Retinal Fibrosis Model
Introduction & Aim
Retinal fibrosis is a severe pathogenesis associated with different retinal diseases, such as age-related macular degeneration (AMD), which inevitably leads to vision loss in the affected individual. With a projected 288 million individuals suffering by 2040, AMD is the leading cause of vision loss worldwide. RPE cells becoming dysfunctional is believed to be one of the key elements of AMD disease progression. Especially epithelial-to-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells into myofibroblasts is a hallmark event initiating RPE-decoupling and aberrant extracellular matrix deposition contributing largely to the disintegration of the retina.
The aim of this study was in the first phase to establish scaffold-free human RPE microtissues (hRPE-MTs), which show native phenotype and tissue morphology such as epithelium formation, cell polarization, and up-regulation of RPE-typic functions. Based on the established 3D model, we were aiming to induce retinal fibrosis and develop suitable endpoints for quantification.
Methods
Scaffold-free 3D cell cultures of human RPE cells were aggregated by self-assembly. In-depth characterization of the model was conducted by whole transcriptome analysis, microtissue histology and ultrastructural analysis.
To recapitulate retinal fibrosis, microtissues were exposed to EMT-stimuli and subsequently cultured, allowing the hRPE-MTs to undergo EMT and become fibrotic. For quantification, hRPE-MTs were stained using quadruple staining for Fibronectin, Collagen-I, Phalloidin and DAPI and subsequently imaged by confocal spinning disc imaging. Additionally, secreted pro-Collagen-I levels in the supernatant were measured and transcriptomics was performed using TempO-Seq technology.
Results and conclusion
Primary human RPE cells aggregate to form viable microtissues, showing RPE-typical morphology and functionality. Upon disease induction, cells lose their phenotype and the microtissues undergo strong molecular and morphological changes: Upregulation of α-SMA, Fibronectin and Collagen-I expression, loss of polarization, loss of tight junctions, cytoskeleton stress fiber formation, loss of structure (RPE-decoupling/epithelial monolayer) and upregulation of EMT and Fibrosis-associated gene sets. Treatment with different small molecules targeting PDGFR-α/β, RHOa, RAR-α, and Alk5 inhibited fibrosis disease onset and stress fiber formation in the cytoskeleton.
The presented 3D cell culture-based retinal fibrosis model represents a promising platform for drug screening approaches, enabling the discovery and characterization of new anti-fibrotic drugs in a relevant in vitro set-up.
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