Effect of glucocorticoids on neuronal and vascular pathology in a transgenic model of selective Muller cell ablation

Retinal diseases such as macular telangiectasis type 2 (MacTel), age-related macular degeneration (AMD) and diabetic retinopathy (DR) affect both neurons and blood vessels. Treatments addressing both at the same time might have advantages over more specific approaches, such as vascular endothelial growth factor (VEGF) inhibitors, which are used to treat vascular leak but are suspected to have a neurotoxic effect. Here, we studied the effects of an intravitreal injection of triamcinolone acetonide (TA) in a transgenic model in which patchy Muller cell ablation leads to photoreceptor degeneration, vascular leak, and intraretinal neovascularization. TA was injected 4 days before Muller cell ablation. Changes in photoreceptors, microglia and Muller cells, retinal vasculature, differential expression of p75 neurotrophin receptor (p75(NTR)), tumor necrosis factor-alpha (TNF alpha), the precursor and mature forms of neurotrophin 3 (pro-NT3 and mature NT3) and activation of the p53 and p38 stress-activated protein kinase (p38/SAPK) signaling pathways were examined. We found that TA prevented photoreceptor degeneration and inhibited activation of microglial and Muller cells. TA attenuated Muller cell loss and inhibited overexpression of p75(NTR), TNF alpha, pro-NT, and the activation of p53 and p38/SAPK signaling pathways. TA not only prevented the development of retinal vascular lesions but also inhibited fluorescein leakage from established vascular lesions. TA inhibited overexpression of VEGF in transgenic mice but without affecting its basal level expression in the normal retina. Our data suggest that glucocorticoid treatment may be beneficial for treatment of retinal diseases such as MacTel, AMD, and DR that affect both neurons and the vasculature. GLIA 2014;62:1110-1124