Introduction: Age-related macula degeneration (AMD) is a blinding neurodegenerative disease of the retina. It affects 4% of the population over 60. For over 90% of patients there is no cure due to cellular atrophy of the retina. Progressive deposit accumulation (drusen) under the retinal pigment epithelium (RPE) is the hallmark of the disease. Currently, no single (in vitro) model recapitulates this feature fully, which severely hampers pre-clinical and therapeutic research. Due to technical limitations so far, neither deposit initiation nor its consequences have been addressed in a fully controlled experimental set-up. We propose here to combine our expertise in subRPE deposit biology and our state-of-the-art 3D cellular bioprinting technology at Amsterdam UMC, to create and assess a fully controlled next-generation in vitro AMD model. This bioprinted model will consist of a monolayer of stem cell-derived RPE, a third-generation artificial Bruch’s membrane (BrM) and (a combination of) single artificial subRPE deposit components in between. These deposits will contain fully controlled amounts and types of subRPE deposit material. The model will help to understand better the process of drusen progression and disease.
Methodology: The ARPE-19 cell line was used for pilot experiments. Stem cell derived neuro-epithelial (RPE) cells and endothelial cells were generated and stored. They were characterised by light and confocal scanning microscopy, PCR and by transepithelial electrical resistance measurement. The 3D deposit AMD model was printed using the RegenHU 3D Discovery bioprinter. The deposit model was characterised by light microscopy, confocal scanning microscopy. Images were analysed using ImageJ software.
Results: Embryonic stem cell differentiated RPE cells showed extensive pigmentation, expression of RPE65 and BEST1 and developed high transepithelial electrical resistance over time (602.3 ±37.3 Ohm*cm2 at day 120). Embryonic stem cell differentiated endothelial cells showed positivity for CD31 and CA4. In parallel, AMD relevant deposit material, representing drusen, was embedded in a synthetic hydrogel and 3D bioprinted in different sizes. The 3D bioprinting showed high precision and reproducibility (SD< 0.04). The electromagnetic jetting technology resulted in homogenous distribution of AMD relevant deposit material in the printed hydrogel droplets. As a next step, ARPE-19 cells were seeded on top of the 3D bioprinted deposit droplets. As documented by confocal scanning microscopy, RPE cells showed partial attachment and grew over the edge of AMD relevant deposit material contained in hydrogel droplets.
Conclusions: Ready-to-use stem cell derived RPE and endothelial cells have been established. Using cellular 3D-bioprinting technology, we showed that it is possible to recreate a working artificial sub-RPE deposit model in a highly controlled experimental setup. Further characterization of this model is under progress.