Targeting Müller cells for therapy of diabetic retinopathy

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Diabetic retinopathy (DR) is a retinal disease of highest relevance in societies of developed countries being the most prevalent reason of vision loss in the working population. Müller cells, the principal macroglia of the retina, undergo major changes in gene expression associated with partial loss of their cell functions in DR. Strikingly little is known about the modulation and mechanistic relevance of this Müller cell activation. The goal of our study is to significantly improve our understanding of the role of this glial reaction and to promote neuronal survival in DR by manipulating Müller cell gene expression. Mice carrying a mutant leptin receptor (db/db mice) will be used to model type II diabetes and associated retinal changes. To generate a constantly high neuronprotective microenvironment in the diabetic retina, we aim to overexpress the neuroprotective factor Norrin in Müller cells of db/db mice by specifically transducing them with ShH10, an adeno-associated virus serotype with Müller cell tropism. Using tools for expression analysis (qRT-PCR, Western blot) and to test for Müller cell and retinal functions (patch-clamp, electroretinogram, fluorescence angiography), we will validate the therapeutic potential of this approach. Next, we seek to overexpress the potassium channel Kir4.1 in Müller cells as it is the essential potassium channel for Müller cell homeostatic functions that gets lost in the diabetic retina. By Kir4.1 re-expression, we will test the hypothesis that a stabilized neuron-supportive Müller cell phenotype in the diabetic retina has the potential to slow down or even halt disease progression. In parallel to these proof of principle experiments, comprehensive data on the gene expression (RNA and protein) from Müller glia isolated from healthy and diabetic retinae in comparison with expression data collected from microglia, endothelial cells and retinal neurons will be generated to identify novel candidate genes specifically involved in Müller cell activation. This costly and laborious approach will give intriguing insights into the interplay of these respective cell types in the context of DR. Integration of these data with data from genome-wide association studies for DR may identify Müller cell genes potentially serving as targets for novel DR therapies in humans. After functional characterization of most promising candidate genes, we aim at implementing ShH10-driven modulation of one selected candidate to preserve key Müller cell functions fostering neuronal survival in the diabetic retina. In sum, we are confident that data collected in the present project will considerably contribute to the development of novel long-term efficient treatment options for DR that to date cannot be satisfactorily addressed by conventional therapeutic approaches owing to its complex disease etiology.