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Kenneth P Mitton, Roberto Schunemann, Eduardo Guzman, Wendy Dailey, Mei Cheng, Kimberly A Drenser, Michael Thomas Trese; In Vivo Model of the Molecular, Functional, and Morphological Changes Occurring During Blood Retinal Barrier Disruption by VEGF. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2690.
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VEGF-related signal transduction and gene regulatory networks play central roles in the vascular pathology of several retinal diseases: ROP, diabetic retinopathy, AMD, Norrie’s disease and FEVR. While mechanisms are often explored in cell culture, there is need for in vivo models that are amenable to functional and molecular analysis during blood-retinal barrier (BRB) disruption and inflammatory response. We developed an intravitreal VEGF-injection model that provides a new platform for functional assessment of BRB disruption and countermeasures using ERG, Fluorescein angiography (FA) and Optical Coherence Tomography (OCT) in a single session of anesthesia.
Retinas of Long Evans rats were documented with bright-field imaging, FA, & OCT. Some animals received ERG, FA and OCT during a single session in an advanced ocular imaging suite of the Pediatric Retinal Research Laboratory. Subsequently, rats received a single intravitreal injection of recombinant human VEGF (35-gage microsyringe), completed under a surgical microscope. Imaging and ERG analysis were repeated as early as 24 hrs post-injection. Retinas were also processed for histology or RNA extracted for gene expression analysis.
Documenting the retinal vasculature before and after VEGF injection revealed a VEGF-induced dilation of the primary retinal veins by 24 hrs. Vascular dilation resolved over several days. Icam1 and Tnfa gene expression increased significantly (20x and 10x respectively) during vessel dilation. Cldn5 (Claudin-5) gene expression was reduced by 75%, confirming an acute disruption of endothelial cell-cell junctions. Following the same eye, sub-retinal fluid accumulation was seen by OCT as vessel dilation resolved. Accumulated sub-retinal fluid resolved over one week.
A model of BRB disruption by VEGF was developed using a pigmented rat strain. Our advanced ocular imaging & ERG suite provides a powerful model to explore the mechanisms of VEGF receptor activation and BRB disruption in vivo. Monitoring the same eye with fundus imaging, FA, OCT and ERG at several time points follows BRB disruption through to its resolution. Combined with gene expression analysis, the model provides a platform to evaluate countermeasures of BRB disruption, inflammatory response, and it is useful for evaluation of intra-ocular toxicity.
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