Sergio Crespo Garcia – Progress Report 5

imageProgressReport5Netrins are a family of matrix-binding proteins that function as guidance signals. Netrin-4 displays pathologic roles in tumorigenesis and
neovascularization. To answer the question whether netrin-4 acts either pro- or anti-angiogenic, angiogenesis in the retina was assessed in Ntn-4−/− mice with oxygeninduced retinopathy (OIR) and laser-induced choroidal neovascularization (CNV), mimicking hypoxiamediated neovascularization and inflammatory mediated angiogenesis. The basement membrane protein netrin-4 was found to be localised to mature retinal blood vessels. Netrin-4, but not netrin-1 mRNA expression, increased in response to relative hypoxia and recovered to normal levels at the end of blood vessel formation. No changes in the retina were found in normoxic Ntn-4−/− mice. In OIR, Ntn-4−/− mice initially displayed larger avascular areas which recovered faster to revascularization. Ganzfeld electroretinography showed faster recovery of retinal function in Ntn-4−/− mice. Expression of netrin receptors, Unc5H2 and DCC, was found in Müller cells and astrocytes. Laser-induced neovascularization in Nnt-4−/− mice did not differ to that in the controls. Our results indicate a role for netrin-4 as an angiogenesis modulating factor in O2-dependent vascular homeostasis while being less important during normal retinal developmental angiogenesis or during inflammatory neovascularization.

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