Identifying Hyperreflective Foci in Diabetic Retinopathy via VEGF-induced Local Self-Renewal of CX3CR1+ Vitreous Resident Macrophages

Abstract

<p>Intraretinal hyperreflective foci (HRF) are significant biomarkers for diabetic macular edema. However, HRF at the vitreoretinal interface (VRI) have not been examined in diabetic retinopathy (DR). A prospective observational clinical study with 162 consecutive eyes using OCT imaging showed significantly increased HRF at the VRI during DR progression (<em>P</em><0.01), which was reversed by anti-VEGF therapy. F4/80+ macrophages increased significantly at the VRI in Kimba (<em>vegfa</em>+/+) or Akimba (Akita × Kimba) mice (both <em>P</em><0.01), but not in diabetic Akita (<em>Ins2</em>+/-) mice, indicating macrophage activation was modulated by elevated VEGF rather than the diabetic milieu. Macrophage depletion significantly reduced HRF at the VRI (<em>P</em><0.01). Furthermore, BrdU administration in <em>Ccr2</em>rfp/+<em>Cx3cr1</em>gfp/+ <em>vegfa</em>+/- mice identified a significant contribution of M2-like tissue-resident macrophages (TRMs) at the VRI. Ki-67- and CD11b-positive cells were observed in preretinal tissues of DR patients while exposure of vitreal macrophages to vitreous derived from PDR patients induced a significant proliferation response <em>in vitro</em> (<em>P</em><0.01). Taken together, the evidence suggests that VEGF drives a local proliferation of vitreous resident macrophages (VRMs) at the VRI during DR. This phenomenon helps to explain the derivation and disease-relevance of the HRF lesions observed through OCT imaging in patients.<br> </p>