Glaucoma cure may lie in targeting 'stiff cells' that impede fluid drainage

Date: Sep-15-2014A unique international study that is unusual because it points to a mechanical

feature of cells as a cause of disease suggests glaucoma arises when certain cells in the eye

become stiff and impede drainage of fluid, causing pressure to build up. Treatments that target

this stiffness could lead to a cure for glaucoma, say the researchers.

Researchers say drugs that target the stiffness of the cells lining the Schlemm's canal could lead to a cure for glaucoma.

Glaucoma - a group of conditions that damage the optic nerve - is the second leading cause

of blindness globally, after cataracts. It is caused by build-up of fluid in the eye, resulting

in high pressure.

According to the US volunteer organization Prevent Blindness, there are currently over 2.7 million Americans aged 40

and older living with open-angle glaucoma - the kind that primarily affects people of African or

European origin.

For 150 years, scientists have been trying to discover what causes the blockage that stops the

aqueous humor - the clear fluid that nourishes the eye and maintains pressure inside the eyeball

- from draining properly, causing pressure to build up, which, in turn, damages the optic nerve at

the back of the eye.

Blockage in canal that drains the eye caused by faulty cells lining the walls

Now, a unique study led by Mark Johnson, a professor of biomedical engineering and mechanical

engineering at Northwestern University in Evanston, IL, reveals that the cause of the blockage

is a fault in the endothelial cells that line the canal - known as Schlemm's canal - through

which the fluid drains from the eye.

The researchers describe their findings in the Proceedings of the National Academy of

Sciences (PNAS).

The porous cells lining the walls of Schlemm's canal help control the drainage of fluid from

the eye. If, however, they become too stiff, it is more difficult for them to form pores, which

impedes the flow of fluid out of the eye, and so builds up pressure.

This is what Prof. Johnson and colleagues discovered when they compared cultured endothelial

cells isolated from the inner walls of Schlemm's canals of healthy eyes and eyes affected

by glaucoma.

For their study, they compared the cells from healthy and diseased eyes using "atomic force

microscopy, optical magnetic twisting cytometry, and a unique cell perfusion apparatus."

Cell stiffness likely part of a dynamic process involving genes that respond to changes

But the stiffness problem appears to be more than a straightforward mechanical fault in the

plumbing of the eye. The researchers also found stiffness correlated with an "enhanced

sensitivity to the mechanical microenvironment" of the cells, and this included changes in key

genes.

Thus, they suggest the lining of the Schlemm's canal is a dynamic material that responds and

adapts to mechanical strain, using pore formation as a way to control the resistance to aqueous

humor outflow. However, in eyes affected by glaucoma, this dynamic, responsive process becomes

impaired.

Prof. Johnson, who is also a professor of ophthalmology, says drugs that target the

stiffness of the cells lining the Schlemm's canal could lead to a cure for

glaucoma. He adds:

"The work appears to be one of the first times that the methods of mechanobiology - the study of

the mechanical characteristics of cells - have been used to show that dysfunctional cell

mechanics lies at the heart of a disease process."

In June 2014, a group of engineers at the University of Washington in Seattle reported they

are designing a sensor that can be implanted in the eye to monitor

pressure. They hope their permanent implant will be able to continuously monitor hard-to-measure changes in eye pressure.

Written by Catharine Paddock PhD

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Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.