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Chiara Gerhardinger, Yang Liu, Zeina Dagher; Overexpression of IL-1 Receptor Antagonist in the Rat Retina by AAV2-mediated Gene Transfer Prevents Capillary Loss in Experimental Diabetes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5764.
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Retinal upregulation of IL-1β in diabetes has been implicated in the pathogenesis of retinopathy. The aim of this study was to test whether increasing the levels of IL-1 receptor antagonist (IL-1ra) in the retina can prevent diabetic retinopathy.
An AAV2 vector encoding human IL1ra under a CMV promoter (AAV2-hIL1ra) was injected intravitreally in the left eye of 6 weeks-old rats. The uninjected contralateral eye was used as control. Diabetes was induced by streptozotocin two weeks after intravitreal injection of AAV2-hIL1ra. Diabetic+AAV2-hIL1ra (DM+hIL1ra) rats and age-matched control rats were studied after 11 months of diabetes. The expression of hIL1ra and of rat IL-1β and ICAM1 were evaluated by qRTPCR to verify the long-term expression of the transgene and the efficacy of IL1ra overexpression to inhibit IL-1β activity. Microvascular cells apoptosis (TUNEL assay) and acellular capillaries were quantified in retinal trypsin digests to evaluate the efficacy of the gene transfer in preventing diabetes-induced retinal vascular pathology.
hIL1ra mRNA and protein were detected in all the AAV2-hIL1ra transfected retinas shortly after the gene transfer as well as after 1 year from the injection, with levels of expression 2-5 fold higher than those in human retina. The protein was also found in the vitreous indicating proper processing and secretion of transgenic hL1ra. The non-transfected retinas of DM+hIL1ra rats showed increased levels of IL1β and ICAM1 expression (p=0.015 and 0.02, respectively) as well as a significantly higher number of TUNEL+ microvascular cells (p=0.01) and acellular capillaries (p=0.03) when compared to those of control rats. Overexpression of IL1ra in transfected retinas prevented the diabetes-induced upregulation of IL1β and ICAM1 and significantly decreased the number of apoptotic cells (p=0.04 vs. non-transfected retinas). In agreement with the protection exerted by IL1ra on microvascular cell apoptosis, the number of acellular capillaries in the transfected retinas of DM+hIL1ra rats was significantly lower than in the non-transfected retinas [5 (2-9) vs. 8.5 (6-11) per mm2, median (IQR), p=0.04] and not different from that of control rats [3.5 (2-5) per mm2, p=0.6].
Chronic overexpression of IL1ra prevents excessive vascular cell death and loss of capillaries in the diabetic rat retina. The findings support a pathogenic role of IL-1β in diabetic retinopathy and propose IL1ra as a potential novel approach to prevent retinal capillary dropout in diabetes.
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