Intra-islet endothelial cell and β-cell crosstalk: Implication for islet cell transplantation

Figure 1 A model demonstrating the intra-islet endothelial cell and β-cell crosstalk. A: An image of freshly isolated human islets; B: Immunohistochemical staining of an islet demonstrating intra-islet vessels stained with CD31 (brown); C: Schematic representation of different cells within an islet along with intra-islet vessel fragments; D: A three dimensional (3D) depiction of islet cells and how these surround the intra-islet vessels, which are a group of endothelial cells arranged into a tube like structure; E: A model demonstrating a cross-talk relationship between endothelial cells and β-cells mediated by various endocrine factors/molecules. VEGFs, angiopoietins, insulin, cell surface molecules including ephrins mainly produced by the β-cell, are important factors for endothelial cell proliferation. Endothelium-derived factors such as hepatocyte growth factor, thrombospondins, basement membrane components (laminins, collagens) improve β-cell survival and promote insulin transcription and secretion. Other EC-derived factors include fibroblast growth factor and the vasoconstrictive endothelin-1. VEGF: Vascular endothelial growth factor; EC: Endothelial cell.