# Robust immunohistochemical detection of α-synuclein, tau and amyloid-β in human brain tissue archived for up to 78 years

## TL;DR

Old brain tissue stored for up to 78 years can still be used to detect key proteins linked to neurodegenerative diseases like Alzheimer's and Parkinson's.

## Contribution

Demonstrates that archival brain tissue remains viable for immunohistochemical analysis of α-synuclein, tau, and amyloid-β.

## Key findings

- Original paraffin blocks showed consistent staining for α-synuclein, tau, and amyloid-β.
- Newly prepared blocks had slightly lower scores for α-synuclein and tau but remained largely usable.
- Amyloid-β staining was stable or slightly improved in newly prepared blocks.

## Abstract

Objective: Brain branks preserve extensive material relevant to
neurodegenerative disease research. As these collections age, tissue becomes
archival, raising the question of whether long-term fixed and stored human brain
tissue remains suitable for contemporary immunohistochemical analyses.

Materials and Methods: Forty-one autopsy brains collected between
1946 to 1980 were examined. For each case, midbrain and hippocampus were
available both as original paraffin-embedded blocks and as tissue stored long
term in fixative. New paraffin blocks were prepared from the long-term fixated
tissue. Sections from original and newly prepared blocks were
immunohistochemically stained for α-synuclein, hyperphosphorylated tau and
amyloid-β. Immunoreactivity was assessed using semi-quantitative
scoring.

Results: Original blocks consistently showed good staining intensity
and morphological preservation for each protein pathology. Newly prepared blocks
showed slightly lower semi-quantitative scores for Lewy-related pathology,
without statistically significant differences, except for astrocytic
α-synuclein in the substantia nigra in cases from the 1960s. Tau pathology
displayed modestly reduced labelling, particularly of the neuropil threads and
neurofibrillary tangles, most evident in cases from the 1950s.
Amyloid-β-positive senile plaques showed similar or slightly higher scores
in newly prepared blocks, with no significant differences across regions.

Conclusion: Human brain tissue preserved as paraffin-embedded blocks
or stored in fixative for up to 78 years remains suitable for
immunohistochemical analyses. Adequate-to-good detection of aggregated
α-synuclein, hyperphosphorylated tau and amyloid-β is achievable,
indicating preserved pathological hallmarks of Lewy Body Disease and Alzheimer’s
Disease in archival tissue.