Islet cells are sugar-sensing cells in the pancreas that release insulin in order to maintain normal blood sugar levels in the body. In type 1 diabetes, the cells can no longer make insulin because the body's immune system has destroyed them. Type 1 diabetics must take daily insulin injections, usually a complex combination of short and long acting insulin.

Islet cell transplantation involves removing insulin-producing cells from a donor pancreas and transferring them into a person with diabetes. It's a non-surgical procedure in which the donated cells are inserted through a needle directly into the liver. Scientists developed the procedure in the 1960s, but the first islet transplantation attempts didn't take place until the 1990's. To everyone's disappointment, only 8% of the first transplants were successful. The problem was the same faced in other organ or tissue transplants – the recipient's immune system recognized the islets as foreign invaders, and attacked them. Adding to the problem, the anti-rejection drugs in use at the time interfered with insulin's effectiveness.

Canadian researchers at the University of Alberta (U of A) made a major breakthrough in 1999. Using sophisticated islet collection and preparation techniques and improved anti-rejection drugs, they achieved an impressive initial 100% success rate for the first month. But most of their patients eventually had to return to insulin injections as the transplanted islets lost their ability to function, although taking lower doses.

Over ten years later, islet transplantation is still an experimental procedure. Rejection issues remain, and it's difficult to obtain the typically 1 million islet cells needed for one procedure – the equivalent of two pancreases. Islet transplants are currently being performed at 17 research centers across the US, but are not widely available. The procedure is normally restricted to type 1 diabetics between the ages of 18 and 65 who have had diabetes for more than 5 years and have trouble controlling their blood sugar, resulting in serious complications.

In a successful islet cell transplant, the donor islets make insulin and release it into the patient's bloodstream. They also monitor and stabilize blood sugar levels, eliminating the need for daily insulin injections and frequent blood sugar monitoring. But islet transplant patients must take strong anti-rejection drugs for the rest of their lives, many of which have serious side effects. Unfortunately, most patients need more than one transplant to produce enough insulin that they can stop taking insulin injections. Although islet transplants still fall short of a cure, a successful procedure improves the quality of life of the patient, and lowers the risk of serious long-term diabetes complications such as stroke, heart disease, kidney disease, and eye and nerve damage.

Progress continues to be made towards better anti-rejection drugs, and improved methods to transplant the cells. Researchers are also attempting to obtain donor islets from other sources such as animals, and even trying to grow islet cells in the laboratory. The University of Wisconsin Health Centre claims about 80% of patients receiving an islet transplant have been able to stop taking insulin completely, and that those that still need insulin injections achieved better glucose control. As the procedure is still so new, the longest known period of insulin independence following a US transplant is 4 years. The pioneering U of A program reports that 15-20% of their patients remain insulin independent for 5 years after treatment, and these results are improving.

In the meantime, most Type 1 diabetics will continue to control their condition with diet, exercise, lifestyle changes and a combination of short and long acting insulin, and to follow the developments in islet transplants with great interest.