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Colin Andrew Bretz, Eric Kunz, Thipparat Suwanmanee, Tal Kafri, M Elizabeth Hartnett; Endothelial Cell STAT3 Knockdown Inhibits Intravitreal Neovascularization in a Rat Model of Oxygen Induced Retinopathy. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5467. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies show that downstream activation of signal transducer and activator of transcription 3 (STAT3) by vascular endothelial growth factor signaling in endothelial cells (EC) is associated with intravitreal neovascularization (IVNV) in oxygen-induced retinopathy (OIR) models representative of severe retinopathy of prematurity (ROP). Pharmacologic inhibition of STAT3 has been shown to mediate vascular pathology in OIR, however innate STAT3 is necessary to clear methicillin resistant S. aureus pneumonia, a common condition in premature infants, making broad STAT3 inhibition problematic as a potential therapeutic. We tested the hypothesis that knockdown of STAT3 specifically in ECs would reduce IVNV.
Within 4-6 hours of birth, litters of Sprague Dawley rats (12-16 pups) were placed into an Oxycycler and exposed to alternating 24 hour periods of 50% and 10% oxygen for 14 days. On postnatal-day (P)8, rat pups received bilateral 1ul subretinal injections of either CDH5-driven STAT3 shRNA or CDH5-driven luciferase shRNA lentiviruses. Pups were moved to room air at P14 and sacrificed P20. Retinal flatmounts were stained with isolectin-B4 to visualize vasculature and captured by confocal microscopy. Images were analyzed in ImageJ to determine the avascular area (AVA) and IVNV relative to total retinal area. Results were analyzed using a mixed regression model to account for intralitter and between-eye clustering. Data were reported as means ± SEM with p < 0.05 as statistically significant with each condition having ≥ 25 flatmounts.
Analysis of retinal flat mounts at P20 revealed that AVA was not significantly different between STAT3 shRNA (39.75% ±2.12%) and luciferase shRNA (39.15% ±2.35%). However, IVNV was reduced 35% in STAT3 shRNA flatmounts compared to luciferase shRNA (STAT3 shRNA 2.05% ±0.32% vs. Luciferase shRNA 3.18% ±0.34; p<0.001).
EC-specific knockdown of STAT3 inhibits IVNV without altering AVA. This suggests that targeting EC-STAT3 may be an effective way to inhibit IVNV, while avoiding the known issues of more broad inhibitors.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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