Ad.hVEGF-A treatment results in clear irregularities in endothelial morphology and arrangement. CD31 staining in Ad.empty–treated (A,C) and Ad.hVEGF-A–treated (B,D) plaques shows weakly stained microcapillaries in advanced carotid artery lesions. VEGF-A does induce endothelial cell sprouting from the lumen to the central atheroma in Ad.hVEGF-A–treated plaques (D); these endothelial irregularities are not observed in Ad.empty–treated plaques. Panels C and D are high-power views of the vessel segments shown in panels A and B, respectively. Original magnification: panels A and B, ×40; panels C and D, ×100.