Project description:Diabetic retinopathy (DR), the leading cause of blindness in working-age adults, is thought to be primarily a microvascular complication of diabetes. As a central element of the retinal neurovascular unit, Müller cells, the major macroglia of the retina, are important for maintaining a healthy and functional retina and play a critical role in several pathological events during DR disease progression. Here, we aim to improve our understanding of Müller cell-specific signalling pathways that are altered during DR disease progression in order to develop novel gene therapy strategies that target Müller cells. We used a multi-omics approach on purified Müller cells from 6-month-old control and diabetic db/db mice, including (i) RNA-seq followed by oPOSSUM-3 transcription factor (TF) binding site cluster analysis, (ii) glial chromatin landscape analysis by ATAC-seq, and (iii) Müller cell proteomics by MS/MS mass spectrometry. This led to the identification of the glucocorticoid receptor (GR, gene ID: Nr3c1) most highly expressed in Müller cells. In cells from diabetic mice, GR mRNA and protein expression is significantly reduced and its target gene cluster downregulated in Müller cells. Importantly, GR was identified as a potential master regulator not only by oPOSSUM analysis based on differentially expressed mRNA in Müller cells, but also validated by the ATAC-seq approach. In an in vitro cortisol-stimulated retinal explant model cortisol not only increased GR phosphorylation, but also induced changes in the expression of known downstream GR target genes. Finally, we evaluated whether AAV-mediated GR overexpression in Müller cells improves retinal functionality and we found moderate improvements indicated by electroretinography. While synthetic and topical glucocorticoids are widely used in ophthalmology with undeniable beneficial effects, our study provides valuable new insight into the role of GR signalling and glial alterations in the diabetic retina. This supports the therapeutic concept of locally enhancing the GR signaling axis. Our findings of reduced GR levels in Müller cells of the diabetic retina suggests that therapeutic approaches should aim at increasing the expression of the receptor rather than adding more ligand.

Project description:Diabetic retinopathy (DR), the leading cause of blindness in working-age adults, is thought to be primarily a microvascular complication of diabetes. Müller cells, the major macroglia of the retina, are important for maintaining a healthy and functional retina and play a critical role in several pathological events during DR disease progression as they are a central element of the retinal neurovascular unit. Here, we aim to improve our understanding of Müller cell-specific signaling pathways that are altered during disease progression in order to develop novel gene therapy strategies targeting Müller cells in DR. To achieve this, we used a multi-omics approach on purified Müller cells from 6-month-old control and diabetic db/db mice, including (i) RNA-seq followed by oPOSSUM-3 transcription factor (TF) binding site cluster analysis, (ii) glial chromatin landscape analysis by ATAC-seq, and (iii) Müller cell proteomics by MS/MS mass spectrometry. This led to the identification of the glucocorticoid receptor (GR, gene ID: Nr3c1) as the most promising candidate. Its transcripts and protein were most highly expressed in Müller cells and significantly reduced in cells from diabetic mice, its target gene cluster was downregulated in Müller cells from diabetic animals, and importantly, it was identified as a potential master regulator not only by oPOSSUM analysis based on differentially expressed mRNA in Müller cells, but also validated by the ATAC-seq approach. Next, we investigated the effect of GR modulation in an in vitro cortisol-stimulated retinal explant model. Cortisol not only increased GR phosphorylation levels, but also induced changes in the expression of known downstream GR target genes. Finally, we evaluated whether AAV-mediated GR overexpression in Müller cells improves retinal functionality and found moderate functional improvements in electroretinogram recordings. Although synthetic and topical glucocorticoids are widely used in ophthalmology with undeniable beneficial effects, our study provides valuable new insights into the role of GR signaling and glial alterations in the diabetic retina and thus supports the therapeutic concept of locally enhancing the GR signaling axis. However, our finding of reduced GR levels in Müller cells of the diabetic retina suggests that therapeutic approaches should aim at increasing the expression of the receptor rather than adding more ligands. This may result in optimized local efficacy with fewer systemic unwarranted side effects.

Project description:Previous studies have demonstrated the dynamic changes in chromatin structure during retinal development that correlate with changes in gene expression. However, a major limitation of those prior studies was the lack of cellular resolution. Here, we integrate single-cell (sc) RNA-seq and scATAC-seq with bulk retinal data sets to identify cell type–specific changes in the chromatin structure during development. Although most genes’ promoter activity is strongly correlated with chromatin accessibility, we discovered several hundred genes that were transcriptionally silent but had accessible chromatin at their promoters. Most of those silent/accessible gene promoters were in the Müller glial cells. The Müller cells are radial glia of the retina and perform a variety of essential functions to maintain retinal homeostasis and respond to stress, injury, or disease. The silent/accessible genes in Müller glia are enriched in pathways related to inflammation, angiogenesis, and other types of cell-cell signaling and were rapidly activated when we tested 15 different physiologically relevant conditions to mimic retinal stress, injury, or disease in human and murine retinae. We refer to these as “pliancy genes” because they allow the Müller glia to rapidly change their gene expression and cellular state in response to different types of retinal insults. The Müller glial cell pliancy program is established during development, and we demonstrate that pliancy genes are necessary and sufficient for regulating inflammation in the murine retina in vivo. In zebrafish, Müller glia can de-differentiate and form retinal progenitor cells that replace lost neurons. The pro-inflammatory pliancy gene cascade is not activated in zebrafish Müller glia following injury, and we propose a model in which species-specific pliancy programs underly the differential response to retinal damage in species that can regenerate retinal neurons (zebrafish) versus those that cannot (humans and mice).

			Action	DRS
	Cell2_manitol_3502.d.zip	Other
	Cell3_manitol_3503.d.zip	Other
	Cell4_manitol_3504.d.zip	Other
	Cell5_HG_3505.d.zip	Other
	Cell6_HG_3506.d.zip	Other

Dataset Information

Proteomics analysis of small extracellular vesicles derived from human retinal Müller glial cells under mannitol control and high glucose in vitro

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