Abstract
Purpose :
In spite of comprehensive research over the last decades, there is often no treatment available for many retinal diseases, due to a lack of suitable in vitro models. We, hence, combined advanced microfabrication and stem cell technology to develop a human Retina-on-a-Chip (RoC) that embeds all relevant retinal cell types in a physiological microenvironment with vasculature-like supply.
Methods :
The chip-platform is fabricated using polymethylmethacrylate (PMMA) as base material. To realize a complex 3D environment within the RoC, microchannels and -structures were cut into several PMMA-layers with different heights via laser-assisted microfabrication. To separate the perfusion channels from the tissue compartments, we integrated isoporous membranes to emulate the vasculature microenvironment. The whole RoC was assembled via solvent bonding technique using defined amounts of ethanol, controlled pressure onto the layers and a convection oven. To generate the retinal tissue we combined retinal organoids and retinal pigment epithel derived from the same human induced pluripotent stem cells in the tissue compartments. Finally, for the light exposure, we developed an illumination device based on LED-arrays integrated into 3D-printed housings.
Results :
The developed microphysiological RoC enabled the generation of a 3D tissue featuring more than seven different cell types in a physiological multi-layer structure. Further, the RoC was able to support a stable long-term culture and to recapitulate the constant recycling process of photoreceptor outer-segments, which is a key function of the human retina. The choice of PMMA as base material provides a key advantage compared to polydimethylsiloxane (PDMS), which is commonly used for organ-on-chips (OoCs): PMMA features a much lower absorption of hydrophobic molecules. With the illumination-platform, it was possible to control the light intensity over culture periods and to apply defined exposure patterns to mimic both physiological day/night changes and light-toxicity.
Conclusions :
Combining the precise microengineering of OoCs with the biological self-assembly of organoids, we generated an in vitro model of the human retina with so-far unmatched functionality and the capacity for controlled light exposure. Thereby, the developed RoC is versatile for disease modeling, personalized medicine and toxicity screening.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.