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Y. Saito, T. Nakanishi-Ueda, S. Iwai, M. Ohbayashi, T. Ueda, H. Yasuhara, K. Oguchi, R. Koide; Investigation of Mechanism in Oxygen-Induced Retinal Neovascularization of the Neonatal Rat Model. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2982.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate mechanism of rat model of oxygen-induced retinopathy (OIR).
Neonatal Sprague-Dawley rats were exposed to daily cycles of 80% oxygen (20.5 h), ambient air (0.5 h), and progressive return to 80% oxygen (3 h) until postnatal day 12 (P12) (Phase I), then the rats were placed in ambient air until P18 (Phase II). Rat pups in room air (RA) were used as controls. On P4, P8, P12, P13, and P18, the retinas were fixed for flat mounts or collected for RT-PCR and western blot analyses. Flat mounted retinas were stained with ADPase and retinal avascular areas (AVAs) were measured as a % of total retinal area (%AVAs) using Image J (NIH). mRNA of VEGF-A, VEGFR-1, VEGFR-2, HIF-1alpha, MMP-2, MMP-9 and caspase-3 were measured by RT-PCR . The levels of mRNA were calculated at P18 OIR as 100%. Cleaved caspase-3 was measured by western blot . Statistical analyses were performed by ANOVA and student t-test.
%AVAs of OIR and RA were gradually decreased after birth significantly (p<0.0005). At P8, mRNA of MMP-2, caspase-3 and HIF-1alpha increased to 386%, 184% and 168% respectively. At P13, mRNA of MMP-9, VEGF-A and VEGFR-1 increased to 145%, 128% and 116% respectively. In RA, cleaved caspase-3 decreased significantly at P18 (p<0.005), compared at P4 and P8, but not decreased in OIR (p=0.28). There was significant difference in cleaved caspase-3 between OIR and RA at P18 (p<0.05).
It is considered MMP-2 and caspase-3 contribute to Phase I, and MMP-9 and VEGF-A contribute to Phase II. On the other side, cleaved caspase-3 did not decrease in OIR retina, considering apoptosis remains through Phase I to II. Cleaved caspase-3 in early phase of RA is considered as physiological apoptosis. Limitation of this study is that it is not clear which cells in retina had apoptosis. Apoptotic cells in Phase I may be different from the cells in Phase II. Further study is warranted.
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