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L. Pham, C.K. Chan, C. Spee, S.J. Ryan, D.R. Hinton; Retinal Vessel Remodeling During Hyperoxia . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1874.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Vaso–obliteration plays a key role in the pathogenesis of several forms of retinal angiogenesis. The purpose of this study was to determine the expression levels of apoptotic genes in a murine model of hyperoxia–induced retinal vaso–obliteration. Methods: To induce vessel regression, C57BL/6J neonatal mice (p7) were exposed to 75% oxygen for 5 days. The pups were euthanized, and their eyes enucleated and fixed in 4% paraformaldehyde overnight. The posterior pole of each eye was dissected and apoptosis was evaluated using a TUNEL assay. Retinas were flat–mounted and the extent of hyperoxia–induced apoptosis was visualized by confocal microscopy. To characterize gene expression during retinal vessel regression, total RNA was isolated from posterior poles of each animal subjected to the hyperoxia model at 0, 6, 12, 24, 48, 72, and 96 h. Hyperoxic regulation of caspase–3, –8, and –9, and Bcl–2 were evaluated using quantitative real–time RT–PCR. Results: The TUNEL assay revealed predominant endothelial cell–specific apoptosis in C57BL/6J mice exposed to 5 days hyperoxia. Evaluation of gene expression using real time RT–PCR showed a peak 1.4– and 2.4–fold increased expression of caspase–3 and –9 respectively following 12 h hyperoxia compared to 0 h (p < 0.01). In contrast, caspase–8 expression did not change significantly throughout the entire time course of hyperoxia. However, Bcl–2 mRNA levels became steadily elevated, reaching over 2–fold increased expression at 48 h hyperoxia compared to 0h (p < 0.0001). Conclusion: This data indicates that hyperoxia–induced vessel remodeling involves the regulation of both pro– and anti–apoptotic factors. In fact, caspase–3 and –9 may play a more important role in hyperoxia–induced vaso–obliteration compared to caspase–8. Moreover, later increased expression of Bcl–2 may be a protective response to hyperoxic insult. Further elucidation and modulation of endothelial apoptosis may provide valuable pharmacologic targets toward ischemia–induced retinopathies such as diabetic retinopathy and retinopathy of prematurity.
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