Eye on a Chip: Microfluidic In Vitro Model of Blood-Retinal Barrier

Abstract

The efficiency of drug development process has been continuously decreased during last decades. Recently, micro engineering tech-nology have enabled researchers to develop advanced in vitro drug test platform such as organ-on-chip system that is expected to in-novate current drug discovery process. Although some leading start-up companies are trying to commercialize the organ on chip, the ultimate goal creating simple but precise in vitro model have long way to go. Despite the importance of blood vessel in various pathogenesis, current organ on chip models have missed the organ-specific blood vessel pathophysiology. In parallel with organ on chip technologies, advanced three-dimensional in vitro blood vessel model have been developed during last decade. Either the blood vessel model and the organ on chip have shed a light to the next generation of drug development process, combining the two technologies would be another step towards the development of innovative in vitro drug test model. To this end, this thesis first describes the method to create in vivo like blood vessel model by mimicking natural morphogenesis of the human primary endothelial cells. Effect of bio-mechanical stimulus exerted by interstitial flow (IF) on the development pro-cess of the model was studied. A minute rate of IF was introduced simply by hydrostatic pressure and visualized by fluorescence re-covery after photobleaching (FRAP). Series of experiments with various direction and sequence of the applied IF revealed the strong directional bias of the angiogenic sprouting into the opposite direction of the IF, which could be used as angiogenic switch to set the model in angiogenic or non-angiogenic condition. The blood vessel model could be applied to reconstitute retinal pigment epithelium (RPE) – choroid system of the eye, owing to the morphological similarity of the two system. The device design was modified and optimized to introduce RPE cells to mimic cross sectional structure of the RPE-choroid system. Treatment of pro- and anti- angiogenic factors allowed the in vitro model to quantita-tively simulate pathogenesis and treatment of wet type age related macula degeneration (wet-AMD) which causes blindness in many elderly people. The blood vessel model has potential to be used for various application, including unveiling the biochemical or biomechanical regulation of angiogenesis and evaluation of anti-angiogenic drug candidates. Moreover, the model would be applied to reconstitute various organ specific endothelial physiology, such as RPE-choroid system as described here, which would help predicting the organ specific pathophysiology in response to the drug can-didates in vitro.