Abstract

Background:Platelet factor 4 (PF4/CXCL4) is a chemokine with reported anti-angiogenic and immunomodulatory properties; however, the role of PF4 in neovascular age-related macular degeneration (nAMD) remains unclear. Thus, this study aimed to evaluate the therapeutic potential of PF4 in experimental models of ocular pathological neovascularization and explored the underlying mechanisms.Methods:PF4 expression was assessed in a laser-induced choroidal neovascularization (CNV) mouse model using quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assay (ELISA), and immunofluorescence. Recombinant PF4 was administered intravitreally in laser-induced CNV mice and very low-density lipoprotein receptor knockout (Vldlr⁻/⁻) mice, a model of spontaneous retinal neovascularization with retinal angiomatous proliferation (RAP)-like lesions. Pathological neovascularization and vascular leakage were quantified by fundus fluorescein angiography and choroidal/retinal flat-mount analyses. Immunofluorescence, qRT-PCR, and RNA sequencing were employed to evaluate inflammatory responses. Moreover, the effects of PF4 on vascular endothelial growth factor (VEGF)-induced proliferation, migration, and tube formation of human retinal microvascular endothelial cells were examined in vitro, and VEGF-mediated signaling was analyzed by Western blotting. Ocular safety was assessed by optical coherence tomography (OCT), electroretinography (ERG), hematoxylin and eosin (H&E) staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay.Results:Intravitreal PF4 significantly reduced pathological neovascularization and vascular leakage in both models and attenuated intraocular inflammation, as indicated by decreased expression of proinflammatory cytokines and reduced microglial/macrophage recruitment. PF4 inhibited VEGF-induced endothelial cell proliferation, migration, and tube formation in vitro. Mechanistically, PF4 downregulated VEGF expression in CNV lesio