Transplants - On The Horizon: Diabetes A Plan For Living

Content provided by the Faculty of the Harvard Medical School

Transplants

Pancreas transplantation is the only therapy that can "cure" type 1 diabetes. Although currently limited by organ supply and other factors, researchers are working on methods to make transplantation a viable option for more people.

Pancreas transplants

There's been considerable progress in whole-organ pancreas transplants. A person receiving a new pancreas, or segments of another pancreas, may have normal blood sugar and no longer need insulin. However, because of the need for major surgery and lifelong medication to suppress the immune system from attacking a foreign organ, the procedure isn't appropriate for most people with type 1 diabetes. It may be recommended for people who already have complications and are going to have a kidney transplant, because the pancreas transplant can be done at the same time and will be covered by the same immunosuppressant drugs. However, organs for transplantation are scarce.

Islet cell transplants

As an alternative to whole-organ transplants, scientists have been exploring methods for transplanting only the insulin-producing islet cells in the pancreas. In this procedure, cells are extracted from a donor pancreas and implanted in another person, usually in the liver (which has a large blood supply that can provide nutrients to the donated cells). There, the new islets begin to make and release insulin. The goal is to infuse enough islets to allow people with type 1 diabetes to forgo taking insulin daily. This therapy could also theoretically help people with type 2 diabetes, but the costs of treating the tens of millions of people with type 2 diabetes probably makes this highly unlikely, even if there were an enormous supply of islet cells, which isn't the case.

Scientists have made many advances in islet transplantation over the past 25 years. A new procedure called the Edmonton Protocol, developed at the University of Alberta in Edmonton, Canada, has been used since 1999 to treat patients with type 1 diabetes. The Edmonton Protocol differs from previous efforts because it transplants a large number of fresh islets and uses a new combination of immunosuppressant medications. Approximately 80% of patients in the study were "cured," at least in the short term — achieving normal blood sugars without need for insulin injections. The Edmonton Protocol has been tested by other centers as well with initial positive results.

Researchers use specialized enzymes to remove islets from the pancreas of a deceased donor. For an average-size person, the transplant requires about 1 million islets. To extract this many islets generally requires at least two pancreases, so the procedure involves multiple donors. Because the islets are extremely fragile, transplantation occurs soon after they're removed. The surgeon uses ultrasound to thread a small catheter into the liver. The islets are then injected into a large vein in the liver via the catheter. The entire procedure takes less than an hour. Although the early results of the Edmonton Protocol are very encouraging, more research is needed to answer questions about how long the islets will survive and how often the transplantation procedure will be successful.

One drawback is that recipients must take drugs similar to those used in whole-organ transplants to prevent their immune systems from rejecting the transplanted islets. Also, the demand for islet cells far outstrips the supply of pancreases. An alternative source of cells needs to be found before transplantation can become a practical option for the majority of people with type 1 diabetes.

Last updated:	January 23, 2007