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Xiang Ma, Rui Cheng, Yusuke Takahashi, Jian-Xing (Jay) Ma; Dysregulation of Wnt signaling promotes the sub-retinal fibrosis in neovascular age-related macular degeneration (nAMD). Invest. Ophthalmol. Vis. Sci. 2020;61(7):3682.
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© ARVO (1962-2015); The Authors (2016-present)
Sub-retinal fibrosis is a key pathological feature in nAMD leading to irreversible vision loss. The aberrant activation of canonical Wnt signaling is associated with neovascularization in nAMD patients and the laser-induced choroidal neovascularization (CNV) model. Previously, we showed that the soluble extracellular domain of very low-density lipoprotein receptor (sVLDLR) exerts the potent inhibitory effect on Wnt signaling. This study aims to investigate if the level of sVLDLR is reduced in the retina, which may result in over-activation of Wnt signaling, contributing to the sub-retinal fibrosis in nAMD.
The sVLDLR level in the interphotoreceptor matrix (IPM) of the CNV model was measured by Western blot analysis. In Vldlr-/- mice, fibrosis markers were measured by immunostaining and ELISA. primary human retinal pigment epithelial (RPE) cells and primary mouse RPE cells isolated from Vldlr-/- mice were used in this study. Following the treatment of TGFβ2 and Wnt3a conditioned medium (WCM), fibrosis markers were evaluated in these primary RPE cells. To evaluate the anti-fibrotic effect of sVLDLR, the primary RPE cells were pre-treated with sVLDLR conditioned medium (VCM). Similarly, the anti-fibrotic effect of 2F1, a monoclonal antibody blocking Wnt co-receptor LRP6, was also measured.
There was a significant reduction of the sVLDLR level in mice with laser-induced CNV. Immunostaining detected the expression of α-smooth muscle actin (α-SMA) in the RPE of Vldlr-/- mice. Fibronectin was upregulated in the RPE-choroid complex of Vldlr-/- mice. In human RPE cells, WCM showed the synergistic effect with TGFβ2 on the induction of α-SMA and connective tissue growth factor (CTGF) expression. Vldlr knockdown in human RPE cells and Vldlr knockout in mouse RPE cells enhanced TGFβ2-induced α-SMA and CTGF over-expression. VCM reversed the fibrosis factor expression induced by WCM. Blockade of Wnt signaling by 2F1 suppressed the pro-fibrotic effect of Vldlr KO in primary RPE cells.
Reduced sVLDLR level in the IPM of the CNV model contributes to the over-activation of Wnt signaling and fibrosis. Wnt signaling activation promotes TGFβ2-induced sub-retinal fibrosis. sVLDLR confers an anti-fibrotic effect through inhibition of Wnt signaling and thus, may provide a therapeutic target for sub-retinal fibrosis in nAMD.
This is a 2020 ARVO Annual Meeting abstract.
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