Four more people with diabetes will soon be implanted with high doses of living pig cells coated in seaweed, bringing the prospect of widespread animal-to-human transplants a step closer.
Several people in New Zealand and Russia with type 1 diabetes have already received the 鈥減ig sushi鈥�, known as Diabecell, and now New Zealand company has received approval from the country鈥檚 health authorities to begin phase聽II human trials on the implants.
Type 1 diabetes occurs when insulin-producing cells in the pancreas called islets are destroyed. People with the disease must have daily insulin injections to normalise their blood glucose levels.
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But this causes blood glucose levels to yo-yo, which can lead to cardiovascular and nervous system complications, shortening the lifespan of sufferers by a third, according to Bob Elliott, LCT鈥檚 medical director.
Seaweed diffusion
LCT鈥檚 treatment uses islet cells taken from pigs to replace the cells missing from a person with diabetes. The pig islets are surgically implanted into a patient鈥檚 abdomen, from where they secrete insulin throughout the body.
To avoid immune rejection, the pig cells are coated in alginate, a substance found in seaweed that prevents immune-system cells from touching 鈥� and so recognising and attacking 鈥� the alien islets. 鈥淪o immunosuppressant drugs aren鈥檛 needed after implantation,鈥� says Elliott. However, the alginate allows nutrients and glucose to diffuse into the islets, and insulin to diffuse out, so the cells can do their job.
In the earlier phase I trials, four people with type聽1 diabetes who suffered from 鈥渉ypoglycaemic unawareness鈥� 鈥� in other words, they didn鈥檛 notice when their blood sugar levels became dangerously low 鈥� were implanted with a few of the cells. 鈥淚n one patient, the implants reduced their daily insulin dose by 25聽per cent, and hypoglycaemic unawareness disappeared,鈥� says Elliott. The other three are being monitored, and Elliott says 鈥渞esults look very satisfying鈥�.
Research is further ahead in Russia, where LCT began trials of Diabecell in 2007. Five patients have since been given higher doses and are successfully responding.
Cold pigs
According to Elliott, there are not enough human islet cells available to treat the 20聽to 30聽million people who suffer from diabetes type聽1 worldwide, so porcine islets are the best alternative.
To minimise the risk of transmitting porcine diseases into humans, LCT uses cells from pigs of Auckland Island in the Southern Ocean south of New Zealand. 鈥淭hey have lived in isolation for 200 years and are remarkably free of any form of organism that can infect humans,鈥� says Elliott.
LCT鈥檚 trial is the most promising research in the area, says from St Vincent鈥檚 University Hospital in Melbourne, Australia, who also researches pig islets for diabetes treatment, but was not involved in this work. But, he says, the results 鈥渁re quite preliminary, and demonstration of longer-term function of the islet implants will be critical鈥�, he says.
LCT implanted similar capsules in a patient in 1996: although those pig cells are still alive, few continue to produce insulin.
