Functional Maturation and Glucose Responsiveness in Stem Cell-Derived β Cells

Abstract

Stem Cell-derived β cells (SC-β cells) are an unlimited source of islet-like material for curative transplantation in patients with Type 1 Diabetes. SC-β cell potential to supplement or replace human islets for transplantation is limited by their ability to sense changes in glucose levels and respond by secreting insulin to restore normoglycemia. SC-β cells respond to glucose in vitro, but at a magnitude lower than that of human islets. We have analyzed their capability to sense glucose and undergo glucose stimulated insulin secretion (GSIS) in vitro and identified a novel bottleneck in glycolysis, limiting their potential to undergo GSIS. Bypassing this deficiency in metabolism results in an insulin secretion profile indistinguishable from human islets. SC-β cell glucose sensing also improves after transplantation. To study this process, we have analyzed gene expression changes before and after transplantation into immune-compromised mice. In addition to identifying changes in pathways regulating insulin secretion, we have identified Islet Amyloid Polypeptide (IAPP) as a potential marker of more mature SC-β cells. Using a dual knock-in fluorescent reporter line, we have characterized the dynamics of the IAPP-expressing SC-β cell subpopulation before and after transplant, demonstrating IAPP expression marks a more mature, stable population of SC-β cells in vitro. In summary, we have identified a glycolytic defect in SC-β cells limiting their function in vitro. Bypassing this defect will assist in generating SC-β cells for cell-based therapies for diabetic patients. Analysis of gene expression during in vivo functional maturation of SC-β cells revealed IAPP expression is characteristic of more mature SC-β cells in vitro and has provided a new marker for SC-β cells during differentiation.