Cell implant injected into the eye could help to control Type 1 diabetes
TYPE 1 diabetes could be tackled by a new technique that involves implanting insulin-producing cells into the eye.
This has been found to cut the need for regular daily insulin shots by more than half in animals, and is now to be tested in humans.
While type 2 diabetes is linked with lifestyle and occurs when the body makes insufficient insulin – the hormone that mops up sugar in the bloodstream – type 1 is caused by the immune system destroying insulin-producing cells in the pancreas known as islet cells. There’s no cure and patients require multiple doses of insulin by injection or pump every day.
Some patients are offered a transplant of insulin-producing cells into the liver, which can potentially cut the need for insulin altogether. However, even with anti-rejection drugs, the cells come under attack, and one trial at the University of British Columbia in Vancouver reported that half the cells were lost within days. The immune-suppressing drugs needed to limit such attacks can also cause side-effects, such as an increased risk of infections and cancer.
In a new trial, patients will have donor cells injected into the anterior chamber – the fluid-filled space between the iris (the coloured part of the eye) and the inner surface of the cornea at the front. This area has been chosen as it has ‘immune privilege’, meaning it does not launch an immune attack on foreign bodies, so the hope is that the transplanted cells won’t be targeted.
The eye is one of the only areas in the body with immune privilege and it’s thought this protects vision from the damage that may occur with swelling and inflammation that accompanies an immune response.
In the trial at the Bascom Palmer Eye Institute in the US, 10 patients with type 1 diabetes who are blind in one eye will have islet cells donated from cadavers infused into their eye through a tiny incision in the cornea. The procedure, done under anaesthetic, takes about 25 minutes.
Patients will be monitored for six months to check how the treatment affects their insulin needs and whether symptoms and blood sugar levels have improved.
(The participants are all on anti-rejection medication having also had kidney transplants – but researchers hope to ultimately demonstrate the need for little or none of these drugs.)
Several animal studies have shown the procedure can be highly effective. When doctors at the Bascom Institute and Miami University transplanted cells into the anterior chamber of the eye of a baboon with diabetes, the animal’s own insulin production increased after three months, while the need for external insulin dropped by 60 per cent. Its eyesight was unaffected.
Commenting on the research, Dr Ali Aldibbiat, a consultant in diabetes and endocrinology at the Dasman Diabetes Institute in Kuwait and honorary research associate at Newcastle University, says islet transplantation has been increasingly used over the past two decades. He adds: "We eagerly wait for the result of the trial to see if this transplantation approach is safe for the eye and whether the transplanted islets are effective in treating diabetes."
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