RESUMO
Amyloidosis is a disease characterized by local and systemic extracellular deposition of amyloid protein fibrils where its excessive accumulation in tissues and resistance to degradation can lead to organ failure. Diagnosis is challenging because of approximately 36 different amyloid protein subtypes. Imaging methods like immunohistochemistry and the use of Congo red staining of amyloid proteins for laser capture microdissection combined with liquid chromatography tandem mass spectrometry (LMD/LC-MS/MS) are two diagnostic methods currently used depending on the expertise of the pathology laboratory. Here, we demonstrate a streamlined in situ amyloid peptide spatial mapping by Matrix Assisted Laser Desorption Ionization-Mass Spectrometry Imaging (MALDI-MSI) combined with Trapped Ion Mobility Spectrometry for potential transthyretin (ATTR) amyloidosis subtyping. While we utilized the standard LMD/LC-MS/MS workflow for amyloid subtyping of 31 specimens from different organs, we also evaluated the potential introduction in the MS workflow variations in data acquisition parameters like dynamic exclusion, or testing Data Dependent Acquisition combined with High-Field Asymmetric Waveform Ion Mobility Spectrometry (DDA FAIMS) versus Data Independent Acquisition (DIA) for enhanced amyloid protein identification at shorter acquisition times. We also demonstrate the use of Mascot's Error Tolerant Search and PEAKS de novo sequencing for the sequence variant analysis of amyloidosis specimens.
RESUMO
Plasma renin activity (PRA) is essential for the screening and diagnosis of primary aldosteronism (PA), a form of secondary hypertension, which affects approximately 100 million people worldwide. It is commonly determined by radioimmunoassay (RIA) and, more recently, by relatively low-throughput LC-MS/MS methods. In order to circumvent the negative aspects of RIAs (radioisotopes, cross-reactivity) and the low throughput of LC-MS based methods, we have developed a high-throughput immuno-MALDI (iMALDI)-based assay for PRA determination using an Agilent Bravo for automated liquid handling and a Bruker Microflex LRF instrument for MALDI analysis, with the goal of implementing the assay in clinical laboratories. The current assay allows PRA determination of 29 patient samples (192 immuno-captures), within ~6 to 7h, using a 3-hour Ang I generation period, at a 7.5-fold faster analysis time than LC-MS/MS. The assay is performed on 350µL of plasma, and has a linear range from 0.08 to 5.3ng/L/s in the reflector mode, and 0.04 to 5.3ng/L/s in the linear mode. The analytical precision is 2.0 to 9.7% CV in the reflector mode, and 1.5 to 14.3% CV in the linear mode. A method comparison to a clinically employed LC-MS/MS assay for PRA determination showed excellent correlation within the linear range, with an R(2) value of ≥0.98. This automated high throughput iMALDI platform has clinically suitable sensitivity, precision, linear range, and correlation with the standard method for PRA determination. Furthermore, the developed workflow based on the iMALDI technology can be used for the determination of other proteomic biomarkers. This article is part of a Special Issue entitled: Medical Proteomics.
