The leading cause of blindness in older American adults may have met its match.
A new study finds cholesterol-lowering drugs given in the form of eye drops cured macular degeneration in mice, fueling hopes the same treatment may work for humans.
Macular degeneration is the primary cause of blindness in U.S. adults aged 60 and over. The disease affects cells in the eye's macula -- which is the central part that allows people to see fine detail -- destroying central vision in the process, according to the National Eye Institutes. There is no treatment to restore vision at this time, according to the institute, but treatment can slow vision loss.
Previous studies suggest cholesterol metabolism may play a role in age-related blindness. Build-up of white blood cells that break down cholesterol, called macrophages, is commonly seen in people with macular degeneration. Also, macrophages may cause abnormal blood vessels to grow in the eye, causing bleeding, scarring and eventually blindness, according to the researchers.
For the new study, published April 2 in Cell Metabolism, researchers took macrophages from old mice and humans with macular degeneration, and saw they had low levels of ABCA1, a protein that transports cholesterol out of cells. That may be what causes the build-up of macrophages seen with the disease. The researchers then tried to activate receptors that would affect ABCA1 expression in mice, with the help of cholesterol-lowering drugs.
They tested two types of drugs named for the cholesterol regulators they target: one called a Liver X Receptor (LXR) agonist in the form of eye drops and injections, and one called a microRNA-33 inhibitor, in the form of an injection.
They found the drugs increased ABCA1 levels and improved cholesterol transport in macrophages, thereby reducing the growth of new blood vessels. The LXR eye drop formulation may cause fewer side effects, the researchers said.
"Our increased understanding of cholesterol's role in the growth of ocular blood vessels helped us identify therapeutically modifiable pathways, opening up avenues for new treatments that may help us prevent blindness caused by macular degeneration," senior study author Dr. Rajendra Apte, a professor of ophthalmology and visual sciences at the Washington University School of Medicine in St. Louis, said in a statement.
He told The Telegraph that the findings could have significant implications at doctors' offices, because researchers may be able to modify drugs that area already available to deliver treatments to the eye.
"Clearly this research is still at an early stage but it will be exciting to watch how it progresses and at some point cholesterol-lowering eye drops may become part of a growing army of treatments for sight-threatening eye conditions," Clara Eaglen, a spokesperson for the U.K. eye charity RNIB who was not involved in the research, told the BBC.