Multi-corneal barrier-on-a-chip to recapitulate eye blinking shear stress forces

Human corneal epithelium coexists with tear fluids and shows its barrier functionality under the dynamic conditions of eye blinking. However, the current in vitro cell culture settings for corneal epithelial cells lack the dynamic flow conditions to recapitulate the shear stress of eye blinking, hindering corneal function evaluation. We developed a microfluidic platform enabling the dynamic culture of the human corneal barrier with recapitulation of eye blinking. The device consisted of upper and lower channels separated by a porous membrane. Human corneal epithelial cells (HCE-T) were seeded on the porous membrane (upper channel) and cultured for ten days. The cells formed a barrier with high expression of zonula occludens 1 (ZO-1) tight junction protein on day seven, and the translocation of fluorescein sodium across the barrier in the microfluidic device was comparable to that in the transwell system, used as a control. Then, bidirectional and unidirectional flows were applied in the upper and lower channels, respectively, and the cells in the upper channels were stimulated with 0.6 dyn s cm^-2 shear stress. After 24 h, while the fluid stimuli did not affect cell adhesion, they facilitated the expression of cytokeratin 19 (CK-19) intermediate filaments in cells, indicating the strengthening of the barrier function. Furthermore, morphological single-cell analysis revealed an increase in the cell body area rather than nuclei. We envision that this multi-corneal barrier-on-a-chip device will unlock new possibilities in ophthalmic drug development and will be useful for studying the effects of eye blinking shear stress on the ocular surface.