Fluid movements on cornea replicated for improved drug tests

Researchers in Japan have developed a device that moves fluids over cornea cells, an advance that could lead to more accurate drug testing on the human eye.

Cornea-on-a-chip (Image: Kyoto University iCeMS)

The scientists at Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS) hope their findings, reported in Lab on a Chip, will help improve ophthalmic drug development and testing, and advance understanding of how blinking affects the corneal surface.

“4D tissue” building technique creates self curving synthetic cornea

The cornea is a transparent disc covering central surface of the eye and it acts as a protective barrier against dust, germs, and other potentially damaging objects.

Scientists can test ophthalmic drugs by administering them into rabbit’s eyes. Rabbits blink significantly less than humans, so drugs have more chance of permeating the rabbit’s cornea and enter into the eye. Alternatively, scientists use tiny wells containing human corneal cells. But here also, the cells aren’t exposed to the normal environment of a living human eye.

Kyoto University pharmaceutical scientist Rodi Abdalkader and micro-engineer Ken-ichiro Kamei collaborated to develop a device that overcomes these issues.

They 3D-printed a device that contains four upper and four lower channels, separated by a clear polyester porous membrane. Corneal cells are incubated in each upper channel on top of the membrane. After seven days, they are said to form a barrier of cells that separates the upper and lower channels. Fluid is then moved through the device to emulate the pressure exerted on one side of the cornea by a blinking eyelid and moving tears, and on the other side by the fluid of the inner eye.

They found that this movement changed the shape of the cells and increased the production of filaments, which keep corneal cells flexible and elastic.

“It was really interesting to find that an eye-blinking-like stimulus has a direct biological impact on these cells,” Abdalkader said in a statement. “We blink frequently and unconsciously all the time. With each blink, a shear stress is applied on the corneal barrier that causes the cornea counter-defence system to secrete fibrous filaments, like keratins, to overcome the effects of the stress.”

The device also allows testing of four different samples under similar conditions simultaneously.

“We believe this platform will pave the way for improved ocular drug development, and further investigations into the effects of the shear stress caused by eye blinking on the eye’s surface,” said Abdalkader.