Expression of neuropilin-1 in choroidal neovascular membranes

Background: Neovascularization is a serious consequence of several eye diseases, including age-related macular degeneration. Neovascularization is under the control of proangiogenic factors, such as vascular endothelial growth factor and fibroblast growth factor. Recent work in our laboratory has focused on other, novel angiogenic factors, such as neuropilin-1, and their potential role in neovascularization. The purpose of this study was to investigate the role of neuropilin-1 in choroidal neovascularization (CNV). Methods: We examined the localization of neuropilin-1 by immunohistochemistry in nine choroidal neovascular membranes (CNVMs) surgically excised from four patients with age-related macular degeneration who had not undergone laser photocoagulation, four with idiopathic CNV and one with ocular histoplasmosis. We also stained the membranes for markers of endothelial and retinal pigment epithelial cells. Controls included omission of primary antibody, use of an irrelevant primary antibody, and neuropilin-1 staining of the posterior sclera, choroid and retina of four healthy donor eyes. Results: Neuropilin-1 was present in eight of the nine CNVMs. It was localized mainly to the plasma membrane. The more vascular membranes and those consisting of a larger number of retinal pigment epithelial cells were associated with greater neuropilin-1 staining. Neuropilin-1 was not seen in the posterior segment of the four healthy eyes. Interpretation: Neuropilin-1 appears to play an active role in CNV. Further study is needed to establish a causal relation.