Role of VEGF-A in Vascularization of Pancreatic Islets Eckhard Lammert, Guqiang Gu, Margaret McLaughlin, Dennis Brown, Rolf Brekken, Lewis Charles Murtaugh, Hans-Peter Gerber, Napoleone Ferrara, Douglas A. Melton  Current Biology  Volume 13, Issue 12, Pages 1070-1074 (June 2003) DOI: 10.1016/S0960-9822(03)00378-6

Figure 1 Islet Development Adjacent to Pancreatic Blood Vessels Is Independent of VEGF-A Levels (A and B) VEGF-A-deficient islets (−/−) were either located directly adjacent to the vessels or separated from vessels by a few cell diameters. (C and D) Compared with wild-type (wt) islets (C), VEGF-A-deficient (−/−) islets (D) had a reduced number of capillaries. Insulin was stained green, PECAM1/CD31 (an endothelial cell marker) was stained red, and DAPI (a cell nucleus marker) was stained blue in these light-microscopic images. Scale bars represent 50 μm. (E) In the −/− pancreas, the number of endothelial cells (ECs) is reduced in contrast to the islet cells. In brief, 30 pancreas sections of mice of each genotype (n = 3) were stained for PECAM1 and insulin to determine what percentage of the total pancreas area is stained or made up of endothelial cells and β cells, respectively. ECs inside of islets and ECs attached to the outside of islets were used for “% EC area in islets.” NIH image was used for measuring the areas of scanned images. Current Biology 2003 13, 1070-1074DOI: (10.1016/S0960-9822(03)00378-6)

Figure 2 VEGF-A Is Required for the Endothelial Cell Morphology of Islets (A and B) Electron-microscopic images show a capillary surrounded by pancreatic β cells in wild-type (A) and −/− (B) islets. (C and D) Magnifications of the upper panel (A and B) are shown for wild-type (C) and −/− (D) islets. BM, basement membrane; SG, secretory granule; islet cell = pancreatic β cell as determined by its location inside of islets and the large halos, which surround most of the insulin granules. Scale bars represent 1 μm. (E and F) An EC body of a wild-type islet (E) and −/− islet (F) is shown. Arrowheads point to fenestrae (E) and caveolae (F). Scale bars represent 100 nm. (G) The numbers of fenestrae and caveolae found on 3 μm EC body inside of pancreatic islets are shown. Six islets of each genotype were used for determining these numbers. Nuclear regions on EC were excluded from the calculation. Current Biology 2003 13, 1070-1074DOI: (10.1016/S0960-9822(03)00378-6)

Figure 3 VEGFR2 Expression on Islet Endothelium Electron-microscopic images show an islet cell adjacent to a capillary formed by an EC (upper left corner). The presence of black DAB reaction product in the EC indicates the presence of antigenic sites for the markers indicated. (A) Islet stained for the platelet-endothelial cell adhesion molecule PECAM1. (B) Islet stained for the vascular endothelial growth factor receptor VEGFR2. (C) Islet stained with no primary antibody as a control. Scale bars represent 0.5 μm. Current Biology 2003 13, 1070-1074DOI: (10.1016/S0960-9822(03)00378-6)

Figure 4 Blood Glucose Regulation Defects without Islet VEGF-A (A) Glucose tolerance tests revealed a defective blood glucose regulation in −/− mice. N = 8 2-month-old male mice of each genotype; asterisks indicate p values < 0.005. (B) Blood glucose levels in mg/dl after 16 hr of starvation (before glucose challenge) and 3 hr after glucose challenge reveal a response to elevated blood glucose levels in −/− mice. N = eight male mice of each genotype. (C and D) Electron microscopic images show an islet cell adjacent to a capillary (upper left corner). The presence of black DAB reaction product in the EC indicates the presence of antigenic sites for PECAM1 in wild-type (C) and −/− (D) islets. (D) An islet cell granule, which appeared to be taken up by an EC, is labeled with an arrowhead. EC-incorporated granules were occasionally observed in −/− islets (1–3 granules per −/− islet), but not inside of wild-type islets. SG, secretory granules. Scale bars represent 0.5 μm. Current Biology 2003 13, 1070-1074DOI: (10.1016/S0960-9822(03)00378-6)