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Patricia A D'Amore, Cindy Park-Windhol, Yin Shan Eric Ng, Jinling Yang, Vincent Primo, Magali Saint-Geniez; Endomucin inhibits VEGF-induced endothelial cell migration, growth, and morphogenesis by suppressing VEGFR2 signaling. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3637. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Angiogenesis is central to both normal and pathologic processes. Endomucin-1 (EMCN) is a type I O-glycosylated, sialic-rich glycoprotein, specifically expressed by venous and capillary endothelium but its possible role in vascular development is unclear. We examined the role of EMCN in angiogenesis using in vivo and in vitro models.
C57BL/6J mice were injected intravitreally with siEMCN or scrambled siRNA (siCtrl) at postnatal day four (P4). The effect of EMCN knockdown on vascular development in P6 retinas was evaluated for vascular radial expansion, vessel density, branch point, and filopodia number. Gain- and loss-of-function studies were performed in human retinal endothelial cells (HREC) examining migration in a wound-healing assay, proliferation by cell counting, tube morphogenesis in a collagen gel with levels of cellular kinase activity measured by immunoblot.
EMCN knockdown led to impaired retinal vascular development in vivo. Compared to siCtrl-injected mice, siEMCN-injected P6 mice showed a delay in radial expansion of the developing mouse vasculature (51±2% vs. 69±2%, P<0.0001), reduced vessel density (49±2% vs. 66±5%, P<0.01), decreased number of branch points per μm2 (43±1 vs. 64±4, P<0.0001), and reduced number of filopodia per 100 μm (18±1 vs. 28± 2, P<0.05). HRECs transfected with siEMCN had reduced migration (22±1% vs. 59±3%, P<0.0001), proliferation (15100±125 cell/cm2 vs. 22500±1500 cell/cm2, P<0.05), and tube morphogenesis (total tube length in μm; 7201±86 vs. 9157±273, P<0.005), whereas EMCN over-expression led to an increase in migration (75±4% vs. 53±6%, P<0.05), proliferation (33500±596 cell/cm2 vs. 26100±782 cell/cm2, P<0.05) and tube morphogenesis (11164±497 μm vs. 8311±373.0 μm, P<0.05). Knockdown of EMCN suppressed VEGF-induced signaling: decreased phospho-VEGFR2, phospho-ERK1/2, and phospho-p38-MAPK levels.
Reduction of EMCN expression using siRNA reduced HREC migration, proliferation, and tube morphogenesis in vitro and interfered with developmental angiogenesis in vivo, whereas over-expression of EMCN led to increased migration, proliferation and tube morphogenesis. These results suggest a novel role for EMCN as a potent regulator of angiogenesis and points to it potential utility as a new therapeutic target for angiogenesis-related diseases.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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