Project description:Methods: Profiles of individual human retinal organoids (HRO) at 150, 200 and 250 days of development days were treated for 10 days with HBEGF and TNF, and compared to solvent controls (CTRL). N=6 HROs per timepoint and variable. Single-end sequencing with 30 Mio reads per sample was performed at a length of 75 bases on HiSeq2500 (Illumina). The sequence reads that passed quality filters were analyzed at the transcripts level. Results: Our data independently confirms that this protocol provides HROs with macular-like characteristics and shows low baseline variabilities for rods, cones and Müller glia. These features might be key for disease modeling, since most animal models lack a macula, and most other organoid protocols have low cone cell numbers. We found a significant reduction in the number of rod and cone photoreceptor cells after 10 days after HBEGF-TNF (HT) treatment. Specifically, some photoreceptors show pathologic changes, and some are apically displaced, with their nuclei protruding into or passing out of the retina. Histopathologic changes indicate photoreceptor extrusion of viable or dying cones and rods as a pathomechanism. Notably, photoreceptor displacement through the apical retinal border, and thus ectopy in the region of photoreceptor inner and outer segments, has been described in patients and animal models. In controls, photoreceptors were highly ordered, interspersed and interconnected with each other and with Müller glia processes, and these cell connections make up the outer limiting membrane. Upon HT, glial processes expanded in size, extended laterally along the retinal circumference, and replaced or covered photoreceptors over large areas – forming a seal-like glial scar. Taken together, HT induces photoreceptor degeneration via cell extrusion in conjunction with reactive gliosis, glial proliferation, retinal thickening/dyslamination, and glial seal-like scar formation, which reproduces a complex outer retinal atrophy. Interestingly, our transcriptome data revealed distinct gene expression patterns supporting our histological phenotype, specifically, cone and rod degeneration, reactive gliosis, glial proliferation, and photoreceptor cell extrusion. Conclusions: We show that combined application of HBEGF and TNF, two neuropathology associated factors, is sufficient to induce a complex human retinal pathology. We discovered cone and rod cell extrusion as a pathomechanism for photoreceptor degeneration and a potential interrelationship with glial pathologies. Pharmacological inhibitor experiments support this, and PIEZO1 and MAPK signaling as untapped therapeutic targets, even for complex pathologies. Thus, our model provides mechanistic access to several pathologic processes as well as pathogenic functions of inflammation and biomechanics.

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: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).

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MiRNA expression data from CD73-positive Rods, Müler glia and E 17.5 Retinal Progenitors

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