Introduction:: The retinal pigment epithelium (RPE) is the main component of the outer blood-retinal-barrier (BRB) and harmonizer of the ocular system by interacting with the choroid and neural retina. It forms the monolayer on the basement membrane called Bruch’s membrane (BM) and conducts the multifunctional role including phagocytosis of molecular waste and supporting phototransduction. However, due to its structural characteristics, cellular monolayer on the thin membrane, the recapitulation of the functional RPE in vitro has been hindered. In this study, the hybrid membrane printing technology, which can produce the cellular monolayer on the extracellular matrix-based basement membrane. Based on this technology, we finally fabricated the in vitro human RPE model with its natural functionalities. Furthermore, we confirmed the versatility of our model by evaluating the safety/effect of photobiomodulation (PBM) and analyzing the effect of smoking on the ocular system.
Materials and Methods:: The vitrified membrane and monolayer printing were developed and combined for hybrid printing technology. Briefly, the porcine BM-derived bioink was printed and crosslinked on the glass substrate and further incubation was conducted to remove water contents to form a thin ECM membrane. Then, the cell encapsulated in gelatin bioink was printed on the membrane, followed by incubation at 37 °C to form the cellular monolayer. The fabricated outer BRB model was analyzed in aspect of barrier, clearance, and visual functions. Finally, the exposure of the 670 nm of LED light and cigarette smoke extract was conducted for analyzing their effects on the human RPE.
Results, Conclusions, and Discussions:: The in vitro model, composed of RPE monolayer on the BM was fabricated by hybrid membrane printing technology and showed its functionalities. Based on this model, we confirmed that the PBM was safe to use and reduce the oxidative stress on RPE. Furthermore, we also observed that smoking damaged RPE and increase oxidative stress but antioxidant was insufficient to protect the RPE. Here, we developed the hybrid membrane printing technology for printing cellular monolayer and produced the outer BRB model. We confirmed that our model could be used for evaluating new treatments and understanding the pathogenesis of disease. We hope that this platform will aid in the development of treatments that will help patients with diseases related to the ocular system.
Acknowledgements (Optional): : This work was supported by the National Research Foundation (NRF) of Korea grants funded by the Korea government (MSIP) (NRF-2022R1A2C3004300 and NRF- 2021R1C1C1008042).