Choroidal neovascularization (CNV) in AMD is a leading cause of vision loss. Oxidative stress and inflammation in the retina and RPE are believed to play important pathogenic roles in CNV. The canonical Wnt pathway is known to mediate inflammation, angiogenesis and fibrosis. Our previous studies have shown that very low-density lipoprotein receptor (VLDLR) knockout (KO) results in Wnt pathway over-activation, retinal inflammation and sub-retinal neovascularization (NV). Our recent study demonstrated that the Wnt pathway is also over-activated in the laser-induced CNV model, and blockade of Wnt signaling attenuated NV in Vldlr-/- mice and the laser-induced CNV. This project will extend our ongoing studies and use Wnt signaling reporter mice to further verify the activation of Wnt signaling in the retina and RPE of Vldlr-/- mice and laser-induced CNV model. We will also knockout -catenin, an essential effector of Wnt signaling, in the RPE to determine if interruption of Wnt signaling attenuates NV in these models. These studies will establish the pathogenic role of aberrant regulation of Wnt signaling in CNV and reveal a novel therapeutic target. There are two major alternative splicing variants of VLDLR, VLDLR1 and VLDLR2. Our preliminary data showed that the retina expresses exclusively VLDLR2 which has higher ectodomain shedding into the extracellular space than VLDLR1. VLDLR2 is known to have lower affinity to VLDL, and its function in the retina is unclear. We will test the hypothesis that soluble VLDLR ectodomain (sVLDLRN) shed into the extracellular space and circulation may function as a soluble inhibitor of Wnt signaling and modulates Wnt signaling through dimerization with LRP6, an essential co-receptor in the Wnt pathway. The inhibitory effects of sVLDLRN and its deletion peptide fragments on Wnt signaling and on CNV will be evaluated in vitro and in vivo. This project will investigate if VLDLR2 has more potent inhibition of Wnt signaling, compared to VLDLR1, due to its higher ectodomain shedding. These studies will reveal a new function of VLDLR2 in the retina. This project will establish the receptor ectodomain shedding and receptor:receptor dimerization as a new mechanism for modulation of the Wnt pathway. The proposed studies will also explore a novel pathogenic mechanism for CNV in AMD models and reveal a new therapeutic target. Identification of the peptide fragment of VLDLR with anti-angiogenic activity in this project has potential to develop a therapeutic drug for CNV.
The major goal of this project is to study pathogenic mechanisms responsible for choroidal neovascularization (CNV) in age-related macular degeneration (AMD). Since CNV is a major cause of blindness in aged population, this project will enhance our understanding of this blinding disorder. The information generated from this study will also reveal a new drug target for the treatment of CNV and prevent vision loss in AMD patients. This project has potential to develop a peptide inhibitor of angiogenesis that can be used for the treatment of CNV.
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