Introduction: The islet basement membrane (BM) is a specialized sheet of extracellular matrix comprised primarily of laminins, collagen IV and perlecan. It is essential for islet function and survival. During the enzymatic digestion phase of islet isolation, the islet BM is significantly disrupted. Further loss of the islet BM occurs during the mandatory culture period, when islets are placed in CMRL media at 37°C. Previous studies have demonstrated the superiority of UW cold storage solution for maintaining islets during the post-isolation culture period. However, the impact of UW storage on BM integrity during culture has not been explored. We hypothesize that the increased viability and recovery of islets following culture in UW, may be due to the preserved integrity of the islet BM. 

Methods: Isolated human Islets (n=4) were divided into two groups, and cultured for up to 72hours in either: CMRL media at 37°C or; UW at 4°C. Islet samples were collected every 24hours from each condition, which included collection of a post-isolation sample. Samples were assessed for purity, viability and islet yield. BM integrity was determined histologically via insulin and laminin labeling. Total protein concentration was determined by ELISA. Results from the cultured samples were normalized to the post-isolation sample. Statistical analysis was by way of ANOVA, with data presented as average ± standard deviation. 

Results: Islet viability significantly declined following culture in CMRL at 48 and 72 hours (reduction of 26±5%, and 25±3%, both p<0.001). There was no significant loss of viability for islets stored in UW, for up to 72hours. Following 72hours of culture, the remaining number of islets stored in CMRL were significantly lower than those stored in UW (p<0.05). At the molecular level, storing islets in CMRL resulted in a significant loss of total laminin at 24hours (49±12%, p<0.05), with further loss by 72hours compared to post-isolation (71±12%, p<0.001). Interestingly, storage of islets in UW led to minimal loss of laminin, which was maintained up until 72hours. These laminin profiles were supported by the corresponding histology data. 

Conclusion: UW is significantly superior to CMRL for maintaining islets for up to 72hours. The islet BM (measured via laminin) is significantly more stable in UW storage solution, compared to CMRL. The impact of UW storage on other key BM proteins are currently underway. Increased islet BM survival provides important structural evidence, which could underpin the reasons for the enhanced islet survival seen in UW culture systems.