Endocrine pancreas

Islets of Langerhans is the area in which the endocrine (i.e., hormone-producing) cells of the pancreas are grouped. Discovered in 1869 by the famous German pathological anatomist Paul Langerhans, the islets of Langerhans constitute approximately 1 to 2% of the mass of the pancreas. There are about one million islets in a healthy adult human pancreas, which are distributed evenly throughout the organ; their combined mass is 1 to 1.5 grams.

Cell types

Hormones produced in the Islets of Langerhans are secreted directly into the blood flow by five different types of cells:

• Alpha cells producing glucagon (15-20% of total islet cells)
• Beta cells producing insulin and amylin (65-80%)
• Delta cells producing somatostatin (3-10%)
• PP cells producing pancreatic polypeptide (3-5%)
• Epsilon cells producing ghrelin. (<1%)

Islets can influence each other through paracrine and autocrine communication, and beta-cells are coupled electrically to beta cells (but not to other cell types).

Paracrine feedback

The paracrine feedback system of the islets of Langerhans has the following structure:

• Insulin: Activates beta cells and inhibits alpha cells.
• Glucagon: Activates alpha which activates beta cells and delta cells.
• Somatostatin: Inhibits alpha cells and beta cells

Electrical activity

Electrical activity of pancreatic islets has been studied using patch clamp techniques, and it has turned out that the behavior of cells in intact islets differs significantly from the behavior of dispersed cells.

As a treatment for type I diabetes

Because the beta cells in the islets of Langerhans are destroyed in type I diabetes, clinicians and researchers are actively pursuing islet transplantation technology as a means of curing this disease. Rachel Harris, islet cell recipient, was transplanted at the Diabetes Research Institute in Miami, Florida. Rachel became the world's longest surviving insulin-free diabetic according to the Miami Herald.

Islet transplantation currently requires potent immunosuppression to prevent host rejection of donor islets. An alternative source of beta cells, such an islets derived from adult stem cells or progenitor cells of a diabetic would eliminate the need for immuosuppressive therapy, and be safer for diabetics.

Transplantation

With the possibility of restoring beta cells, the Chicago Project headed at University of Illinois at Chicago Medical Center is investigating ways to regenerate beta cells in vivo. With that being said, beta cells experience apoptosis early and thus are destroyed within a normal-functioning pancreas. The source of this seems to come from the transfer of Pander, a gene that works by attaching to RNA. Pander, when active, causes the beta cells to be blocked at S phase, which induces apoptosis. This loss of beta cell mass eventually leads to a loss of most of the transplanted beta cells.