Long-Term Expansion of Pancreatic Islet Organoids from Resident Procr+ Progenitors

It has generally proven challenging to produce functional beta cells in vitro. Here, we describe a previously unidentified protein C receptor positive (Procr(+)) cell population in adult mouse pancreas through singlecell RNA sequencing (scRNA-seq). The cells reside in islets, do not express differentiation markers, and feature epithelial-to-mesenchymal transition characteristics. By genetic lineage tracing, Procr(+) islet cells undergo clonal expansion and generate all four endocrine cell types during adult homeostasis. Sorted Procr(+) cells, representing similar to 1% of islet cells, can robustly form islet-like organoids when cultured at clonal density. Exponential expansion can be maintained over long periods by serial passaging, while differentiation can be induced at any time point in culture. beta cells dominate in differentiated islet organoids, while alpha, delta, and PP cells occtat lower frequencies. The organoids are glucose-responsive and insulin-secreting. Upon transplantation in diabetic mice, these organoids reverse disease. These findings demonstrate that the adult mouse pancreatic islet contains a population of Procr(+) endocrine progenitors.