Abstract
Purpose :
Alzheimer s disease (AD) is characterized by amyloid beta (Aβ) plaques in brain and retina. The ocular manifestation of AD shares similarities with other retinal degenerations, such as diabetic retinopathy or wet AMD. Standardized, unequivocal determination of amyloid precursor protein (APP) and its cleavage products is inevitable for providing new diagnostic and therapeutic approaches. Since the incidence of Aβ plaques in AD retina is controversially discussed, we systematically analyzed brain and retina samples of an AD mouse model (APPSwe/PS1ΔE9) and human dementia post-mortem tissue to optimize protocols for staining of Aβ plaques.
Methods :
Mouse and human brain and retina were analyzed in paraffin and cryosections. Aβ was stained by immunohistochemistry, varying formic acid (FA) pretreatment as well as dilutions and incubation times of three antibodies (Aβ 6E10, 4G8, 1-40/42), or with natural dyes (Congo red, curcumin, thioflavin S). Retinal Aβ staining required higher antibody concentrations. Optimized staining procedures using Aβ 1-40/42 or thioflavin S were then applied to paraffin sections of human dementia brain and retina samples.
Results :
Immunohistochemistry revealed that 70% FA treatment for 10 min is necessary and sufficient for antigen recovery without dissolving plaques. Both equally efficient antibodies 6E10 and 1-40/42 surpassed 4G8. Aβ was located surrounding and within blood vessels. Thioflavin S and curcumin were suitable for identifying Aβ in brain and retina, while Congo red failed to stain retinal plaques. Aβ deposition was detectable in both paraffin and cryosections with retinal morphology best preserved in mouse paraffin sections. The occurrence of Aβ plaques in the human retina was definitively demonstrated.
Conclusions :
Optimized immunohistochemical staining backed-up by natural dyes is effective for unequivocally identifying Aβ plaques in AD tissues. Natural dyes might be considered promising for fast amyloid detection in the retina.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.