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Wei-Kang wu, Lindsay B. Nicholson, Andrew D. Dick; Il-4 Conditions Macrophage In Vitro and Retina In Vivo to Generate Soluble Flt-1 Expression and Inhibit Laser-induced CNV in Mice. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6903.
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During both Retinal and choroidal angiogenesis activation and infiltration of myeloid derived cells occurs. The exact role myeloid derived cells play in pathological angiogenesis remains undefined. We have found that IL-4-conditioned murine macrophages display anti-angiogenic properties, notably increasing soluble Flt-1 secretion in vitro. To interrogate whether as a consequence there exists a potential therapeutic translational role for IL-4 to inhibit angiogenesis, IL-4was administered intravitreally during laser-induced choroidal neovascularization (CNV).
Bone marrow derived macrophages (BMDMs) were conditioned with IL-4 (20U/ml), and both sFlt-1 mRNA and protein expression were determined. HUVEC activity was assessed by alamarBlue to determine the bioactivity of sFlt-1 in supernatants of IL-4 conditioned BMDM, whilst specificity of sFlt-1 activity was confirmed following treatment with sFlt-1 siRNA. To determine whether intravitreal administration of IL-4 inhibited angiogenesis in C57BL/6 mice, CNV was induced by laser treatment. The choroidal and retinal tissue was also examined for macrophage infiltration and sFlt-1 mRNA expression.
IL-4 treatment induced macrophage sFlt-1 expression. Conditioned media from these macrophages inhibited HUVEC activity, and the effect was reversed in IL-4 treated sFlt-1 siRNA knockdown macrophages. In vivo we confirmed CD11b+ macrophage retinal infiltration during the development of CNV. Giving IL-4 intravitreally decreased angiogenesis and upregulated retinal sFlt-1, arginase-1 and YM1 gene expression compared to normal retina following IL-4 administration.
We have shown that IL-4 induced macrophage sFlt-1 which in turn significantly decreased endothelial cell proliferation in vitro. IL-4 administration inhibited angiogenesis in laser-induced CNV. IL-4-mediated sFlt-1 production was observed in laser-treated but not in naïve retina, inferring that pro-angiogenic activation is critical for the sFlt-1-mediated IL-4 inhibitory response. Taken together, our study supports the therapeutic potential of IL-4 to suppress pathological angiogenesis via induction of sFlt-1 from macrophages.
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