Islet Cell Transplant for Type 1 Diabetes

A Step Toward a Cure for Diabetes Mellitus?

lab tests
Stocksy United

Pancreatic islet cell transplantation is an experimental procedure for treating type 1 diabetes (diabetes mellitus). 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 no longer need to take insulin—a vital hormone produced by the pancreas to control 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, which sometimes is called either 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). Only 1089 people throughout the world have received islet transplants for treating diabetes, according to the Collaborative Islet Transplantation Registry (CITR).

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.

Why Pancreatic Islets Are Important

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 obviously, 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 wearing at best. Islet cell transplantation is one approach to finding an alternative to supplemental insulin.

Overview of Allotransplantation

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, he or she 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. inserted in the proper position the islet cells are slowly pushed through. Allotransplantation can be done with local anesthesia and a sedative—general anesthesia, which is riskier, isn't necessary.

Benefits

Once implanted, the beta cells in these islets 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 cells to be able to discontinue insulin altogether and so most islet cell recipients will need multiple transplants.

How Effective Is Allotransplantation?

A phase 3 clinical trial conducted by the National Institutes of Health (NIH)-sponsored 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 percent, had no episodes of severe hypoglycemia, and did not need to take insulin. Two years after transplantation, 7 out of 10 recipients had an A1C level of less than 7 percent and did not have episodes of severe hypoglycemia, and about 4 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.

Disadvantages

In order to receive pancreatic islets from another person, a recipient will need to be on immunosuppressive medications to prevent rejection of the cells. Certain of these, 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. And, obviously, 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.

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.

A major obstacle to the widespread use of pancreatic islet cell transplantation as a treatment for diabetes is a shortage of islet cells from donors—many times there are not enough healthy cells to transplant and there aren't enough donors.

Lastly, allotransplantation is expensive. Not only is the procedure itself costly, but follow-up appointments and immunosuppressant medications add to the tally.

Future Expectations

In addition to perfecting islet cell transplantation in human trials, there also is ongoing research to explore the possibility of creating human beta cells from stem cells in a lab. Scientists believe such cells would generate a larger number of more efficient islet cells. Although much more work needs to be done in the area of stem cell transplantation, it ultimately could bring us one step closer to curing diabetes. 

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