Abstract
BACKGROUND: The aim of this study is to explore the quantity profiles of amyloid signature proteins (serum amyloid P component, SAP; apolipoprotein E, ApoE; apolipoprotein A-IV) in common types of renal amyloidosis by mass spectrometry and immunostaining methods. METHODS: Twenty-one patients with renal amyloidosis of different types evaluated at the Renal Pathological Center of Peking University First Hospital from 2000 to 2021 were enrolled. Immunohistochemistry (IHC) and laser microdissection combining with mass spectrometry (LMD-MS) were applied to investigate the localization and quantity profiles of signature proteins in renal amyloidosis. The co-localization relationships among signature proteins and amyloid fibrils, as well as the ultrastructural localization of SAP were examined by laser scanning confocal microscopy (LSCM) and immuno-electron microscopy (IEM), respectively. RESULTS: By MS-based proteomic analysis, large spectra numbers of ApoE and its higher abundance were noted in four types of amyloidosis when compared with SAP, and ApoA-IV was absent in ALECT2 amyloidosis. LSCM showed ApoE and SAP co-localized with amyloid fibrils in renal AL-κ, AL-λ and ALECT2 amyloidosis. ApoA-IV co-localized with amyloid fibrils in AL-κ and AL-λ amyloidosis, but was not found in ALECT2 amyloidosis. By semi-quantitative analysis based on LSCM and IEM, the quantity levels of signature proteins in AL-κ appeared to be lower than that in AL-λ (P < 0.05) or ALECT2 (P < 0.05), while there was no significant difference between AL-λ and ALECT2 amyloidosis. CONCLUSION: Both of SAP and ApoE were the ubiquitous signature components of renal amyloidosis (AL, AA, ALECT2), as well as ApoA-IV in AL and AA, but not in ALECT2. ApoE was the key signature protein in renal amyloidosis. The quantity levels of signature proteins investigated through LCSM/IEM demonstrated variability among different types, with AL-κ amyloidosis appeared to have a lower level. CLINICAL TRIAL NUMBER: Not applicable.