Nanotechnology May Herald Breakthrough Treatment for Aging-Related Vision Loss

Both dry age-related macular degeneration and retinitis pigmentosa are caused by neuroinflammation, which progressively damages the retina and can lead to blindness. Macular degeneration is the primary cause of vision loss in older Americans, affecting more than 7 million people, and retinitis pigmentosa affects 1 in 4,000 Americans; presently there is no cure for either of these diseases.  A collaborative research study among investigators at Wayne State University, the Mayo Clinic and Johns Hopkins Medicine shows that steroids attached to the dendrimers – a type of nanoparticle – targeted the damage-causing cells associated with neuroinflammation, leaving the rest of the eye unaffected and preserving vision. Lead researcher Raymond Iezzi, from Mayo Clinic (Minnesota, USA), explains the team’ study tested the dendrimer delivery system in rats that develop neuroinflammation leading to retinal degeneration. The target was activated microglial cells, the immune cells in charge of cleaning up dead and dying material in the eye. When activated, these cells cause damage via neuroinflammation — a hallmark of each disease.  Dendrimers are tree-like, non-cytotoxic polymeric drug delivery vehicles (~ 4 nm). Surprisingly, the activated microglia in the degenerating retina appeared to eat the dendrimer selectively and retain them for at least a month. The drug is released from the dendrimer in a sustained fashion inside these cells, offering targeted neuroprotection to the retina.  The treatment reduced neuroinflammation in the rat model and protected vision by preventing injury to photoreceptors in the retina. Although the steroid offers only temporary protection, the treatment as a whole provides sustained relief from neuroinflammation.