While scientists have successfully modeled various “organ-on-a-chip” models, the eye is particularly challenging because the tear film periodically moves across its surface when we blink. , which was recently replicated in the new device.
The new tool — a “cornea on a chip” developed by researchers at Kyoto University in Japan — is the cornea, a transparent film at the front of the eye that covers the pupil, iris and anterior chamber.
This 3D printed device consists of four upper and four lower channels separated by a transparent polyester porous membrane. Human corneal cells were incubated in each upper channel for 7 days, during which time they grew, forming a solid barrier of cells on top of the membrane. Fluid is then pumped through the upper and lower chambers, applying pressure on both sides of the corneal tissue layers. This simulates a way in which the real cornea is stressed on one side by the blinking of the eyelid and the movement of tears, and on the other side by the fluid inside the eye.
When testing the “cornea-on-a-chip,” the researchers found that the simulated blinks actually changed the shape of corneal cells and increased their production of filaments, helping to keep the cells flexible and stretchable.
“It’s really interesting to find that blink-like stimuli have a direct biological effect on these cells,” says pharmaceutical scientist Rodi Abdalkader, who co-led the study with scientist Ken-ichiro Kamei. We blink our eyes so often without knowing it. With each blink, shear stress is exerted on the corneal barrier, causing the corneal counter-defense system to secrete filaments, such as keratin, to overcome the effects of stress. “
The researchers hope that once further developed, the technique could be used to study eye diseases and evaluate experimental drugs. A paper on the research was recently published in Lab on a Chip.
This isn’t the first chip we’ve seen to simulate blinking. Last year, a team at the University of Pennsylvania released a model that actually contained a moving gelatin slab “eyelid.”
An organ-on-a-chip is a microfluidic culture device consisting of a transparent, flexible polymer about the size of a computer memory stick that contains two parallel hollow channels separated by a porous membrane. Organ-specific cells were cultured on one side of the membrane in one channel, while vascular endothelial cells reproduced blood vessels in the other channel, and each channel was individually perfused with cell-type-specific media. The porous membrane allows the two compartments to communicate with each other and exchange molecules such as cytokines, growth factors and drugs, as well as drug breakdown products resulting from organ-specific metabolic activities.
An example of a need for animals in preclinical testing is the characterization of a drug’s “pharmacokinetics” (PK), which involves the quantification of its absorption, distribution, metabolism, and excretion (ADME), which together determine drug levels in the blood. These responses involve interactions between different organs connected by the vasculature that contains the flowing blood.
It is now possible to treat some of these really tricky chronic inflammatory diseases by designing experiments with some organs on a chip.
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