ENTPD3 Marks Mature Stem Cell Derived Beta Cells Formed by Self-Aggregation in Vitro

Stem cell derived beta-like cells (sBC) carry the promise of providing an abundant source of insulin-producing cells for use in cell replacement therapy for patients with diabetes, potentially allowing widespread implementation of a practical cure. To achieve their clinical promise, sBC need to function comparably to mature adult beta cells, but as yet they display varying degrees of maturity. Indeed, detailed knowledge of the events resulting in human beta cell maturation remains obscure. Here we show that sBC spontaneously self-enrich into discreet islet-like cap structures within <i>in vitro</i> cultures, independent of exogenous maturation conditions. Multiple complementary assays demonstrate that this process is accompanied by functional maturation of the self-enriched sBC (seBC); however, the seBC still contain distinct subpopulations displaying different maturation levels. Interestingly, the surface protein ENTPD3 (also known as nucleoside triphosphate diphosphohydrolase-3 (NDPTase3)) is a specific marker of the most mature seBC population and can be used for mature seBC identification and sorting. Our results illuminate critical aspects of <i>in vitro</i> sBC maturation and provide important insights towards developing functionally mature sBC for diabetes cell replacement therapy.