a halt because of fears that a pig virus - porcine endogenous retrovirus - may inadvertently be transferred to humans.

The same has occurred in New Zealand. Last year Auckland company Diatranz announced a breakthrough in a trial in Mexico, where a teenager with diabetes was able to stop insulin injections after receiving transplanted insulin-producing pig cells.

But plans for tests in the Cook Islands were abandoned after the New Zealand Government intervened.

The Government also banned transplants of animal cells into people, except by special ministerial approval, because of the risk of animal viruses passing to humans.

Professor Bob Elliott, founder of Diatranz, responded by seeking approval for trials in Australia.


Herald Feature: Health

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