New Islet Model for 3D Study of Endothelial and β Cell Interactions: Relevance for the Screening of Cytoprotective Agents

This protocol details an optimized method for the production of small stable spheroids, their culture, and 3D imaging, for the study of the endothelial and insulin-producing β cells interactions in a 3D model of pancreatic islets. The 150-200 µm spheroids, mirroring the lowest range of islet sizes, were prepared from a selected ratio combining 1 intra-islet endothelial cells (MS-1 cells) to 20 insulin-secreting cells (β-TC-6). Staining, clearing, and mounting challenges of small spheroids and their tackling by employing low-melting point agarose and the CUBIC clearing technique are detailed, as well as key points for an efficient analysis of the 3D structure with different probes. Data indicate that NTPDASE-ectonucleotidase 3 does not colocalize with insulin in the spheroid model, suggesting varying maturity and functional levels of β-TC6 and that the complete procedure can also be applied to isolated pancreatic islets, with clear probing of intra-islet vessels. These findings underscore the effectiveness of the 3D imaging protocol in revealing complex pancreatic cell organization and interactions within the islet model.