Microtubule alterations may destabilize photoreceptor integrity age-related microtubule changes and pattern of expression of MAP-2, Tau and hyperphosphorylated Tau in aging human photoreceptor cells.

This study examined photoreceptor cell ultrastructure from 18 human donor retinas (32 eyes; age: 45-94 years) and quantified the photoreceptors with altered microtubules over six to ninth decades in four defined retinal regions. In addition, immunoreactivity (IR) to microtubule-associated protein-2 (MAP-2), tau and hyperphophorylated tau was performed in retinal sections from companion eyes. In young donor retinas below 75 years of age, microtubules appeared straight in photoreceptor inner segments and axons. With age, they appeared bent or misaligned in macular and mid-peripheral photoreceptors. In addition, dense granular materials were present in photoreceptor axons and synaptic terminals in advanced ages. In all decades, rod microtubules were affected more than their cone counterparts (28% vs 15%, p < 0.005). Both rods and cones were significantly affected in mid-peripheral retina (5-8 mm outside the macular border) in eighth decade, compared to other decades or retinal regions (parafoveal, perifoveal and nasal) examined (p < 0.005). IR showed a steady expression of MAP-2 in inner segments, and tau in inner segments to axons below 75 years of age, but was absent for both markers in scattered macular and mid-peripheral photoreceptors in advanced ages (>75 years). IR to hyperphosphorylated tau was present mainly in inner retina and increased with aging. Markers of oxidative stress, e.g., lipid peroxidation (4-hydroxy 2-nonenal) and nitrosative stress (nit...

Source: Experimental Eye Research - July 21, 2020 Category: Opthalmology Authors: Nag TC, Kathpalia P, Wadhwa S Tags: Exp Eye Res Source Type: research