Directed differentiation of pancreatic d cells from human pluripotent stem cells

Human pancreatic d cells maintain the balance of pancreatic hormones and loss of d cells or disruption of somatostatin release is associated with diabetes. Despite their important role, human d cells are scarce (~5% within the islets), limiting physiological studies and drug discovery targeting d cells. To date, no directed d-cell differentiation method has been established. In this study, we established a link between fibroblast growth factor (FGF) signaling pathways and pancreatic d-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 d-cell lineage by inducing the expression of SST and the d-cell specific transcription factor HHEX, via FGF receptor 1(FGFR1). We developed a differentiation method to generate d 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 d 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 d cells from human stem cells in vitro would provide an unprecedented cell source for drug discovery and cell transplantation studies in diabetes. Overall design: H1 ES cells were differentiated into delta cell-containing islet organoids. The Islet organoids were collected at S7D14 and analysed by scRNA-seq.