Protein aggregation in the aging retina

The age-related altered expression of neuron-related proteins as seen in other regions of the central nervous system is expected in the aging retina. Using immunohistochemical techniques, we characterized the distribution and aggregation of tau, βA4-amyloid, α-synuclein, and ubiquitin in human retina obtained from 19 enucleated eyes of patients aged 49 to 87 years and correlated the findings with the ages. Using a phosphorylation-independent antibody, tau aggregates were observed within the cytoplasm of several photoreceptor cells, and there was a positive correlation between age and the number of tau-positive ganglionic cells. Tau deposits were immunonegative with a phosphorylation-dependent antibody. We did not observe βA4-amyloid in subretinal pigment epithelium deposits or in neuroepithelial layers. α-Synuclein and ubiquitin inclusions were found in the inner nuclear layer, and there was colocalization of these proteins. The proportion of patients displaying such α-synuclein and/or ubiquitin intracytoplasmic inclusions was significantly higher with aging. The presence of ubiquitin deposits within drusen was remarkable, but diffuse ubiquitin aggregates between the retinal pigment epithelium and Bruch membrane were also noticed. These results indicate that protein aggregation in the retina increases with aging and that tau, α-synuclein, and ubiquitin should be the subjects of future investigations.