Subtyping of cardiac amyloidosis by mass spectrometry-based proteomics of endomyocardial biopsies

Abstract

Background

Cardiac amyloidosis is a severe condition leading to restrictive cardiomyopathy and heart failure. Mass spectrometry-based methods for cardiac amyloid subtyping have become important diagnostic tools but are currently used only in a few reference laboratories. Such methods include laser-capture microdissection to ensure the specific analysis of amyloid deposits. Here we introduce a direct proteomics-based method for subtyping of cardiac amyloidosis.

Methods

Endomyocardial biopsies were retrospectively analysed from fresh frozen material of 78 patients with cardiac amyloidosis and from 12 biopsies of unused donor heart explants. Cryostat sections were digested with trypsin and analysed with liquid chromatography - mass spectrometry, and data were evaluated by proteomic software.

Results

With a diagnostic threshold set to 70% for each of the four most common amyloid proteins affecting the heart (LC κ, LC λ, TTR and SAA), 65 of the cases (87%) could be diagnosed, and of these, 61 cases (94%) were in concordance with the original diagnoses. The specimens were also analysed for the summed intensities of the amyloid signature proteins (ApoE, ApoA-IV and SAP). The intensities were significantly higher (p < 0.001) for all assigned cases compared with controls.

Conclusion

Cardiac amyloidosis can be successfully subtyped without the prior enrichment of amyloid deposits with laser microdissection.

Keywords:

• Cardiac amyloidosis
• endomyocardial biopsies
• mass spectrometry
• proteomics
• subtyping

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This study was supported by grants from the Swedish Research Council (No 2021-02109 to AO), the Swedish Heart-Lung Foundation (No 20210230 to AO) and the Swedish State Support for Clinical Research (ALFGBG-978196 to AO, ALFGBG-966234 to GL and strategic funding for MS instrumentation). We would also like to acknowledge Britt-Marie Olsson for sample preparation and staff at the Proteomics Core Facility at Sahlgrenska Academy for assistance with MS analyses.