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

<b>Objective</b>: 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. <b>Materials and Methods</b>: 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. <b>Results</b>: 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. <b>Conclusion</b>: 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.