Directed differentiation of pancreatic δ cells from human pluripotent stem cells

Human pancreatic δ cells maintain the balance of pancreatic hormones and loss of δ cells or disruption of somatostatin release is associated with diabetes. Despite their important role, human δ cells are scarce (~5% within the islets), limiting physiological studies and drug discovery targeting δ cells. To date, no directed δ-cell differentiation method has been established. In this study, we established a link between fibroblast growth factor (FGF) signaling pathways and pancreatic δ-cell lineage specification. FGF7 helped maintain a pancreatic endoderm/progenitor state with higher expression levels of PDX1 and CHGA, whereas FGF2 biased cells towards the pancreatic δ-cell lineage by inducing the expression of SST and the δ-cell specific transcription factor HHEX, via FGF receptor 1(FGFR1). We developed a differentiation method to generate δ cells from human stem cells by combining FGF2 with FGF7, which synergistically directs pancreatic lineage differentiation and modulates the expression of transcription factors and SST activators during endoderm/endocrine precursor induction. These δ cells display mature RNA profiles and fine secretory granules, secrete somatostatin in response to various stimuli, and suppress insulin secretion from in vitro co-cultured b cells and mouse b cells upon transplantation. The generation of somatostatin-secreting pancreatic δ cells from human stem cells in vitro would provide an unprecedented cell source for drug discovery and cell transplantation studies in diabetes. H1 ES cells were differentiated into delta cell-containing islet organoids. The Islet organoids were collected at S7D14 and analysed by scRNA-seq.