Silencing of S100A4, a metastasis-associated protein, inhibits retinal neovascularization via the downregulation of BDNF in oxygen-induced ischaemic retinopathy.

Abstract

BackgroundTo investigate the underlying mechanism of S100A4 function and whether it has a role in retinal neovascularization (RNV) in a mouse model of oxygen-induced retinopathy (OIR).MethodsRetinas from a mouse model of OIR were treated with and without an intravitreous injection of adenoviral-S100A4-RNAi or adenoviral green fluorescence protein (GFP) at postnatal day 12 (P12). At P17, the efficacy of adenoviral gene transfer was assessed using fluorescence microscopy and western blot analysis. RNV was evaluated by whole-mount immunofluorescence staining of the mouse retina and by counting the number of pre-retinal neovascular cells. Protein and mRNA expression levels of S100A4, brain-derived growth factor (BDNF), and vascular endothelial growth factor (VEGF) were measured using western blot analysis and real-time PCR.ResultsRetinal S100A4 levels were positively correlated with the progression of RNV. In the OIR-S100A4-RNAi group, both protein and mRNA expression levels of S100A4 in the retina significantly decreased at P17 compared with those in the OIR group. Ad-S100A4-RNAi transfer was clearly demonstrated by GFP fluorescence in many layers of the retina 5 days after the Ad-S100A4-RNAi transfer. Whole-mount immunofluorescence staining of the retina and quantification of the pre-retinal neovascular cells demonstrated that RNV was significantly inhibited. Meanwhile, the levels of the transcription and translation of BDNF, VEGF, and hypoxia-inducible factor-1α (HIF-1α) significantly decreased in the OIR-S100A4-RNAi group.ConclusionsAd-S100A4-RNAi transfer ameliorates RNV. The related mechanism may involve silencing S100A4 to decrease the activation of BDNF, which downregulates VEGF expression via HIF-1α. This finding could provide a new therapeutic target for the treatment of ocular neovascularization diseases.