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Brahim Chaqour, Maria B Grant, Lulu Yan, Sangmi Lee; MicroRNA-155-dependent regulation of the matricellular protein CCN1 modulates neovascular growth in the retina. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):42.
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MicroRNA-dependent control of angiogenic growth factor expression plays an important role in the pathogenesis of retinal neovascularization (RNV), which occurs as a result of progressive vasoobliteration and compensatory aberrant neovascularization of the eye. This study examined the role of miR-155 in the regulation and function of CCN1, a highly angiogenic heparin- and integrin-binding extracellular matrix protein, expressed in the retinal vasculature during development and under ischemic conditions.
Mice with constitutive and inducible deletion of miR-155 and CCN1 respectively were used in this study. Quantification of miRNAs was done by qPCR and retinal vascular phenotype was determined by immunohistochemistery in mouse pups left untreated or subjected to oxygen-induced retinopathy (OIR) i.e., exposure to 75% oxygen for 5 days at postnatal day 7 followed by normoxia for 5 days. Two-tailed Student’s t-test was used for statistical analysis..
Micro-RNA-155 is minimally expressed in the retina during postnatal development of the vasculature. However, exposure of wild-type mice to OIR significantly increased miR-155 levels in the retina. Similarly, while ubiquitous deletion of miR-155 in mice resulted in minor overt retinal vascular defects during development, miR-155-deficiency was associated with rapid revascularization and/or normalization of the retinal vasculature following exposure to OIR injury. Expression of miR-155 was inversely correlated to that of CCN1, a secreted cysteine-rich protein required for proper cardiovascular development and embryonic viability. Conditional inactivation of the CCN1 gene in mice caused retinal vascular malformations typical of faulty maturation and mimicked the vascular phenotype associated with miR-155-gain-of function during development. In wild-type OIR mice, ectopic expression of CCN1 was sufficient to suppress neovascular growth. Mechanistically, miR-155-induced loss of CCN1 function alters resident microglial populations that are responsible for the formation of organized retinal vascular network.
Micro-RNA-155-dependent downregulation of the CCN1 gene induces abnormal vessel growth in the OIR model. Targeting miR-155 could present a potential therapeutic tool for treatment of pathological RNV.
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