Impact of heat-induced retrieval methods on silver staining for detecting senile plaques of Alzheimer's disease in human brain tissue sections

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• Picked for Histology (top studies of the week, 8 November 2026): Compares retrieval and silver-staining methods in preserved tissue

Abstract

BACKGROUND: Silver staining continues to serve as a critical technique for histological detection of pathological deposits, especially in the context of Alzheimer's disease (AD). In clinical research, paraffin-embedded sections are often stored for extended periods, and tissues may remain in formaldehyde for prolonged durations, both of which can lead to false-negative results. The objective of this study was to systematically evaluate whether heat-induced retrieval can enhance the efficacy and sensitivity of classical silver staining in these suboptimally preserved brain tissues. METHODS: This study investigated the impact of heat-induced retrieval methods on silver staining efficacy in brain tissue. Three types of samples were examined: standard FFPE sections, tissues immersed in formaldehyde for 48 months, and paraffin‑embedded sections (initially fixed for 48 h in formalin, sections coated with paraffin and stored on slides) stored for seven years. Retrieval methods were performed using citrate-citric acid buffer, Tris-EDTA buffer, or proteinase K. Silver staining was conducted using three classical methods: Bielschowsky, periodic acid-methenamine silver (PAM), and Gallyas; untreated sections were used as controls. RESULTS: Results showed that both citrate-citric acid and Tris-EDTA significantly increased the signal-to-noise ratio of senile plaques in Bielschowsky staining. This improvement facilitated better the detection of amyloid plaque details and density, with Tris-EDTA yielding higher sensitivity in long-stored paraffin sections. Proteinase K digestion did not enhance Bielschowsky staining results. None of the retrieval methods improved signal-to-noise ratio for senile plaques or neurofibrillary tangles with PAM or Gallyas. CONCLUSIONS: These findings indicate that heat-induced retrieval methods with citrate or Tris-EDTA buffer, enabling more efficient silver ion reduction at specific targets in Bielschowsky. This work provides an experimental basis for optimizing silver staining protocols, which helps enhance diagnostic accuracy in neuropathological studies of AD and related disorders.

Abstract as published, via PubMed.