Abstract
Purpose:
TNF is a pivotal cytokine for the progression and clinico-pathological expression of EAU. Firstly, TNF regulates macrophage infiltration into the eye and, within the tissue, macrophage activation is responsible, in part, to the TNFR1-dependent tissue damage observed. After peak disease and damage, a persistent stage of EAU ensues (lasting up to 120 days). During this period a continual inflammatory infiltrate is observed alongside formation of retinal neovascular membranes (RNMs) and loss of remaining photoreceptors. Although TNF can induce VEGF secretion from macrophages and endothelial cells, the role of TNF during the later stages of EAU has not been defined. Our aim was to examine the impact of TNFR1-dependent TNF signalling on retinal angiogenesis in mice during late stage EAU.
Methods:
Disease progression was monitored in TNFR1-/- and wild type (WT) C57BL/6J mice through topical endoscopic fundal imaging (TEFI). At day 90 post immunisation (p.i.), collagen IV- immunofluorescence on retinal whole mounts was used to quantify morphologically determined angiogenesis (RNMs). Cellular infiltration was quantified by flow cytometry and gene expression of cytokines was analysed using qPCR.
Results:
Clinical disease in TNFR1-/- mice was previously described at a consistently lower level compared to WT. Here, we show there was no significant difference in cell numbers of CD4+ and CD11b+ cells in the eye at day 90. TNFR1-/- mice were, however, protected from developing angiogenesis reflected by not only a dramatic reduction in RNMs but also, when occurring, smaller angiogenic lesions. Despite equal infiltrating cell numbers, TNFR1-/- displayed a reduction in gene expression of pro-inflammatory and pro-angiogenic cytokines, in particular levels of IL-17A and TNF.
Conclusions:
Lack of active TNFR1 signalling suppresses inflammatory-mediated angiogenesis in the late stages of EAU, during which a reduction in cytokines that normally lead to macrophage activation and VEGF secretion is observed. Understanding the role of TNF in angiogenesis during uveitis may benefit the development of therapies targeting retinal angiogenesis, a major cause of vision loss.
Keywords: 746 uveitis-clinical/animal model •
700 retinal neovascularization •
557 inflammation