Increased Yield and Improved Transplantation Outcome of Mouse Islets with Bovine Serum Albumin

Isolation and transplantation of rodent islets are frequently used as a tool for predicting the behavior of new protocols for islet allotransplants in type 1 diabetes patients. Bovine serum albumin (BSA) is recognized as a protease inhibitor possibly protecting function and viability in islets. For this study, the addition of 0.2% BSA to the isolation protocol resulted in a 30% increase in islet yields while other parameters, such as viability and function, retained high islet quality. In vivo, a minimal mass of 70 BSA treated islets showed their ability to control glycemia levels in diabetic mice by bringing the average blood glucose to ？mg/dL compared to ？mg/dL without BSA. Our results show that the simple addition of BSA to the isolation protocol constitutes a reliable and reproducible method for increasing islet yield. Also adding BSA to the transplantation medium improves islet function in vivo. The method outlined here can reduce the overall number of animals needed per experiment and also reduce the time and resources needed for islet preparation. 1. Introduction With the increased interest in finding a cure for type 1 diabetes, basic research is done with mouse models that require the isolation of islets of Langerhans from the pancreas. Several good methods of islet isolation have been described previously. Lacy and Kostianovsky method is most often referenced in which the pancreas is distended by injecting Hanks’ balanced salt solution (HBSS) into the bile duct [1]. The pancreas is removed from the mouse, cut into small pieces and digested with collagenase. They further described the use of a sucrose density gradient to facilitate purification of islets from acinar tissue. Lindall et al. proposed the use of Ficoll instead of sucrose as a separation agent with the assumption that Ficoll provided a more physiologically osmotic environment for the islets [2]. Gotoh et al. [3] improved this method by injecting the collagenase directly into the pancreas through the bile duct then separating the endocrine from the exocrine tissue with a discontinuous Ficoll gradient. With these techniques, isolation of mouse islets has become a standard procedure used in many research laboratories. However, some mouse strains lend themselves to islet isolation less well than others. Also, some genetically altered lines of mice do not breed abundantly and each mouse is therefore precious. Using mice such as these for islet studies could benefit from a way to increase the islet yield of each mouse. Additionally, reduction, refinement, and replacement (the 3Rs) of