Neuroprotection and Inhibition of Blood-Retinal Barrier Breakdown In a Transgenic Model of Conditional Müller Cell Ablation

Abstract

Purpose: : Since Müller glia interact closely with both retinal neurons and blood vessels, Müller cell dysfunction may disrupt both systems. We have developed a novel transgenic model of conditional Müller cell ablation. This study aimed to test strategies to prevent the photoreceptor death and blood-retinal barrier breakdown that occur in this transgenic model.

Methods: : We generated a DNA construct containing a Müller cell-specific promoter driving a tamoxifen-inducible form of Cre recombinase (CreER). The cell-specific promoter contained a fragment of regulatory region of the retinaldehyde binding protein 1 gene (Rlbp1). Rlbp1-CreER transgenic mice were crossed with Rosa-DTA176 mice for inducible, Muller cell-specific intracellular expression of an attenuated form of diphtheria fragment A. Dynamic changes in Müller glia, photoreceptors and retinal vasculature were investigated after switching on the DTA176 toxic gene expression with tamoxifen. Cilliary neurotrophic factor (CNTF) and VEGFB20.4.1.1, a VEGF antibody that binds both human and murine VEGF-A, were injected intravitreally to examine their effects on photoreceptor death and BRB breakdown at different stages after conditional Müller cell ablation.

Results: : Müller cell ablation led to rapid photoreceptor apoptosis, blood-retinal barrier breakdown and, later, deep retinal neovascularization. Intravitreal injection of CNTF inhibited photoreceptor apoptosis but had no effect on the vasculopathy. Blocking VEGF action with intravitreal injection of VEGFB20.4.1.1 dramatically attenuated vascular leak but did not rescue photoreceptors.

Conclusions: : Our results demonstrate that Müller glia dysfunction can be the upstream cause of both neuronal and vascular pathology, which can occur independently in the retina. Our findings also show that Müller glia dysfunction may have a so far unappreciated role and be a mechanistic link between neuronal and vascular pathologies in retinal diseases.

Keywords: Muller cells • photoreceptors • retinal neovascularization