Molecular and histological changes following central retinal artery occlusion in a mouse model q Nitza Goldenberg-Cohen a, b, c,1 , * , Shimrit Dadon c,1 , Bat-Chen R. Avraham c , Michal Kramer a, b , Murat Hasanreisoglu a, b , Ido Eldar a, b , Dov Weinberger a, b , Irit Bahar a, b a Department of Ophthalmology, Rabin Medical Center, Beilinson Campus, Petah Tiqwa, Israel b Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel c The Krieger Eye Research Laboratory, Felsenstein Medical Research Center, Petah Tiqwa, Tel Aviv University, Tel Aviv, Israel article info Article history: Received 6 November 2007 Accepted in revised form 23 June 2008 Available online 28 June 2008 Keywords: central artery occlusion CRAO mouse model molecular changes abstract The aim of this study was to characterize the molecular and histological changes that occur in the retina following central retinal artery occlusion (CRAO) in a mouse model. CRAO was induced in 60 mice by laser photoactivation of intravenously injected rose bengal. Mice were sacrificed at 3, 6, 12, and 24 h and 7 and 21 days after CRAO induction for molecular analysis (5–13 mice/time point) and histological and apoptosis studies (3–4 mice/time point). Fundus examination and fluorescein angiography were also performed at various points. Retinal mRNA was analyzed for expression of T-cell antigen 1 (Thy-1), vascular endothelial growth factor (VEGF), heme oxygenase-1 (HO-1), and hypoxia-induced factor 1a (HIF-1a) using real-time polymerase chain reaction. The results showed that at 6–24 h following CRAO induction, the retina was edematous, with interrupted blood perfusion. Fluorescein angiography showed reperfusion at 6 h, and TdT-mediated dUTP nick end-labeling (TUNEL) assay revealed an increase in apoptotic cells in the first 24 h. On histological sections, nuclear loss in the inner retinal layers was maximal on day 21. Thy-1 expression decreased to 30% of baseline (P  0.002). VEGF expression increased in the first 3 h and gradually decreased thereafter, reaching 75% of baseline on day 21 (P  0.005). HO-1 was upregulated at all time points, with a peak at 12 h. No change was noted in HIF-1a expression at any time. In conclusion, CRAO in mice causes cell apoptosis in the inner layers of the retina, with a significant cell loss and a decrease in Thy-1 expression by 21 days. These changes are accompanied by a rise in expression of the ischemia-related protein HO-1 to a peak at 12 h, with levels remaining above control values at day 21. Given the similarity of the mouse model to human CRAO, these findings may have implications for the future clinical management of CRAO. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Central retinal artery occlusion (CRAO) accounts for 1 per 10,000 outpatient visits in the United States (Sharma, 2001; Yuzurihara and Iijima, 2004). It is considered an ophthalmologic emergency because of the high risk of severe visual loss; only 21–35% of af- fected eyes retain useful vision (Sharma, 2001; Yuzurihara and Iijima, 2004). Even when treatment is provided early, most patients show irreversible injury to the retina followed by optic atrophy (Sharma, 2001; Yuzurihara and Iijima, 2004). Several animal models of CRAO have been developed to in- vestigate the pathogenesis of the disorder and the effect of treat- ment (Daugeliene et al., 2000; Hayreh and Jonas, 2000; Hayreh et al., 2004; Iliaki et al., 1996; Jonas and Hayreh, 1999; Zhang et al., 2005). Hayreh and colleagues (Hayreh and Jonas, 2000; Hayreh et al., 2004; Jonas and Hayreh, 1999) clamped the central retinal artery in the retrobulbar space of rhesus monkeys and found that the duration of occlusion (<100 min vs. >240 min) was directly related to the degree of optic nerve atrophy and nerve fiber loss. Iliaki et al. (1996) and Daugeliene et al. (2000) exposed rabbit and rat eyes, respectively, to laser treatment following injection of photosensitive dyes. The oxygen released by the dyes caused vas- cular endothelium injury, platelet activation, and subsequent for- mation of an intraluminal thrombus in the irradiated area of the blood vessel (Daugeliene et al., 2000; Iliaki et al., 1996). Recently, q This study was partially supported by the Zanvyl and Isabelle Krieger Fund, Baltimore, Maryland, USA and the Young Investigator Fund (I.B.), Rabin Medical Center, Petah Tiqwa, Israel. This work was presented in part at the annual meeting of the Israel Society for Eye and Vision Research, Neve-Ilan, Israel, March 2006. * Corresponding author. Department of Ophthalmology, Rabin Medical Center, Beilinson Campus, Petah Tiqwa 49100, Israel. Tel.: þ972 3 937 6101; fax: þ972 3 921 9084. E-mail address: ncohen1@gmail.com (N. Goldenberg-Cohen). 1 Dr. Goldenberg-Cohen and Ms. Dadon contributed equally to this study. Contents lists available at ScienceDirect Experimental Eye Research journal homepage: www.elsevier.com/locate/yexer 0014-4835/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.exer.2008.06.014 Experimental Eye Research 87 (2008) 327–333