A C57BL/6N mice pups at P3 received 1 μg of mouse Sema3C-Fc (right eye) or control IgG-Fc (left eye). The retinal vasculature was examined at P5 by whole-mount CD31immunofluorescence staining. Representative images show the total retinal vasculature and sprouting tips at the vascular front (iii and iv, arrows) and the enlarged intercapillary space (ii and iv, asterisks). Scale bar, 100 μm and 20 μm (iii and iv).B,C (B) Retinal vessel outgrowth measured as the total area from the central optic disk to the vascular front normalized to control IgG-Fc treatment, ***P = 0.0009. (C) Vessel density was quantified by CD31-stained vessels and normalized to the total vessel area, ***P = 0.0002. (Mean ± s.e.m; n = 23 retinae in each group from four independent experiments; unpaired Student's t-test.)D,E (D) Number of sprouting tips per retina, *P < 0.0001. (E) Branch points in the capillary plexus represented as the ratio to the control IgG-treated retinae, ***P < 0.0001. (Mean ± s.e.m; n = 18 retinae in each group from three independent experiments; unpaired Student's t-test.) 