HITS | Frequently Asked Questions

Frequently Asked Questions

Here are some of the more frequent questions about islet transplantation. For more detailed background information, contact Rich Murphy, Director of Community Relations at PNRI, (206) 726-1200, rmurphy@pnri.org.

What are islets?

Islets ("eye-lets") are groups of cells. Their mid-19th century discoverer, Paul Langerhans, called them islets because they look like small islands in a sea of other tissue. In the healthy pancreas, islets contain four types of cells essential to metabolism and the management of glucose levels in the blood. Though a normal adult pancreas contains approximately a million islets, they account for only 2-3% of the pancreas's tissue.

Why are islets important to diabetes?

Beta cells-one of the four types of cells in pancreatic islets-produce the insulin needed for proper metabolism. In type 1 diabetes, beta cells are completely destroyed and thus unable to produce any insulin. In type 2 diabetes, they produce insulin erratically or deliver it ineffectively to the body. Properly functioning beta cells are able to return diabetic patients to normal insulin secretion and blood sugar control.

What is islet transplantation?

Healthy islets are removed from a donor pancreas, purified, and then inserted by catheter into the liver of a diabetic patient. The collection and purification of the islets is technically complex, but the transplantation itself is relatively simple. It can be performed while the patient is fully conscious and may take less than an hour to complete. Following the transplant, patients take immunosuppressive drugs to keep their body from rejecting the new islets.

How is islet transplantation different from pancreas transplantation?

Pancreases have been transplanted successfully for many years as a treatment for patients with advanced diabetes. But pancreas transplantation is major surgery, undertaken usually only when the diabetes complications are so severe as to warrant the trauma and risk of the surgery. Islet transplantation is far simpler and faster. It can be performed on diabetes patients with far less risk and before the worst complications of the disease are able to develop. Or alternatively, on patients for whom glucose control is very difficult but for whom a whole pancreas transplant is deemed too risky.

Why are islets transplanted to the liver instead of to the pancreas?

The pancreas is anatomically more difficult to reach than the liver. So it is easier to infuse the islets through the portal vein of the liver than to inject them into the pancreas. The liver also provides an environment in which the islets can thrive and flourish.

Why aren't transplanted beta cells destroyed--as the recipient's own beta cells were--by the mechanisms that led to the patient's diabetes?

Type 1 diabetes is an autoimmune disease. For reasons not yet fully understood, the body's immune system kills its own beta cells. The beta cells infused by islet transplantation are not one's own, so the immune system does not respond to them in the same way. The ordinary rejection mechanism of the immune system does need to be controlled after islet transplantation, and therapy is given to block recurrence of type 1 diabetes.

How is immune rejection controlled after islet transplantation?

A key recent discovery in islet transplantation is the combination of anti-rejection drugs that will protect transplanted islets without causing major side-effects to the patient. The removal of steroids from the anti-rejection drugs appears to reduce toxicity to both the islets and the patients.

What is HITS?

HITS-Human Islet Transplantation in Seattle--is a consortium of six medical care and research facilities in the Northwest, collaborating together to advance islet transplantation as a cure for diabetes.

The consortium includes the Pacific Northwest Research Institute, Swedish Medical Center, Virginia Mason Research Center, the University of Washington Medical Center, the Puget Sound Blood Center, and the Fred Hutchinson Cancer Research Center.

Two clinical studies of islet transplantation are currently being conducted by the Seattle group-one in which islets are transplanted alone; one in which patients receive both islet and kidney transplants at the same time. Both studies draw their procedures from one established at the University of Alberta in Edmonton, Canada, and called the "Edmonton Protocol."

What is the Edmonton Protocol?

Human islet transplantation has only recently achieved promising success. In 2000, doctors in Edmonton reported that a small number of diabetes patients continued to produce their own insulin, with no appreciable side effects, after islet transplantation. Nine sites in North America, Canada, and Europe were then selected to replicate the Edmonton procedure, to test its effectiveness on more patients in different treatment centers. The coordinating center for these various sites is the Immune Tolerance Network, a program established and sponsored by the National Institutes of Health. Seattle is one of the nine test sites.

How similar are Seattle's procedures to Edmonton's?

In islet only, the procedures are identical.
In the kidney-islet procedure, the islet transplant is similar to Edmonton's, but it is conducted in conjunction with kidney transplant surgery.

How are patients chosen for a HITS transplant?

A small number of patients have been selected for the earliest HITS transplants. For islet only transplants, they are chosen by the Immune Tolerance Network from a pool of volunteer candidates. Then they are further screened by HITS to meet the stringent eligibility requirements of the research study. Participants in the kidney-islet program, are volunteers from among the kidney patients of participating HITS institutions. They too must meet strict health criteria to be included.

Among other requirements of age, weight, glucose levels, and health history, participating patients all have type 1 diabetes, all are adults, and, in spite of scrupulous diet and lifestyle control, all still experience extreme insulin failure.

Where else are experimental islet transplants being conducted?

Under the general auspices of the Immune Tolerance Network, the Edmonton protocol is being tested by the University of Alberta, six research centers in the U.S., and medical centers in Italy, Germany, and Switzerland.

Islet transplantation is also being conducted independently at a number of other institutions in the U.S. and abroad.

How effective is islet transplantation as a cure for diabetes?

Early results indicate that this is as effective as whole pancreas transplantation for the treatment of type 1 diabetes. But islet transplants from donor pancreases are sharply limited by the number of donors. Researchers are conducting promising beta cell and stem cell research that may make healthy islets widely available. With such resources, islet transplantation may become possible for millions of patients suffering from diabetes.