Restoration of hierarchical vascular architecture and vessel integrity by Ang1*. (a–c) PECAM staining of the P8 retina of normal (a), APB5-treated (b), and APB5 + Ang1*–treated (c) mice. Disorganized vascular remodeling induced by APB5 (b) was substantially restored by Ang1*, with clearer distinctions between arteries and veins (c). Note the formation of numerous capillaries and extensive anastomoses with arteries. (d–f) H&E staining of P10 retina of normal (d), APB5-treated (e), and APB5 + Ang1*–treated (f) mice. Ang1* prevented APB5-induced retinal collapse by suppression of edema and hemorrhage. (g and h) Ultrastructural analysis of the vessel walls in the retina treated with APB5 + Ang1*. Despite the absence of MCs, extraluminal fluid accumulation almost completely disappeared (g) and basement membranes were corrected to form a fine layer (arrowhead in h) as seen in the normal vessels. Note the intact integrity of the EC-EC junctions. EC, endothelial cell.