Effects of arteriolar constriction on retinal gene expression and Müller cell responses in a rat model of branch retinal vein occlusion.

BACKGROUND: To investigate the effect of induced arteriolar constriction (AC) on alterations in gene expression of factors implicated in the development of edema in branch retinal vein occlusion (BRVO). METHODS: In Brown-Norway rats, BRVO was induced by laser photocoagulation of the veins in one half of the retina. AC of the afferent arterioles was performed 30 min later. We then determined the expression of Vegfa, Vegfb, Pedf, Kir4.1, Aqp4, Aqp1, Il1ß, and Il6 with real-time polymerase chain reaction (RT-PCR) in the neuroretina and retinal pigment epithelium (RPE) after 1, 3, and 7 days. Immunostaining against GFAP, aquaporin (AQP)-4, and Kir4.1 was performed on days 1 and 3. RESULTS: BRVO resulted in transient upregulation of Vegfa in the neuroretina on day 1. The expressions of Kir4.1, AQP4, and AQP1 were downregulated, and Il1ß and Il6 were strongly upregulated, on days 1 and 3. The retinal distribution of GFAP and AQP4 proteins remained unaltered, while the Kir4.1 protein displayed redistribution from polarized to uniform retinal distribution. AC accelerated the restoration of downregulated Kir4.1, Aqp4, and Aqp1 in the RPE, of Kir4.1 in the neuroretina, and of upregulated Il6 in the neuroretina. AC did not influence the gliotic alterations of Müller cells and the redistribution of the Kir4.1 protein. CONCLUSION: Constriction of the afferent artery in the BRVO region accelerated the restoration of potassium channels and Il6. These alterations may contribute to faster resorption of retinal edema, and may decrease the level of inflammation.

Effect of intravitreal anti-vascular endothelial growth factor treatment on the retinal gene expression in acute experimental central retinal vein occlusion.

PURPOSE: To determine the effect of intravitreal bevacizumab and anti-vascular endothelial growth factor (VEGF) antibodies on the gene expression in the neural retina in a rat model of central retinal vein occlusion (CRVO). METHODS: The CRVO was induced by laser photocoagulation of all retinal veins. The animals were divided into 3 groups (in each, n = 16): group CRVO only without any further treatment, group CRVO with bevacizumab, and group CRVO with anti-VEGF antibodies. The intravitreal injection of bevacizumab or anti-VEGF antibodies was performed 15 min after CRVO induction. The left eyes in all animals served as untreated controls. The expression of factors which influence the development of vascular edema (VEGF-A, pigment epithelium-derived factor, PEDF), of channels implicated in retinal osmohomeostasis (Kir4.1, AQP4, AQP1) and of the proinflammatory cytokines interleukin (IL)-1ß and IL-6 was determined by using real-time RT-PCR after 1 and 3 days of CRVO. RESULTS: CRVO induced a rapid transient upregulation of Vegfa after 1 day, and a delayed upregulation of Pedf after 3 days of CRVO. The expression levels of Kir4.1, Aqp4 and Aqp1 were strongly decreased, and the levels of Il1ß and Il6 were strikingly increased after CRVO. Intravitreal bevacizumab and anti-VEGF antibodies fully prevented the upregulation of Vegfa after 1 day, and the upregulation of Pedf after 3 days of CRVO, and decreased the upregulation of Il1ß after 1 day of CRVO. Anti-VEGF treatment had no effect on the expression levels of Kir4.1, Aqp4, Aqp1, and Il6. CONCLUSIONS: It is suggested that the inhibitory effect on the upregulation of Vegfa and Il1ß contributes to the edema-resolving effect of anti-VEGF treatment.

Effects of intravitreal triamcinolone acetonide on retinal gene expression in a rat model of central retinal vein occlusion.

PURPOSE: The aim of this study was to investigate the effects of intravitreal triamcinolone acetonide on the alterations in retinal gene expression in a rat model of central retinal vein occlusion (CRVO). METHODS: In one eye of adult Brown Norway rats (n = 77) CRVO was induced with laser photocoagulation of all retinal veins near to the optic disk after intraperitoneal injection of 0.2 ml of 10% sodium fluorescein. The gene expression was investigated using RT-PCR separately in the neural retina and retinal pigment epithelium (RPE) 1, 3, 7, and 14 days after CRVO induction. We analyzed the expression of factors that influence the development of vascular edema (VEGF-A, VEGF-B, PEDF), of channels implicated in retinal osmohomeostasis (Kir4.1, AQP4, AQP1), and of the pro-inflammatory factors IL-1ß and IL-6. RESULTS: CRVO induced a rapid transient upregulation of Vegfa, a downregulation of Vegfb, and a delayed upregulation of Pedf in the neuroretina. In the neuroretina and retinal pigment epithelium, CRVO induced strong, transient downregulation of Kir4.1, Aqp4, and Aqp1, and striking rapid upregulation of Il1ß and Il6. Intravitreal triamcinolone reversed the downregulation of Kir4.1 and accelerated the normalization of the upregulated expression of Il1ß and Il6. The CRVO-induced transient upregulation of Vegfa was not influenced by the triamcinolone application. CONCLUSIONS: Triamcinolone exerts anti-inflammatory effects in the ischemic retina by inhibitory effects on the gene expression of IL-1ß and IL-6, and may have neuroprotective effects via improvement of retinal potassium homeostasis.