To standardize the use of cerebrospinal fluid (CSF) for biomarker research, a set of stability studies have been performed on porcine samples to investigate the influence of common sample handling procedures on proteins, peptides, metabolites and free amino acids. This study focuses at the effect on proteins and peptides, analyzed by applying label-free quantitation using microfluidics nanoscale liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (chipLC-MS) as well as matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FT-ICR-MS) and Orbitrap LC-MS/MS to trypsin-digested CSF samples. The factors assessed were a 30 or 120 min time delay at room temperature before storage at -80 degrees C after the collection of CSF in order to mimic potential delays in the clinic (delayed storage), storage at 4 degrees C after trypsin digestion to mimic the time that samples remain in the cooled autosampler of the analyzer, and repeated freeze-thaw cycles to mimic storage and handling procedures in the laboratory. The delayed storage factor was also analyzed by gas chromatography mass spectrometry (GC-MS) and liquid chromatography mass spectrometry (LC-MS) for changes of metabolites and free amino acids, respectively. Our results show that repeated freeze/thawing introduced changes in transthyretin peptide levels. The trypsin digested samples left at 4 degrees C in the autosampler showed a time-dependent decrease of peak areas for peptides from prostaglandin D-synthase and serotransferrin. Delayed storage of CSF led to changes in prostaglandin D-synthase derived peptides as well as to increased levels of certain amino acids and metabolites. The changes of metabolites, amino acids and proteins in the delayed storage study appear to be related to remaining white blood cells. Our recommendations are to centrifuge CSF samples immediately after collection to remove white blood cells, aliquot, and then snap-freeze the supernatant in liquid nitrogen for storage at -80 degrees C. Preferably samples should not be left in the autosampler for more than 24 h and freeze/thaw cycles should be avoided if at all possible.
A total of 164 cerebrospinal fluid (CSF) samples taken from neurological patients were classed into four groups according to the clinical diagnosis: multiple sclerosis (MScl, n = 44), clinically isolated syndrome of demyelination (CIS, n = 40), other inflammatory neurological disease (OIND, n = 26) and other neurological disease (OND, n = 54). After tryptic digestion, the samples were measured by MALDI-TOF MS. Spectra were analyzed using the R-project software package, in which a peak detection algorithm was developed. Subsequently, the peak lists were compared based on ranked data (non-parametric). Significant differences were observed in the comparisons of MScl vs. OND and CIS vs. OND. The comparisons of MScl vs. OIND, and CIS vs. OIND showed fewer significant differences. No significant differences were found in comparisons MScl vs. CIS and OIND vs. OND. MScl and CIS had strikingly similar profiles, probably a reflection of common pathological mechanisms. Three differentially expressed proteins in the comparison of MScl vs. OND were identified: chromogranin A, a potential marker for neurodegeneration; and two important factors in complement-mediated inflammatory reaction, clusterin and complement C3. CSF chromogranin A levels were confirmed to be significantly elevated in the MScl group using an ELISA.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.