Stem-Cell-Derived Islets as a Model of Human Islet Inflammation: A Comparative Analysis of Pro-inflammatory Cytokine Responses
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Background
Inflammation-induced pancreatic islet-cell death and dysfunction are key aspects of both type 1 and type 2 diabetes. Stem cell-derived islets (SC-islets) are an emerging tool in diabetes research, however, our understanding of how inflammation affects SC-islet function is incomplete. We therefore aimed to thoroughly characterize how SC-islets respond to pro-inflammatory cytokines at the functional and transcriptomic levels in comparison with human primary islets and EndoC-βH5 cells.
Method
A 7-stage differentiation protocol was used to generate SC-islets with insulin-, glucagon-, and somatostatin-positive cells. SC-islets, primary human islets and EndoC-βH5 cells were exposed to different doses of pro-inflammatory cytokines (IL-1β + IFNγ + TNFα) including a high dose for up to 48 h and a low dose up to 144 h to mimic the intense islet inflammation in T1D and chronic low-grade inflammation in T2D, respectively. Differential gene expression (RNA-seq), cell death, activation of key signalling proteins, hormones, and chemokine secretion were determined.
Results
Basal expression of key islet-cell identity genes in SC-islets correlated well with that of primary islets and EndoC-βH5 cells. In SC islets, cytokines dose-dependently induced activation of key proximal signalling pathways (NFκB, STAT1, and JNK), upregulation of major histocompatibility complex (MHC) class I, and increased cell death (cytotoxicity and caspase 3/7 activity). In head-to-head experiments, SC-islets displayed similar cytokine responses particularly as primary islets regarding induction of cell death, chemokine secretion, differential gene expression, and protein levels of cell death executioners (gasdermin D and caspase-7). Cytokines increased insulin release in SC-islets and primary islets, while diminishing insulin secretion in EndoC-βH5 cells. Cytokines reduced glucagon release in SC-islets, which was partially restored by treatment with the incretin hormone glucose-dependent insulinotropic peptide (GIP) with or without a glucagon-like peptide 1 (GLP-1) receptor agonist (liraglutide).
Conclusion
SC-islets are highly responsive to inflammation with a high degree of similarity to primary islets. Our results support the use of SC-islets as a valid tool in inflammation and diabetes research.
