Scientists have identified a new target for the diagnosis and treatment of age-related macular degeneration (AMD). AMD most commonly affects people over the age of fifty and is the leading cause of vision loss in those over sixty. The rarer, but more serious form of the disease, wet AMD, is caused by abnormal blood vessel growth under the macula (centre of the retina) and can develop very quickly. Although the condition is painless, the new blood vessels leak blood and fluid which lift the macula and destroy sharp central vision. The condition can be treated with laser surgery, photodynamic therapy or anti-vascular endothelial growth factor (anti-VEGF) injections into the eye, although none of these treatments provides a complete cure and loss of vision may continue despite treatment.
The new study, published online on Jun 14th in Nature, shows that blocking the eosinophil/mast cell chemokine receptor, CCR3, can reduce the abnormal blood vessel growth that leads to AMD. The researchers detected CCR3 protein in eye tissue from people with AMD but not in eye tissue from people of the same age who did not have the disease. In studies in mice, blocking CCR3, either by genetic engineering or using antibodies, reduced the number of abnormal blood vessels. In the mice, targeting CCR3 was shown to be more effective than targeting VEGF (70% vs 60%), suggesting that CCR3 blockers could also provide an effective treatment for patients with AMD. The team injected anti-CCR3 antibodies attached to semiconductor nanocrystals into mice and, using conventional ocular angiography techniques, were able to visualise the abnormal blood vessels even before they had penetrated the retina. Since CCR3 was detected at an early stage in the development of the disease, the researchers hope that the new imaging technology could be used diagnostically, and that early detection will provide better opportunities to prevent structural damage and preserve vision.