Differential expression patterns of Semaphorin 3F in the murine and human retina and its role in choroidal neovascularization

Abstract

Purpose: Semaphorins A-F (Sema A-F) play an important role in neuronal guidance and angiogenesis. Sema3F is an inhibitor of blood vessel development. We investigated retinal expression of Sema 3F during normal retinal development in mice and in the adult human retina. The influence of Sema 3F on choroidal neovascularization (CNV) was investigated in vitro.

Methods: Eyes from wild type C57BL/6 mice were analyzed using immunohistochemistry, laser capture microdissection, qPCR and Western Blot for Sema3F at postnatal day P3, P17 and P60. Immunohistochemistry for Sema3 F was performed in adult human retinas. For functional in vitro analysis, choroidal explants (CE) from wild type C57BL/6 mice were placed in collagen matrix and stimulated with VEGF 165. Recombinant Sema3F was added to the matrix.

Results: qPCR expression analysis following laser capture microdissection revealed that Sema3F was mainly expressed in photoreceptors and retinal pigment epithelium (RPE). Western Blot analysis confirmed strong Sema3F expression in RPE. This expression pattern was confirmed by immunohistochemistry where robust staining of Sema3F localized to the photoreceptor/RPE interface. These expression patterns were stable at all time points investigated in mice and were confirmed by immunohistochemistry in adult human retinas. Consistent with a role in outer retinal homeostasis, Sema 3F significantly reduced angiogenic sprouting in VEGF-stimulated CE (p= 0.01).

Conclusions: Our data suggests that deregulation in Sema3F levels may play a role in diseases affecting the outer retina, e.g. age-related macular degeneration. The reduced angiogenic sprouting in Sema3F- stimulated CE suggests that Sema3F may play a role in maintaining the physiologic avascularity of the outer retina.

Keywords: 453 choroid: neovascularization • 412 age-related macular degeneration • 688 retina