Islet Cell Transplantation for the Treatment of Diabetes

In islet cell transplantation, insulin-producing beta cells are taken from a donor's pancreas and transferred into a person with diabetes. Once transplanted, the donor islets begin to make and release insulin, actively regulating the level of sugar in the blood.

A successful islet cell transplant can significantly improve the quality of life for a person with diabetes.

Once transplanted, the islet cells automatically monitor sugar in the body and can regulate insulin levels by delivering the appropriate amounts needed to normalize blood sugar levels, even as the body's needs change (for example, after exercising or eating).

Successful islet cell transplantation can provide the following benefits:

• It can eliminate the need for frequent blood sugar measurements and the need for daily insulin injections. Although only a few people are completely free of insulin injections a year after transplantation.
• It can provide more flexibility with meal planning.
• It can help protect against the serious long-term complications of diabetes, including heart disease, kidney disease, stroke, and nerve and eye damage.

As with any organ or tissue transplant, rejection of the donor cells is the greatest challenge in those with diabetes. The immune system serves to protect the body from "invading" substances that do not belong -- bacteria and viruses, for example. Even when needed donor tissue is transplanted, the recipient's immune system recognizes it as "foreign" and tries to destroy it. This attack on the donor tissue is called "rejection."

All transplant recipients must take, for the rest of their life, strong drugs to suppress the immune response and prevent rejection. Many of these drugs have serious side effects. The long-term effects of these immunosuppressive or anti-rejection drugs are not yet known, but it is suspected that they may increase the risk of cancer.

Scientists developed the procedure for transplanting islet cells to treat diabetes in the 1960's. The first transplantation attempts, which began in the 1990's, succeeded only 8% of the time, which was attributed to the fact that anti-rejection drugs available at the time interfered with insulin's effectiveness.

But in 1999, a clinical trial conducted at the University of Alberta in Edmonton, Canada, brought new hope. Using enhanced techniques to collect and prepare the extremely fragile donor islet cells, as well as using improved anti-rejection drugs, the researchers achieved a 100% success rate. All of the patients in their trial were freed from the need for insulin for at least one month. The process followed by the researchers -- dubbed the "Edmonton Protocol" -- is still being studied in clinical trials around the world.

Typically, candidates for islet cell transplantation are between the ages of 18 and 65, have had type 1 diabetes for more than 5 years, and are experiencing diabetes-related complications such as frequent periods of unconsciousness due to lack of insulin and early signs of kidney problems that could lead to kidney failure.

Because it is still considered an experimental therapy, islet cell transplantation for diabetes is not widely available. There are currently 17 U.S. centers participating in islet cell research programs. The American Diabetes Association recommends that pancreas or islet cell transplantation be performed only in these major centers, which are best equipped to handle the complex and long-term medical and personal needs of transplant patients.

There are two main areas of focus in islet cell transplantation research:

1. Collecting enough islet cells to do the transplant: Obtaining enough islet cells for transplantation is a major challenge. Typically, about 1 million islet cells are needed, which is equivalent to two donor pancreases. Because the need surpasses the number of human donors available, researchers are studying the use of cells from other sources, including fetal tissue and animals such as pigs. Researchers are also attempting to grow human islet cells in the laboratory.
2. Preventing rejection: Researchers continuously seek to develop new and better anti-rejection drugs. Many advances have been made in anti-rejection drugs over the past 15 years. Newer drugs -- such as tacrolimus (FK506) and rapamycin -- have fewer and less harmful side effects than some older drugs like cyclosporine and prednisone.

Researchers are also working to develop methods of transplanting islet cells that will reduce or eliminate the risk of rejection and the need for immunosuppression. One approach involves coating the islet cells with a special gel that prevents the immune system from recognizing and targeting the donor cells.

WebMD Medical Reference