Quantitative and qualitative standards for islet isolation assessment in humans and large mammals

Several procedures have been recently developed to separate and purify pancreatic islets from large mammals, including humans. It is often difficult to interpret and compare results, mainly because of lack of standardization of criteria for Islet Isolation Assessment (IIA). In small animals, such as rodents, it is generally not a problem to identify and count all the islet tissue retrieved, due to the small numbers with which we are dealing in these species. In larger mammals, several hundred thousand islets can be obtained from a single pancreas, making it critical to correctly sample, identify, count, and verify insulin-producing tissue. The purpose of this workshop was to discuss and determine minimal, simple requirements for IIA, not to indicate absolute parameters for islet count, purity, or function. Both quantitative and qualitative criteria for IIA have been discussed, the main topics being determination of islet number, islet volume, purity of final preparations, documentation of morphologic integrity, viability tests, in vitro function studies (static incubation and perifusion), and in vivo function studies after transplantation in diabetic athymic rodents.