Neuropilin-1 expression by endothelial cells and retinal pigment epithelial cells in choroidal neovascular membranes

PURPOSE: To determine if vascular endothelial growth factor (VEGF) coreceptor neuropilin-1 (NP-1) is expressed in choroidal neovascularization (CNV) and to localize the expression. DESIGN: Laboratory investigation. METHODS: Six CNV membranes (CNVMs) obtained from patients with subfoveal CNV attributable to age-related macular degeneration (AMD) underwent immunohistochemistry for VEGF receptor-2 (VEGFR-2) and NP-1. The positive cell types were identified by double staining with anticytokeratin, anti-CD31, and antismooth muscle actin (SMA). RESULTS: Immunohistochemical staining revealed positivity for VEGFR-2 and NP-1 in all six CNVMs. Both receptors were strongly expressed by new choroidal endothelial cell forming vessels and CD-31-positive cells in the nonvascular area. They were also expressed in the pigmented retinal pigment epithelial layer and by cytokeratin-positive, nonpigmented retinal pigment epithelium cells in the nonvascular area. The nonpigmented retinal pigment epithelium cells positive for VEGFR-2 and NP-1 were highly colocalized with SMA. CONCLUSIONS: The presence of both VEGF and NP-1 suggest that NP-1 may play a role in the evolution of CNV in AMD.