A comparative evaluation of culture conditions for short-term maintenance (<24 hr) of human islets isolated using the Edmonton protocol

Once human islets are isolated, they are typically transplanted into type 1 diabetic recipients within 2 h of isolation. This time restriction makes it difficult for patients to travel from distant locations to receive an islet transplant and it also makes it difficult to complete pre-release quality control assessments (i.e., endotoxin and gram stain) before the expiration of the islet product. Therefore, there were two goals for this study. The first was to measure the stability of islets after a 24 h culture period using CMRL media 1066 (CMRL) supplemented with either fetal bovine serum (FBS); albumin or insulin transferrin and selenium (ITS). The second was to determine the impact of cell concentration and media depth on islet stability. The results of the study indicated that culture recoveries at 37 °C with CMRL + ITS (also known as Memphis media) were higher (64.1 ± 8.3%) than with CMRL supplemented with FBS (38.7 ± 9.7%) or albumin (47.6 ± 8.2%) and that post-culture islet viabilities, post-culture purities and stimulation indexes (SIs) were comparable. In the second series of experiments, the results showed that islets recoveries and SIs in cultures with low islet concentrations (300 IE/ml) were significantly better than cultures at high islet concentrations (1500 IE/ml). Additionally, at a shallow media depth (1.4 vs. 7 mm of media) the SI of the islets improved, and this effect was independent of the additive (i.e., FBS, albumin and ITS).