IGFBPL1 inhibits inflammation and angiogenesis through modulation of microglia activation in laser-induced choroidal neovascularization in mice

Abstract

Purpose : Intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents are recommended primary treatment for neovascular age-related macular degeneration (AMD). However, persistent fluid or recurrent exudation still occurs. The pathological angiogenesis in AMD is associated with pro-inflammatory microglia activation. Recently we identified that IGFBPL1 (insulin-like growth factor binding protein-like protein 1) suppresses microglia activation in the retina. In this study, we evaluate the effects of IGFBPL1 in the laser-induced choroidal neovascularization (CNV) model of mice and compare its effectiveness with anti-VEGFa therapy.

Methods : Adult C57BL/6 mice were randomly assigned to treatment of IGFBPL1 or anti-VEGFa antibody. Laser lesions were induced with a 532-nm laser (150 mW, spot size: 50 μm, pulse: 50 ms) using a slit-lamp delivery system. IGFBPL1 (100 ng in 1 µl PBS), anti-VEGFa (100 ng in 1 µl PBS), or 1 µl sterile PBS control was delivered intravitreally as a bolus. The CNV development was assessed at 7 days post injury by fluorescent angiography (FA) and Optical Coherence Tomography (OCT) as well as by immunolabeling in retinal flat mounts and RT-PCR quantification of pro-inflammatory cytokines. Direct effects of IGFBPL1 on blood vessel endothelial cells were studied using human retinal endothelial cell (HREC) cultures using the tube formation assay and Western blot analysis of VEGFa expression.

Results : IGFBPL1 treatment caused significant reductions in the fluorescein leakage and the size of laser lesion spot. Immunolabeling of the retina indicated substantial reductions of lectin-positive endothelial cells and infiltrating microglia as well as the suppression of pro-inflammatory cytokines, including Interleukin 1β (IL-1β), Tumor necrosis factor α (TNFα), and cyclooxygenase-2 (COX-2), in IGFBPL1 treated mice compared to control mice. These effects of IGFBPL1 were comparable with that of anti-VEGFa (100 ng) administration. IGFBPL1 showed no direct effect in tube formation assays or on VEGFa expression in HREC cultures.

Conclusions : The present data indicate that IGFBPL1 suppresses inflammatory angiogenesis through modulation of microglia activation. IGFBPL1 might present a promising therapeutic agent for AMD when is used alone, as a supplementary or combined therapy in anti-VEGFa resistant patients.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.