What are Islets of Langerhans?
Physician Paul Langerhans first identified round structures in the pancreas as “islets” (Latin for islands) within a sea of exocrine pancreas tissue. These structures, named in his honor as “Islets of Langerhans”, contain the cells needed for regulating blood glucose levels in the body. Islets consist of several cell types, including insulin-secreting beta-cells that lower blood sugar and glucagon-secreting alpha-cells that raise blood sugar (to counteract insulin’s effects).
We study the insulin-producing beta-cells inside these islets because these cells are critical to regulating blood sugar. Importantly, problems with beta-cells are 100% of the cause of type 1 diabetes (autoimmune-mediated diabetes mellitus, sometime called “juvenile” or insulin-dependent (IDDM)) and ~50% of the cause of type 2 diabetes mellitus (obesity-associated diabetes, sometimes called “adult-onset” or “non-insulin–dependent” (NIDDM)).
Islets are tricky to study because they are widely separated from one another, and they make up only 1-2% of the total volume of the pancreas. In order to study these micro-organs in a dish, these islets must first be isolated from the rest of the pancreas, a tricky process.
Islets are obtained by an isolation process that consists of two basic steps:
A mixture of digestive enzymes called collagenase is injected into the pancreas through the common bile duct. Once the pancreas inflates with collaganease, it is removed and digested for a specified time. The pancreas is then gently broken apart in solution. Figure Panel A shows what a digested pancreas looks like in a dish. A single amber-colored islet is located in the center of the image (and a smaller one in the upper left corner.
The pancreas is gently broken apart and then suspended in a Histopaque gradient in a tube. The container is then centrifuged at high speed and the gradient captures the islets while the denser remainder of the pancreas gets sucked down into a pellet. A much more detailed description of this process is described in our "Practical Guide to Islet Isolation and Assessment"