What to Expect From an Islet Cell Transplant

A Step Toward a Cure for Type 1 Diabetes?

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Pancreatic islet cell transplantation is an experimental procedure for treating type 1 diabetes. The goal of this procedure is to make it possible for people with this autoimmune disease (not to be confused with type 2 diabetes) to stop taking insulin—a vital hormone produced by the pancreas that controls the levels of glucose (sugar) in blood. People with type 1 diabetes aren't able to generate insulin on their own, putting them at risk for serious and potentially fatal complications ranging from damage to nerves (neuropathy) or eyes (retinopathy) to heart disease.

Because islet cell transplantation—sometimes called allotransplantation or beta-cell transplantation—is still being studied, it is performed in the United States only in clinical trials sanctioned by the U.S. Food and Drug Administration (FDA). According to the Collaborative Islet Transplantation Registry , 1,089 people throughout the world have received islet transplants for treating diabetes,

Reasons for an Islet Cell Transplant

Pancreatic islets, also called islets of Langerhans, are one of several types of groups of cells in the pancreas—the organ that helps the body break down and use food. Among these are the beta cells, or β-cells, that produce insulin.

Insulin is vital to life. Without it, glucose quickly builds up in the blood to potentially fatal levels while the cells in the body do not receive the energy they need to function properly.

In type 1 diabetes, the immune system destroys the beta cells. It isn't known why this happens, but without functioning β-cells the body isn't able to produce its own insulin. So for people with type 1 diabetes, daily injections of supplemental insulin, or the use of an insulin pump, are the cornerstone of treatment.

Giving oneself shots or having to maintain a medical device can be a challenge, however, hence islet cell transplantation is an appealing alternative for some people.

Candidates for islet cell transplantation include people ages 18-65 with type 1 diabetes who have blood glucose levels that are difficult to manage, episodes of severe hypoglycemia and hypoglycemia unawareness—a dangerous condition in which a person can’t feel or recognize the symptoms of hypoglycemia.

Doctors consider people for islet transplantation if the possible benefits, such as being better able to reach blood glucose targets without problems outweigh the risks, including the possible side effects of immunosuppressants, medicines that recipients must take to prevent their immune system from attacking and destroying the transplanted islets.

People with type 1 diabetes who are planning to have, or have had, a kidney transplant to treat kidney failure may also be candidates for islet transplantation, which can be performed at the same time as or after a kidney transplant.

A different type of islet transplantation, called islet autotransplantation, is used for people who must have their entire pancreas removed to treat severe and chronic pancreatitis. In this procedure, the patient's own islet cells are removed from the pancreas and infused into the liver. Islet autotransplantation is not considered experimental, and people with type 1 diabetes are not candidates for this procedure.

Donor Recipient Selection Process

A major obstacle to the widespread use of pancreatic islet cell transplantation is a shortage of islet cells from donors. Only a small number of donor pancreases are available for islet transplantation each year. According to the Organ Procurement and Transplantation Network, 1,315 pancreases were recovered from deceased donors in 2017. Many donated pancreases are not suitable for islet isolation. Also, some donor islets may be damaged or destroyed during the transplant process.

To compensate for this shortage, researchers are studying ways to transplant islets from pigs or create new human islets from stem cells.

Types of Donors

Islet cells are retrieved from the pancreas of a deceased person who chose to donate their organs.

During the Procedure

Islet transplantation involves taking beta cells from a deceased donor, purifying and processing them, and then transferring them. Transplant patients typically receive two infusions containing an average of 400,000 to 500,000 islets per infusion.

The procedure usually is performed by a radiologist (a doctor who specializes in medical imaging). Using X-rays and ultrasound imaging for guidance, they will thread a catheter (a thin plastic tube) through a small incision in the upper stomach into the portal vein—a major vein that supplies blood to the liver.

Once the catheter is in position, the prepared islet cells are slowly pushed through it. Allotransplantation can be done using local anesthesia and a sedative. General anesthesia, which is riskier, is rarely necessary.

The transplant process itself is a relatively simple, non-surgical outpatient procedure that takes about an hour.

In islet auto-transplantation, doctors first remove the patient’s pancreas, then extract the islets from the pancreas and transplant them into the patient’s liver. The goal is to give the body enough healthy islets to make insulin. Patients don’t need to take immunosuppressants after islet auto-transplantation because they receive islets from their own body.

Complications

The transplant procedure can increase the risk of bleeding and blood clots. There is also a chance that the transplanted cells may not work well or at all. In addition, all of the cells may not work right away and may take time to start functioning properly. Therefore, recipients may need to take insulin until the cells begin working properly.

After Surgery

During the two weeks following surgery, new blood vessels form and connect the islets with the blood vessels of the recipient and begin to make and release insulin, with two key benefits:

  • Normalization of glucose levels without dependence on insulin injections, or at least a reduction in the amount of insulin needed
  • Reversal of hypoglycemia unawareness—a loss of the ability to sense symptoms of dangerously low blood sugar (typically, 70 mg/dL or less, according to the American Diabetes Association), such as sweating, shaking, increased heartbeat, anxiety, or hunger, and treat it accordingly

Researchers believe that ultimately a diabetes patient will need between 350 million to 750 million islet cells to be able to discontinue insulin altogether, so most islet cell recipients will need multiple transplants.


In order to receive pancreatic islets from another person, a recipient will need to be on immunosuppressive medications to prevent rejection of the cells. Some of these, such as corticosteroids, can complicate diabetes by increasing insulin resistance over time and causing a rise in blood sugars. Other types of immunosuppressants may reduce the ability of beta cells to release insulin. Additionally, immunosuppressants inhibit the immune system's ability to fight infection.

At the same time, there also is a risk that despite being suppressed by medication, the autoimmune response that initially destroyed a person's native cells to cause type 1 diabetes in the first place might be triggered again, this time attacking and destroying the newly transplanted donor cells.

Prognosis

A phase 3 clinical trial conducted by the National Institutes of Health Clinical Islet Transplantation Consortium found that a year after islet cell transplantation, nine out of 10 recipients had an A1C level (a measure of average blood glucose levels over two or three months) below 7 %, had no episodes of severe hypoglycemia, and did not need to take insulin. Two years after transplantation, seven out of 10 recipients had an A1C level of less than 7 % and did not have episodes of severe hypoglycemia, and about four out of 10 did not need insulin. The transplant recipients also had improvements in quality of life and overall health—including those who still needed to take insulin.

A Word From Verywell

Research on islet cell transplantation is currently focused on being able to collect enough islet cells by using cells from other sources, including fetal tissue and animals; Scientists are also attempting to grow human islet cells in the laboratory. Furthermore, while advances have been made in developing new and better anti-rejection drugs, more work needs to be done in this area.

Clearly, it will be some time before islet cell transplantation becomes a routine treatment for type 1 diabetes. But the concept is intriguing and worth knowing about if you or a loved one has this form of the disease. Information on joining a clinical trial on islet transplantation can be found at ClinicalTrials.gov.

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