Kellogg scientist believes discovery will "buy time" to repair retinal detachments
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One of the most common causes of vision loss is retinal detachment. Over the course of a lifetime, one person in 300 will experience a retinal detachment, usually from an event like a retinal tear or trauma, but also from diseases like diabetes or even macular degeneration. Retina specialist David N. Zacks, M.D., Ph.D., has been searching for a way to save vision in these people.
The retina's photoreceptors get their nourishment from the layers of cells beneath it. When they become separated from this nutritional sourcethey begin to die through a process of programmed cell death that scientists call "apoptosis." Since apoptosis begins within hours of a retinal detachment, the sooner the retina can be reattached, the better for the patient's vision. Regrettably, it is not always possible to perform a reattachment quickly. "If there were a way to postpone the start of programmed cell death," says Dr. Zacks, "tens of thousands of patients would benefit."
Dr. Zacks and his colleagues knew that a protein named XIAP (X-linked inhibitor of apoptosis) had a strong protective effect for cells in other diseases. Under the right circumstances XIAP could suppress the "cascade" of cell death by blocking the molecules (called caspases) that are responsible for apoptosis. The research team theorized that introducing XIAP into the retina would reduce the level of caspase activity and thereby increase the number of surviving photoreceptors.
Their theory turned out to be correct. In two groups of animals (one that received XIAP and one that did not) the scientists detached the retina. They found less caspase activity and fewer cells entering the apoptotic cascade in the XIAP group than in the control group. Most importantly, this resulted in more photoreceptor cells surviving long-term detachments in the XIAP-treated group.
"XIAP is not a treatment for retinal detachment," emphasizes Dr. Zacks. "It is simply a way to preserve photoreceptors while the underlying disease process is being addressed." If XIAP is successful in humans, this treatment could buy precious time until surgeons can reattach the retina and provide nourishment to the cells once again.
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