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K. Lee, Y. Chen, Y. Hu, J.-X. Ma; Inhibitory Effects of an Anti-lrp6 Monoclonal Antibody on the Canonical Wnt Pathway and Vascular Permeability. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4512.
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Our previous studies have shown that the canonical wnt signaling plays a major pathogenic role in age-related macular degeneration and diabetic retinopathy through mediating over-expression of angiogenic factors and inflammatory factors, suggesting that the wnt signaling represents a new therapeutic target for these ocular diseases. The purpose of this study is to evaluate the effect of a blocking antibody for LRP6, a co-receptor of the wnt pathway, on the wnt signaling in the retina and retinopathy.
A monoclonal antibody (mAb) specific for the wnt binding domain of LRP6 was generated using a recombinant LRP6 peptide. Wnt signaling was induced by wnt3a conditioned media or hypoxia in cultured retinalcell lines, including retinal pigment epithelial cells (RPEs), Muller cells, and retinal capillary endothelial cells (RCECs). The canonical wnt signaling activity and expression of pro-angiogenic, inflammatory cytokines were measured by TOP FLASH promoter activity assay, Western blotting, and ELISA. In vivo, the mAb was injected into the vitreous of a rat model with oxygen-induced retinopathy (OIR), and its effects were evaluated by Western blotting and retinal vascular permeability assay.
The mAb showed a high specificity and affinity to LRP6. In the cultured retinal cells, the mAb inhibited LRP6 phosphorylation and beta-catenin accumulation and down-regulated the expression of VEGF, ICAM-1, and CTGF induced by wnt3a and by hypoxia. However, the mAb did not inhibit LiCl-induced wnt signaling, confirming that the mAb functions via blocking the receptor-ligand interactions on the plasma membrane. In OIR rats, intravitreal injection of the mAb resulted in significant reduction of beta-catenin levels and down-regulation of VEGF expression in the retina, suggesting that the mAb inhibits the canonical wnt pathway induced by ischemia. Moreover, injection of the mAb also significantly reduced vascular permeability in the OIR model.
The mAb specific for the LRP6 ectodomain suppresses wnt signaling activation and inflammatory cytokine expression, demonstrating therapeutic potential for AMD and diabetic retinopathy.
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