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Maria Vähätupa, Giulia De Rossi, Tero AH Järvinen, Hannele Uusitalo-Järvinen, James R Whiteford; Sdc4 deficiency leads to reduced VEGFA induced pathological ocular angiogenesis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5474.
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© ARVO (1962-2015); The Authors (2016-present)
Syndecan-4 (Sdc4) is a heparan sulfate proteoglycan (HSPG) mediating cell migration, adhesion and proliferation. VEGF and VEGF receptors (VEGFR2) have been shown to bind to HSPG. Since VEGF/VEGFR2-axis is important for angiogenesis, we tested the hypothesis that Sdc4 could have role in ocular angiogenesis, using oxygen-induced retinopathy (OIR) model.
The expression of Sdc-family members 1-4 was studied with qPCR from P0, P4, P7, P12 and P17 retinas during development and OIR. Revascularization and neovascularization (NV) were quantified at P17 OIR. Neovascular membranes obtained from patients with PDR were stained with anti-Sdc4, -CD31 and -VEGFR2 antibodies and their expression levels was quantified. To study the responsiveness to VEGFA, WT and Sdc4-/- mice were injected with Matrigel containing VEGF and/or bFGF and the plug vascularity was analyzed. VEGFR2 dependent signaling was studied by examining VE-Cadherin internalization in WT and Sdc4-/- MLECs after VEGFA stimulation. Retinal sections from Sdc4-/- and WT mice were stained for GS-IB4 and VE-Cadherin.
Sdc4 expression remained constant during vascular development in retina, but peaked in the OIR at P17 (2.5±0.9 fold, p<0.01, n=5-6/group). In OIR, Sdc4-/- retinas had slightly increased physiological angiogenesis, but had less NV (2.4±1.7%/retinal area) than WT (4.3±2.3 %/retinal area, p<0.001, n=42/34 retinas). The expression of Sdc4 correlated with VEGFR2 expression in the PDR membranes (r=0.751, p<0.05, n=6 samples). Matrigel plugs revealed that Sdc4-/- tissues fail to respond to VEGF (plug vascularity 0.0093±0.0086 HG mg/ml/g) (but not to bFGF), while WT tissues responded to both (VEGF plug vascularity 0.048±0.028 HG mg/ml/g, p<0.05, n=9/group). We found impaired VE-Cadherin internalization in Sdc4-/- MLECs (6.4±4.9 puncti/cell) compared to WT (34.6±12.6 puncti/cell, p<0.0001, n=3, 5 images/group) after VEGFA stimulation and less disrupted VE-Cadherin expression in Sdc4-/- vasculature in OIR.
Our results show that Sdc4 expression is induced in OIR during pathological angiogenesis, but not during vascular development. There is reduced NV in Sdc4-/- mice compared to WT in OIR and Sdc4 expression correlates with VEGFR2 expression on PDR membranes. We also show that Sdc4 is crucial for the VEGFA induced angiogenesis in injected matrigel plugs. Our results suggest that Sdc4 is needed for VEGFA/VEGFR2 mediated angiogenesis.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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