Long-term culture of human pancreatic islets reveals reduced metal ion pathways in their gene signature.

Pancreatic islet transplantation is an effective therapy for type 1 diabetes; however, its broader clinical application is limited by the shortage of donors. Establishing long-term culture methods for isolated islets is an area of ongoing investigation that may ultimately support applications such as biobanking and stem cell-derived islets. However, maintaining transplantable quality of islets during extended culture remains a challenge. We recently developed a method for human islet culture on optimally sized microwells that preserves viability over two weeks. Despite improved viability, other key pre-transplantation factors, such as islet metabolism, remained reduced, indicating a need for further optimization. To identify potential targets for improvement, we performed RNA sequencing on human islets from three deceased donors, comparing two-week cultures (microwell and conventional) versus pre-culture controls. Transcriptomic analysis showed significant gene expression changes in two-week-cultured islets compared to pre-culture islets, whereas microwell and conventional culture conditions showed minimal differences despite improved viability in microwell culture. Pathway analysis revealed that long-term culture consistently downregulates heavy metal ion-related pathways, particularly zinc-related pathways regulated by metallothioneins. This suggests a loss of β-cell characteristics during extended culture. Our findings highlight intra-islet metal ion homeostasis as a potential therapeutic target for improving transplantation outcomes following prolonged islet culture.