A Novel Islet-PBMC Co-Culture Model For Studying Type 1 Diabetes

Type 1 diabetes (T1D) is primarily characterized by immune-mediated destruction of pancreatic beta-(β)-cells resulting in loss of insulin production. Its incidence is significantly increasing in developed countries and there is currently no prevention or cure. Existing rodent and in vitro models lack many functions critical for understanding the onset and progression of this disease in humans. Although isolated primary islets are considered the in vitro gold standard of diabetes research, they present multiple limitations to their experimental use due to their inherent heterogeneity in size, cellular composition, function, and purity, as well as a rapid functional decline (glucose-responsiveness) and viability. The current study investigated the use of a novel co-culture platform comprising peripheral blood mononuclear cells (PBMC) and uniform 3D human islet microtissue. The microtissues, produced using an optimized dissociation protocol and controlled scaffold-free reaggregation of primary islet cells, were cultured one-islet per well in 96-well plates, and unstimulated and anti-CD3/CD28-stimulated HLA-matched PBMC were cultured together, with or without inflammatory cytokines. The microtissues displayed uniform, long-term (>28 days), and robust viability and function enabling high-throughput and longitudinal study of immune cell-endocrine cell interactions and β-cell function. Cultures of naïve PBMCs and islet microtissues had no impact on β-cell function; however, combination of activated PBMCs and islet microtissues resulted in a PBMC number-dependent decline in islet health demonstrated by decreased stimulated insulin secretion, insulin content, and PDX-1⁺ nuclei count within each microtissue. The observed destruction correlated with the amount of CD3⁺ cells infiltrating the islet microtissues and was significantly increased by cytokine preconditioning of the islets. The established platform serves as a valuable biomimetic islet model that may allow for better understanding of T1D progression and immune-islet interaction, as well as for screening compounds that could prevent immune-cell mediated destruction of islets.