Loss of Endosialin results in increased vessel density. Retinas from littermate Endosialin^+/+, Endosialin^+/−, and Endosialin^−/− C57BL/6 mice were stained with FITC–isolectin B4 and NG2 followed by Alexa Fluor 555–anti–rabbit Ig. (A) Low-power images of P4 retinas with box indicating the field of view in the central capillary plexus analyzed for quantification of vessel density in panels B and C. (B) Quantification of vessel density (Metamorph software tool)/100 μm² ± SEM. (C) Quantification of vessel density (manual counting of branch points)/100 μm² ± SEM. Endosialin^+/+: P2, n = 5; P3, n = 7; P4, n = 5; P7, n = 3. Endosialin^+/−: P2, n = 5; P3, n = 4; P4, n = 5; P7, n = 7. Endosialin^−/−: P2, n = 4; P3, n = 4; P4, n = 5; P7, n = 5. (D) Confocal images of P4 retinas to illustrate no difference in NG2-positive pericyte coverage in Endosialin^+/+, Endosialin^+/−, and Endosialin^−/− mice. a indicates arteries; and v, veins. Scale bar indicates 200 μm.