PURPOSE. Choroidal neovascularization (CNV) is a severe complication of AMD. The Wnt signaling pathway has been shown to mediate angiogenesis. The purpose of this study was to investigate the pathogenic role of the Wnt pathway in CNV and explore the therapeutic potential of a novel Wnt signaling inhibitor in CNV.METHODS. Adult rats and mice were photocoagulated using diode laser to induce CNV. On the same day, the animals were intravitreally injected with a monoclonal antibody (Mab2F1) blocking LRP6 or nonspecific mouse IgG. The Wnt signaling activation and target gene expression in the eyecup were determined by Western blot analysis. Fundus angiography was used to examine leakage from the laser lesion. CNV areas were measured on choroidal flatmount using FITC-dextran. The canonical wingless-type MMTV integration site (Wnt) signaling pathway plays a critical role in the regulation of inflammation and angiogenesis. 5,6 Wnt ligands are secreted, cysteine-rich glycosylated proteins, 3 which bind to frizzled (Fz) receptors or to the coreceptor complex of Fz and low-density lipoprotein receptor-related protein 5 or 6 (LRP5/6).
RESULTS. Levels of
4-6Binding of Wnt ligands results in LRP6 phosphorylation and activation, 7,8 leading to dissociation of the kinase complex containing glycogen synthase kinase-3b (GSK3b), 9 axin and adenomatous polyposis.3 The GSK3b complex dissociation prevents transcription factor b-catenin from phosphorylation and degradation.10 Consequently, b-catenin is accumulated in the cytoplasm and translocated into the nucleus, complexes with TCF/LEF family transcription factors, 11 regulating expression of Wnt target genes including VEGF, which is the key pathogenic factor in CNV. [12][13][14][15] Although studies of the pathogenesis and treatment of AMD have been delayed by lacking of ideal animal models, 16 laserinduced CNV rodent models are commonly used to study CNV in wet AMD. [17][18][19][20] Moreover, our previous study has shown that the Wnt signaling pathway is activated in very low-density lipoprotein receptor (VLDLR) knockout (KO) mice, a genetic animal model of subretinal neovascularization (NV). 21 The present study investigated the role of the Wnt signaling pathway in laser-induced CNV and explored therapeutic potential of a blocker of Wnt signaling in laser-induced CNV and VLDLR KO models.
METHODS AnimalsCare, use, and treatment of experimental animals were in strict agreement with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Male C57BL/6J mice and VLDLR KO mice (10 weeks old; The Jackson Laboratory, Bar Harbor, ME) and male Brown Norway rats (8-10 weeks old; Charles River, Wilmington, MA) were used in this study. In all procedures, animals were anesthetized by intramuscular injection of 50 mg/kg ketamine hydrochloride (Vedco, St. Joseph, MO) and 10 mg/kg xylazine (Vedco), and pupils were dilated with topical administration of 1% cyclopentolate (Wilson, Mustang, OK).
CNV InductionLaser photocoagulation (532 nm, 150-250 mW, 0.01 second, 50 lm; model di...