Immunoreactivity against tau, amyloid precursor protein, and beta-amyloid in the human retina

Increased immunoreactivity (IR) of beta-amyloid and the amyloid-associated proteins tau and amyloid precursor protein (APP) in the brain have been linked to the pathogenesis of neurodegenerative disorders such as Alzheimer's disease. However, the expression of these proteins has not been investigated in the normal or diseased human retina.

Using immunohistochemical techniques, we examined the distribution and age-related changes of anti-tau-1, anti-tau-2, anti-APP, and anti-beta-amyloid IR in the human retina at various ages (n = 24), in retinitis pigmentosa (RP, n = 6), and in age-related macular degeneration (ARMD, n = 10).

Tau-1 immunoreactivity was intense in the inner retinal layers and did not change with age or in RP. Eyes with ARMD showed less intense staining but exhibited a similar distribution. Tau-2 IR was faint and did not change with age but was mildly increased in the retinal pigment epithelium (RPE) of eyes with RP and in the retina of eyes with ARMD. APP IR was most prominent in the ganglion cell and nerve fiber layer, and it appeared to increase in ganglion cells of older persons and in RPE cells of eyes with RP and ARMD. Beta-amyloid IR was only detected focally in sub-RPE deposits in eyes from older persons.

The proteins investigated in this study are present in the human retina. The staining pattern of tau is different from the brain, but it shows no age-related changes. The increased immunoreactivity of APP in retinal ganglion cells of older eyes and in RPE cells of eyes with RP and ARMD, as well as the patchy staining of beta-amyloid within sub-RPE deposits, might indicate a relationship of these proteins to retinal aging and possibly to retinal degeneration in RP.