Intravitreal pro-inflammatory cytokines induce signs of diabetic retinopathy in non-obese diabetic mice

Abstract

Purpose : A key limitation to research in diabetic retinopathy (DR) is that most animal models are hyperglycaemia-only models that do not account for the role of inflammation in the development of the disease. As both inflammation and hyperglycaemia cause the pathological events in the clinical condition, this study determined whether inflammation introduced exogenously in diabetic mice can induce signs of DR in a similar pattern to the human condition.

Methods : IL-1β and TNF-α (cytokine group) or saline (control group) were intravitreally injected into both eyes of female, 15-week old, CD1 (normoglycemic) and NOD (hyperglycemic) mice. Three mice/strain received intravitreal saline while six mice/strain were administered intravitreal cytokine injection. Fundus and OCT images were obtained before (day 0) as well as on days 2 and 7 after intravitreal cytokine injection. Vessel dilation and beading which are signs of vascular damage in DR were assessed from fundus images. Retinal and vitreous hyper-reflective foci (HRF) as well as retinal thickness were graded on OCT images. Eyes were enucleated on day 7 and immunohistochemistry was performed to assess glial fibrillary acidic protein (GFAP) and Iba1 expression as a marker of astrogliosis and microgliosis respectively.

Results : Fundus images revealed that pro-inflammatory cytokines induced vessel dilation and beading in NOD but not CD1 mice. OCT images showed that the cytokines induced appearance of vitreous HRF in both mouse strains but worse in NOD than in CD1 mice on days 2 and 7 (p < 0.0001 for both). Furthermore, retinal HRF did not occur in CD1 but could be seen on day 2 in NOD mice following intravitreal cytokine injection. About 90% of retinal HRF evolved into retinal oedema in cytokine-treated NOD mice by day 7. Immunohistochemical analyses for GFAP and Iba1 revealed increased astrogliosis as well as microglia activation in the outer nuclear layer in cytokine-treated NOD compared to saline-treated NOD and cytokine-treated CD1 mice.

Conclusions : The present study provides evidence for a significant role of the concerted action of hyperglycaemia and inflammation in DR as well as an understanding of the role of inflammation in the development of the disease.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.