Generation of functional islet-like clusters after monolayer culture and intracapsular aggregation of adult human pancreatic islet tissue.

Background. Cellular replacement therapy represents a promising strategy for treating type I diabetes; however, such an approach is limited due to the inadequate availability of human donor tissue. Here we investigated the extent to which human islet tissue can be expanded in monolayer culture and brought back to islet function. Methods. Adult human pancreatic cells were proliferated with a serum-free media in monolayer cultures through multiple passages. Expanded cells were dispersed and encapsulated in alginate-poly-L-lysine microcapsules wherein the cells spontaneously coalesced into islet-like clusters. Encapsulated cell clusters were subsequently transplanted into the peritoneal cavity of streptozotocin -induced diabetic severe combined immunodeficiency mice. Results. The cultured monolayer cells secreted insulin in response to glucose stimulation and maintained endocrine gene expression. Encapsulated islet-like clusters displayed cellular architecture similar to freshly isolated and encapsulated adult human islets maintained in culture, exhibiting an immunoreactive core of insulin, glucagon, and somatostatin, as well as peripheral cytokeratin-19 staining. Encapsulated aggregates significantly reduced hyperglycemia in transplanted mice within I week and normoglycemia was achieved after 5 weeks. Human C-peptide was detected in transplanted mice concomitant with the reduction in hyperglycemia. Capsules recovered 8 weeks posttransplantation exhibited insulin immunoreactivity. Conclusions. Collectively, these data indicate that adult human pancreatic islet cells can be expanded by three serial passages while maintaining their endocrine properties and can yield functional islet-like cell clusters through intracapsular aggregation that reverse hyperglycemia in diabetic mice. This culture and aggregation process could serve as a platform for proliferation and differentiation studies of endocrine lineage cells.