Retinal microglia are critical for subretinal neovascular formation
Ayumi Usui-Ouchi, … , Stephen Bravo, Martin Friedlander
Ayumi Usui-Ouchi, … , Stephen Bravo, Martin Friedlander
Published June 18, 2020; First published May 21, 2020
Citation Information: JCI Insight. 2020;5(12):e137317. https://doi.org/10.1172/jci.insight.137317.
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Research Article Angiogenesis Ophthalmology

Retinal microglia are critical for subretinal neovascular formation

Abstract

Abnormal subretinal neovascularization is a characteristic of vision-threatening retinal diseases, including macular telangiectasia (MacTel) and retinal angiomatous proliferation (RAP). Subretinal neovascular tufts and photoreceptor dysfunction are observed in very-low-density lipoprotein receptor (Vldlr–/–) mutant mice. These changes mirror those observed in patients with MacTel and RAP, but the pathogenesis is largely unknown. In this study, we show that retinal microglia were closely associated with retinal neovascular tufts in Vldlr–/– mice and retinal tissue from patients with MacTel; ablation of microglia/macrophages dramatically prevented formation of retinal neovascular tufts and improved neuronal function, as assessed by electroretinography. Vldlr–/– mice with retinal pigmented epithelium–specific (RPE-specific) Vegfa had greatly reduced subretinal infiltration of microglia/macrophages, subsequently reducing neovascular tufts. These findings highlight the contribution of microglia/macrophages to the pathogenesis of neovascularization, provide valuable clues regarding potential causative cellular mechanisms for subretinal neovascularization in patients with MacTel and RAP and suggest that targeting microglia activation may be a therapeutic option in these diseases.

Authors

Ayumi Usui-Ouchi, Yoshihiko Usui, Toshihide Kurihara, Edith Aguilar, Michael I. Dorrell, Yoichiro Ideguchi, Susumu Sakimoto, Stephen Bravo, Martin Friedlander

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Figure 1

Retinal microglia or macrophages are associated with subretinal neovascular angiomas in Vldlr–/– mice.

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Retinal microglia or macrophages are associated with subretinal neovascu...
(A) GS-lectin staining on cryosectioned Vldlr-/+; Cx3cr1GFP/+ and Vldlr–/–; Cx3cr1GFP/+ retinas at P27 (top) and flat-mounted Vldlr–/–; Cx3cr1GFP/+ retina in each retinal layer (bottom) indicate Cx3Cr1-GFP–positive microglia/macrophages (white arrows) in close proximity of abnormal angiomas in the outer nuclear layer and subretinal space in Vldlr–/–; Cx3cr1GFP/+ mice. (B) VEGF fundus autofluorescence by infrared reflectance (IR), indocyanine green angiography (ICG), and GFP in P40 Vldlr–/–; Cx3cr1GFP/+ mice showed that the pathological neovascular angiomas (yellow arrows) and the GFP-positive cells were aggregated close to the neovessels (yellow arrowheads). (C) IBA1-positive microglia/macrophages were localized in the outer nuclear layer and subretinal space in proximity of neovessels positive for collagen IV (Col IV; counterstained with DAPI, white arrows) in a retinal section of a macula from a patient with MacTel. (D) GS-lectin staining on cryosectioned P6, P10, or P13 Vldlr–/–; Cx3cr1GFP/+ retinas demonstrates that microglia (arrowheads) migrated into the subretinal space ahead of the neovessels (arrow). (E) Immunostaining for ZO1 in flat-mounted RPE at P14, P17, and P27 of Vldlr–/–; Cx3cr1GFP/+ mice. At P14, the first appearance of GFP-positive microglia/macrophages migrated into ZO1-positive RPE layer was observed (white arrow) with subsequent NV following. (F) Significantly upregulated genes between Vldlr–/– and Vldlr-/+ mice, as analyzed using a PCR array for angiogenesis, are shown (P < 0.05 and >1.5 fold change) The P values were calculated based on a Student’s t test of the replicate 2(- Delta Ct) values for each gene in the Vldlr-/ group and Vldlr-/+ groups. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 (n = 4 each). GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; RPE, retinal pigmented epithelium. Scale bars: 100 μm (A, C, and D); 50 μm (E).