Abstract
Purpose :
Neovascularization is the vision-threatening vascular pathology that develops in diabetic retinopathy (DR) and retinopathy of prematurity (ROP). This pathological process is primarily driven by angiogenic factors such as vascular endothelial growth factor (VEGF), which cause retinal vessels to become proliferative and leaky. Inflammation drives the development of neovascularization and features the activation of retinal microglia, resident immune cells of the retina. However, circulating immune cells, such as leukocytes and lymphocytes, can enter the retina due to breakdown of the blood-retinal barrier, further exacerbating inflammation. Neutrophils are the most abundant type of leukocytes and are found in the vitreous of DR patients, but their role in neovascularization is largely unknown.
Methods :
Two robust models of retinal inflammation and vasculopathy were studied: oxygen-induced retinopathy (OIR) and streptozotocin (STZ) type-1 diabetes. OIR was induced by exposing C57BL6/J mice at postnatal day (P) 7 to 75% oxygen for 5 days and then room air (21% oxygen) until P18. Comparisons were made to mice housed in room air. A neutrophil depletion antibody (anti-Ly6G, 100μg) was given via IP injection every 3 days from P7, and controls received an isotype antibody. To induce DR, 6-7 week old C57BL6/J mice were administered STZ and studied for 26 weeks. Comparisons were made to non-diabetic mice administered vehicle. Twelve to 24 animals were studied per group, and data analyzed by unpaired t-tests or one-way ANOVAs. Statistical significance was defined as p<0.05.
Results :
Neutrophils (flow cytometry, CD45+CD11b+Ly6G+) increased in the blood and lymphoid organs of OIR mice from P9 to P18, and in DR mice at 13 and 26 weeks post-STZ, coinciding with the presence of retinal inflammation and vasculopathy. In OIR, the depletion of neutrophils reduced retinal vasculopathy including neovascularization, vascular leakage and VEGF levels compared to controls. In OIR, depletion of neutrophils reduced the recruitment of leukocytes to the retina, suggesting that neutrophils are major contributors to retinal inflammation.
Conclusions :
Neutrophils are one of the first responders to retinal injury in OIR, and they contribute to the development of inflammation and vasculopathy including neovascularization. Drugs targeting neutrophils may be beneficial for treating and preventing leading causes of blindness, such as DR and ROP.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.