Tiny lumps of calcium phosphate may be an important triggering factor for age-related macular degeneration (AMD), according to scientists at the University of Maryland School of Medicine (UM SOM). AMD is a degenerative eye disease that can cause severe vision loss and blindness.
Previous studies have shown that AMD develops slowly over decades, with the buildup of fatty protein deposits in the retina, which cause damage by blocking the flow of nutrients into the light-sensitive portion of the eye, and of waste products out. But, the origins of these deposits remained a mystery.
The research team studied retinal samples using X-ray diffraction and fluorescent staining chemicals from a group of elderly patients, some of whom had AMD. They found that the AMD samples contained tiny spherules of mineralized calcium phosphate known as hydroxyapatite, or HAP that comprises the hard part of bones and teeth, and had never been identified in that part of the eye before. Once these HAP chunks appear, the fatty protein material coalesces around it; over years, these globules build up. Researcher Imre Lengyel said, "We think HAP plays a key role in this process. This is a new explanation for how these deposits start."
Biochemist Richard Thompson said, "We had no idea that HAP might be involved. That's what makes this work so exciting. It opens up a lot of new research opportunities." Researchers are now looking into the possibility of using the presence of HAP as an early warning signal for AMD risk with a hope that this will aid early intervention before patients have suffered irreversible vision loss.
The article is published in the 'Proceedings of the National Academy of Sciences'.