Abstract
Purpose:
Pathologic retinal neovascularization is the most common causes of vision loss in several eye diseases, such as retinal angiomatous proliferation (RAP) and macular telangiectasia (MacTel). The very low density lipoprotein receptor (Vldlr) knockout (KO) mice show pathologic retinal neovascularization in normally avascular photoreceptor layer, mimicking RAP and MacTel in human, and therefore serves as a valuable mouse model to study the mechanisms of neovascularization in both diseases. Neuronal guidance cues such as Semaphorin signaling through their receptors plexins and neuropilins, play central roles in directing both neuronal patterning and vascular growth. Previous studies suggest that Sema3F acts as an anti-angiogenic barrier in photoreceptors. In this study, we investigated whether neuronal guidance cues are affected in Vldlr knockout retinas to regulate retinal neovascularization.
Methods:
Heterozygous Vldlr mice were bred to generate Vldlr KO and littermate wild type (WT) control mice, with retinas isolated at postnatal day (P) 1, 3, 5, 7, 8, 10, 12, 17 and 21 for protein and RNA extraction. Real time PCR and Western blot were performed to analyze the expression levels of class III Semaphorins and its receptors plexins and neuropilins.
Results:
Vldlr expression levels in WT retinas gradually increases during development from P1 to P21, consistent with an important role of Vldlr in blood vessel development. Compared with WT retinas, loss of Vldlr significantly reduces retinal Sema3F mRNA levels by more than 2 fold at P1 (n=6, P<0.01), more than 5 fold at P8 (n=6, P<0.001), and > 2 fold consistently from P7-21. Other semaphorins (sema3A, 3C, 3D and 3E) are not significantly altered in vldlr ko retinas. Expression of Neuropilin 2, a receptor for Sema3F was also suppressed in Vldlr KO retinas.
Conclusions:
These results indicate that retinal VLDLR deficiency suppresses anti-angiogenic Sema3F, which may promote pathologic retinal neovascularization observed in Vldlr KO mice.
Keywords: 609 neovascularization •
700 retinal neovascularization