OUR EYES have inbuilt protective mechanisms, and scientists may in future be able to exploit them to delay the onset of inherited blindness, according to an expert who visited Dublin last week.
When light-sensitive cells called photoreceptors at the back of the eye die, they are not replaced, but in forms of inherited blindness these cells may survive several decades before dying, explained John Ash, professor of ophthalmology at the University of Oklahoma Health Sciences Center.
“Generally you have patients who will inherit a mutation that will ultimately cause them to go blind. They get that gene at conception and yet they go through normal development and might live for 50, 60 or 70 years and still have good vision,” said Prof Ash ahead of speaking on Friday at the Retina 2010 conference, hosted by Irish charity Fighting Blindness.
“So we went after trying to identify what the potential mechanism was that kept the cells alive for that long. If we find it then maybe we could put it back, or enhance that mechanism so we can keep the cells alive even longer, essentially delay even further the onset of blindness.”
His group looked at the effects of stress on cells in the retina. “We and others have found that there’s a response in the retina when it is under stress, and part of that response is to increase the expression of cytokines, a group of proteins that . . . induce the cell to survive.”
They then altered elements of the protective pathways in a pre-clinical model to see the effects on retinal cells.
“When we knocked it out they had normal function, no problems. But if we then stressed the retina, the photoreceptors in particular, then they died almost instantly,” he said.
Prof Ash’s group is now looking at ways to beef up the protective biochemical pathways in ways that could help people with inherited mutations delay the loss of light-sensitive cells.
“We don’t need to reinvent the wheel – the wheel has been invented – we just need to figure out how to drive it better,” he said, noting that the protective approach could also have possible applications in other neurodegenerative conditions.
“But there’s no short cut. Even if I had a drug in my hand right now, it would be a minimum of 10 years before a lot of people would benefit from that.”
