Targeting ESM-1 by siRNA inhibits VEGF-A effects on lymphatic vessels in vivo. Differential immunostains for CD31 (red) and LYVE-1 (green) reveal that, compared with Matrigels that contain PBS (control) (A), LYVE-1⁺ lymphatic vessels (green) surrounding Matrigels containing VEGF-A and control siRNA were enlarged (B). Lymphatic vessels were not enlarged surrounding Matrigels containing VEGF-A and ESM-1 siRNA (C). Scale bars equal 100 μm. Computer-assisted morphometric analyses of LYVE-1/CD31–stained sections showed comparable density of lymphatic vessels in all groups (D). The mean size of lymphatic vessels was significantly larger surrounding Matrigels containing VEGF-A and control siRNA (Ctrl-siRNA) than Matrigels containing PBS (control) (E) or VEGF-A and ESM-1 siRNA (ESM1-siRNA). The mean tissue area covered by lymphatic vessels was significantly increased surrounding VEGF-A/Ctrl-siRNA implants compared with PBS-containing (control) or VEGF-A/ESM1-siRNA–containing implants (F). *P < .05; **P < .005; ***P < .001.