Little is known about the mechanisms of the most common form of age-related macular degeneration (AMD), “dry” AMD. Now animal studies by scientists from France, Italy, and Canada suggest that deficiency of a receptor that is normally expressed in the retina results in key features of dry AMD (Houssier M et al. PLoS Med. 2008;5:e39).
CD36 is a “scavenger” receptor that is involved in phagocytosis of worn-out photoreceptor outer segments (the part of the photoreceptor that absorbs light), a process critical for the long-term maintenance of the retina. The researchers found that as rodents lacking CD36 aged, they developed retinal degeneration and choroidal involution, or shrinkage. The investigators also found that CD36 deficiency prevents the induction of cyclooxygenase 2, which controls expression of vascular endothelial growth factor, a protein that stimulates blood vessel growth and is needed for normal choroidal development.