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Demonstration of AA-protein in formalin-fixed, paraffin-embedded tissues
Abstract:
AA-protein was identified by SDS-acrylamide electrophoresis in amyloid fibrils fixed in formalin after isolation from fresh-frozen tissues obtained from patients with familial Mediterranean fever (FMF) amyloidosis and idiopathic AA-amyloidosis and, following deparaffination, rehydration and homogenization of embedded formalin-fixed tissues of old autopsy cases of the hereditary amyloidosis of FMF and amyloidosis acquired in association with tuberculosis, bronchiectasis, and rheumatoid arthritis. That AA-protein is unaltered by formalin was firmly established by agar gel diffusion using specific rabbit anti-AA serum. By contrast, AL proteins could not be demonstrated either in formalin-fixed amyloid fibrils derived from fresh-frozen tissues of a patient with presumably AL-amyloidosis dominated by cardiomegaly and one with AL-kappa amyloidosis or in blocks of cases of familial neuropathic amyloidosis, multiple myeloma, and idiopathic amyloidosis with cardiopathy. AA-protein is not denatured by formalin and retains its typical electrophoretic, chromatographic, and immunologic characteristics even 30 years after fixation and paraffin-embedding.
Insights
Formalin fixation preserves AA-protein in amyloid fibrils, allowing for reliable identification in archival tissues. This method confirms AA-protein
Area of Science:
- Biochemistry
- Pathology
- Immunology
Background:
- Amyloidosis is a group of diseases characterized by the deposition of amyloid fibrils.
- Distinguishing between different types of amyloidosis, such as AA and AL, is crucial for diagnosis and treatment.
- Formalin fixation is a common method for preserving biological tissues but can potentially alter protein structures.
Purpose of the Study:
- To determine if formalin fixation affects the identification of AA-protein in amyloid fibrils.
- To assess the stability of AA-protein in formalin-fixed and paraffin-embedded tissues over time.
- To investigate the feasibility of detecting AL proteins in formalin-fixed tissues.
Main Methods:
- SDS-acrylamide electrophoresis was used to identify AA-protein in amyloid fibrils from fresh-frozen and formalin-fixed tissues.
- Agar gel diffusion with specific anti-AA serum was employed to confirm the integrity of AA-protein.
- Formalin-fixed tissues from various amyloidosis cases (FMF, idiopathic, hereditary, tuberculosis-associated, rheumatoid arthritis-associated) were analyzed.
- AL proteins were investigated in formalin-fixed tissues from patients with presumed AL-amyloidosis, familial neuropathic amyloidosis, multiple myeloma, and idiopathic amyloidosis with cardiopathy.
Main Results:
- AA-protein was successfully identified in formalin-fixed amyloid fibrils using SDS-PAGE.
- Agar gel diffusion confirmed that AA-protein remains unaltered by formalin fixation.
- Formalin fixation did not denature AA-protein, preserving its electrophoretic, chromatographic, and immunologic characteristics.
- AL proteins could not be demonstrated in the analyzed formalin-fixed tissues.
- AA-protein integrity was maintained in tissues fixed up to 30 years prior.
Conclusions:
- Formalin fixation is a suitable method for preserving AA-protein in amyloid fibrils for diagnostic purposes.
- Archival formalin-fixed tissues can be reliably used to study AA-amyloidosis.
- The study highlights the stability of AA-protein, even in long-term stored samples.