Bioprinted 3D Outer Retina Barrier Uncovers RPE-dependent Choroidal Phenotype in Advanced Macular Degeneration

Abstract

Age-related macular degeneration (AMD), a leading cause of blindness, initiates in the outer-blood-retina-barrier (oBRB) formed by Retinal pigment epithelium (RPE), Bruch’s membrane, and choriocapillaris. The mechanism of AMD initiation and progression remain poorly understood due to the lack of physiologically relevant oBRB models. We engineered a native-like 3D-oBRB tissue by bioprinting endothelial cells, pericytes, and fibroblasts on the basal side of a biodegradable scaffold and establishing an RPE monolayer on top. In this 3D-oBRB, a fully-polarized RPE monolayer with apical processes and basal infoldings provides barrier resistance, induces fenestration and choroid-specific gene expression in the choriocapillaris, and supports the formation of a Bruch’s-like membrane that allows tissue integration in rat eyes. Complement activation in the 3D-oBRB triggers dry-AMD phenotypes (including subRPE drusen and choriocapillaris degeneration), and hypoxia activated HIF-α induces wet-AMD phenotypes (choriocapillaris neovascularization). Anti-VEGF drug treatment suppresses neovascularization - validating this model for clinical translation and drug discovery.

Retinal Cell Transplantation, Biomaterials, and In Vitro Models for Developing Next-generation Therapies of Age-related Macular Degeneration

“…Recent breakthroughs have overcome the frustrations of past attempts and have already identified potential therapeutic targets. 84 , 86 , 87 , 102 These novel data support continued exploration of RPE-choroid co-cultures by in vivo testing to determine their potential as a tissue-replacement strategy. Further development of these models should also provide a platform to test potential therapeutic agents before committing to expensive animal studies.…”

“…A second example of direct RPE and endothelial cells was recently reported as an unreviewed preprint on Research Square . 87 These authors extended their studies with the electrospun PLGA scaffold (see the Section “Scaffolds Composed of Synthetic Materials”, Fig. 2B ), 65 by bioprinting endothelia, fibroblasts, and pericytes on the side of the scaffold opposite the RPE.…”

Balance between the cell viability and death in 3D

“…Spheroid cultures can furthermore help investigate the fusion and functional integration of multiple cell types. In the case of assembloids, such interactions are useful in tissue engineering and neurodevelopmental disease modeling studies, such as Timothy syndrome [16], macular degeneration [17], regeneration of tooth tissue [18] and SARS-CoV-2 neuropathology infection models [19]. Here, the viability of cells in the core rather than necrosis is more important for successful application.…”