Abstract: Age-related macular degeneration (AMD) is a leading cause of vision loss, yet current preclinical models fail to replicate the complexity of human retinal tissue. Traditional animal models and 2D in-vitro cultures lack the spatial organization necessary for modeling key cellular interactions, limiting their relevance for disease research and therapeutic screening. To address this, we have developed a multilayered 3D bioprinted retinal model by integrating enriched retinal progenitor populations into engineered constructs designed to mimic the human retina. We first established iPSC reporter lines with fluorescent tags to track and purify photoreceptor and bipolar cell progenitors, enabling the development of efficient cell purification strategies. These purified progenitor cells were maintained in culture as retinal spheroids, preserving their viability and differentiation potential until their use in bioprinting. Furthermore, we systematically tested various bioink formulations incorporating biologically relevant components of the retinal extracellular matrix, identifying an optimal composition that supports the structured deposition of retinal cells onto mature retinal pigment epithelium (RPE). Using this optimized bioink and bioprinting parameters, we successfully generated stable 3D scaffolds that remained intact for at least 20 days, maintaining an overall cell viability of >70%. Retinal cells bioprinted on top of RPE demonstrated superior survival, stable proliferation, and a more homogeneous distribution within the scaffold compared to those printed directly onto plastic substrates. These results highlight the importance of a biomimetic microenvironment in promoting the stability and functionality of bioprinted retinal constructs. Future efforts will focus on incorporating additional neuronal layers, such as retinal ganglion cells, enhancing synaptic connectivity, and integrating endothelial cells beneath the RPE to model the blood-retinal barrier. This work establishes a robust foundation for the development of physiologically relevant retinal models, providing a powerful tool for AMD research, drug discovery, and preclinical testing.
Funding Source: This research was funded by the European Commission (HORIZON-MSCA-2021-PF-01, iRETINA, Grant 101062218) and the Regional Government of Andalusia, Spain (I+D+i in Biomedicine and Health Sciences 2022, Project PI-0044-2022).
