Suppression of Retinal Neovascularization by Erythropoietin siRNA in a Mouse Model of Proliferative Retinopathy

Abstract

Purpose Erythropoietin (EPO), an oxygen-regulated hormone stimulating erythrocyte production, was recently found to be critical for retinal angiogenesis. EPO mRNA expression levels in retina are highly elevated during the hypoxia-induced proliferation phase of retinopathy. The authors investigated the inhibition of retinal EPO mRNA expression with RNA interference as a potential strategy to suppress retinal neovascularization and to prevent proliferative retinopathy. Methods The authors used a mouse model of oxygen-induced retinopathy. Retinal EPO and Epo receptor (EpoR) expression during retinopathy development were quantified with real-time RT-PCR in whole retina and on laser-captured retinal vessels and neuronal layers. Retinal hypoxia was assessed with an oxygen-sensitive hypoxyprobe. A small interference RNA (siRNA) targeting EPO or control negative siRNA was injected intravitreally at postnatal (P) day 12, P14, and P15 during the hypoxic phase, and the effect on neovascularization was evaluated in retinal flatmounts at P17. Results Retinal EPO mRNA expression in total retina was suppressed during the initial phase of vessel loss in retinopathy and was significantly elevated during the hypoxia-induced proliferative phase in all three neuronal layers in the retina, corresponding to an increased level of retinal hypoxia. EpoR mRNA expression levels also increased during the second neovascular phase, specifically in hypoxia-induced neovascular vessels. Intravitreous injection of EPO siRNA effectively inhibited approximately 60% of retinal EPO mRNA expression and significantly suppressed retinal neovascularization by approximately 40%. Conclusions Inhibiting EPO mRNA expression with siRNA is effective in suppressing retinal neovascularization, suggesting EPO siRNA is a potentially useful pharmaceutical intervention for treating proliferative retinopathy.

Antiangiogenic Therapy for Ischemic Retinopathies

“…This study provided the first evidence that EPO acts on the angiogenic pathway independently from VEGF and is more strongly correlated with the presence of PDR than VEGF (Watanabe et al 2005). Subsequent studies have shown genetic mutations can increase EPO expression and this is associated with increased risk of PDR and related condition in patients and in animals (Tong et al 2008;Chen et al 2009;Xiong et al 2009;Abhary et al 2010).…”

Endothelial microRNA-150 is an intrinsic suppressor of pathologic ocular neovascularization

“…Intravitreal injections were performed following established protocols (49,50). We injected 1 μg of miR-150 mimics (Ambion) using a 33-gauge needle behind the limbus of the eye, and the contralateral eye of the same animal was injected with an equal amount of negative control mimics.…”

Exogenous erythropoietin aggravates retinal neovascularizationin a murine model of proliferative retinopathy

“…Endogenous EPO in the retina is crucial for retinal angiogenesis (10,20). A previous study showed that mRNA expression of EPO is increased greatly in the second phase of retinopathy (12). After intravitreal injection of small interference RNA (siRNA), expressions of EPO as well as RNV are significantly suppressed through RNA interference.…”

“…On the other hand, suppression of EPO would be beneficial for the inhibition of retinal pathological vessels in the second phase (12). Intravitreal injection of small interference RNA is effective in hindering the development of RNV (12). Moreover, a recent study indicated that early EPO administration did not raise the risk of ROP (13).…”