Bioencapsulation & Porcine Islet Xenotransplantation

The Islets of Langerhans are clusters of hormone-secreting endocrine cells found scattered within the pancreas which play a seminal role in regulating macronutrient metabolism. In Type 1 Diabetes, a condition that affects over 3 million Americans, the body’s immune system attacks and gradually destroys the cells within these islets that secrete the hormone insulin. Since insulin is a hormone that is indispensable in carbohydrate, protein and fat metabolism, without it, most organs in the body rapidly lose their ability to utilize and store energy derived from glucose. This results in elevated levels of glucose  in the blood, termed hyperglycemia, and a loss of glucose in the urine, termed glycosuria. Untreated, type 1 diabetics develop many of the debilitating complications of chronic hyperglycemia and glycosuria such as severe weight loss, ketoacidosis, retinopathy, neuropathy and nephropathy. Unfortunately, insulin administration through the use of insulin pumps or syringes several times a day remains the current standard of care. In addition to being burdensome on the individual, this treatment modality is fraught with possibly fatal complications secondary to hypoglycemia often seen due to incorrect or over-zealous insulin dosing. Such episodes of hypoglycemia may even lead to loss of consciousness, coma or death.

Although human islet allotransplantation, i.e. the transplantation of islets isolated from the pancreas of a deceased donor, has proven to reverse hyperglycemia in type 1 diabetes, fewer than 3000 donors are available annually for this procedure which also entails the administration of dangerous immunosuppressive therapy in order to prevent transplant rejection.

Encapsulation within biocompatible polymers has demonstrated great success in reversing hyperglycemia in several small and large animal studies. The  benefits of encapsulation are manifold, but their greatest advantage lies in their ability to afford protection from the immune system while remaining selectively permeable to nutrients and islet-secreted hormones.

Several bioencapsulation devices are currently being studied for use in islet transplantation. An exhaustive review of current advances in this rapidly evolving field can be found here.