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A. Uppal, Y. Saito, D. K. Sutton, P. Geisen, G. Cui, L. J. Peterson, M. E. Hartnett; Effects of Supplemental Oxygen Treatment on Oxygen-Induced Retinopathy in Neonatal Rats. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3410.
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To investigate the effects of supplemental oxygen treatment on oxygen-induced retinopathy (OIR) in neonatal rats.
We used a 50/10 OIR model that exposes Sprague-Dawley newborn rat pups to repeated cycles of 24 h of 50% oxygen alternating with 24 h of 10% oxygen until postnatal 14 days (p14). Afterwards, some of the litters were exposed to supplemental oxygen (28% O2, SO model) until p20 and the others were moved to room air (OIR model). Pups were injected with Pimonidazole (Hypoxyprobe: HP) 90 minutes before sacrifice and retinal dissection. Half of the retinas were fixed for flatmounts or cryosections, while the rest were collected for western blot analysis. Flat mounts and cryosections of retinas were stained with Griffonia simplicifoliaisolectin and HP antibody. The flat mounts were scored for intravitreous neovascularization (IVNV) by counting clock hours and for avascular areas as a percent of total retinal area (%AVA) using Image J (NIH). HP level in retinal tissue was measured by Western blot. Data was analyzed by Mann-Whitney U-test and ANOVA using SPSS software.
HP was significantly increased at p18 vs. p13 and p17 vs p13 in the OIR model (one-way ANOVA p=0.002 & Bonferroni p<0.05), and HP was observed to localize specifically within the ganglion cell layer to outer nuclear layer of peripheral avascular retina in flatmounts and cryosections. There was no significant difference between SO model and OIR model at p20 in clock hours IVNV (SO: 3.7±1.0 S.E., OIR: 4.2±0.6) nor %AVA (SO: 7.30%±1.24, OIR: 9.26%±1.63). In addition, there was no significant difference in HP levels between the SO model and OIR model retinas at p20.
Supplemental oxygen might not be useful for reducing tissue hypoxia, neovascularization or peripheral avascularity following oxygen-induced retinopathy. However, further study is required to confirm this result. Hypoxyprobe proved to be a useful tool for locating and quantitatively measuring hypoxic areas of the retina.
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