Fig. 2

Cyto-architecture of delta cells in rodents and human islets. Delta cells send out cellular processes (filopodia) to increase their intra-islet reach. Maximum projection images of representative mouse (a) and a human delta cells (b) immunostained with anti-somatostatin antibodies. The yellow arrowheads indicate cellular extensions from delta cells. c Scanning electron microscopy of a human islet. Somatostatin-expressing delta cell is highlighted by a purple shade. Right, close-up image of the delta cell filopodia (highlighted by the cyan box in c) contacting an alpha and a beta cell. d Physical length of the delta cell filopodia in its longest axis (tip to cell body) in vivo in mouse islets (empty black circles, n = 47 cells) and in PFA-fixed pancreases from mice (black circles, n = 31 cells) and human (pink circles, n = 57 cells) samples. e Relative reach of single delta cells towards alpha and beta cells in mouse (black line) and human islets (purple line). f In vivo longitudinal follow up of a single delta cell at 10-min intervals or 19 h later. Delta cells were from SST-ChR2 islets and imaged with TPM to avoid rhodopsin activation²⁸. A yellow line highlights the delta cell morphology over time. g In vivo longitudinal follow up of a single delta cell filopodium over the course of 4 days as in f. Vessels were visualized by an i.v. injection of TRITC-labeled dextran molecules. Yellow arrowheads indicate the filopodium from the same delta cell from days 1 to 4. h Delta cell filopodia length from isolated islets treated with insulin, IGF, and VEGF-A with or without the IGF-1R receptor blocker picropodophyllin (PPP) or the VEGFR blocker Axitinib. Statistics shown for FDR (q < 0.005 for discovery): *q = 0.052, p = 0.0284; **q < 0.002, p < 0.001, ^#q < 0.002, p < 0.001 vs control (DMSO) group. Detailed statistics shown in Supplementary Data 1. Error bars represent the 95% confidence interval (C.I.) of the mean. For d, e, and h, source data are provided as a Source Data file