Targeted Mass Spectrometry-Based Assays for Relative Quantification of 30 Brain-Related Proteins and Their Clinical Applications

Cerebrospinal
fluid (CSF) is a promising clinical sample for identification
of novel biomarkers for various neurological disorders. Considering
its direct contact with brain tissue, CSF represents a valuable source
of brain-related and brain-specific proteins. Multiple sclerosis is
an inflammatory, demyelinating neurological disease affecting the
central nervous system, and so far there are no diagnostic or prognostic
disease specific biomarkers available in the clinic. The primary aim
of the present study was to develop a targeted mass spectrometry assay
for simultaneous quantification of 30 brain-related proteins in CSF
and subsequently to demonstrate assay feasibility in neurological
samples derived from multiple sclerosis patients. Our multiplex selected
reaction monitoring assay had wide dynamic range (median fold range
across peptides = 8.16 × 103) and high assay reproducibility
(median across peptides CV = 4%). Candidate biomarkers were quantified
in CSF samples from neurologically healthy individuals (n = 9) and
patients diagnosed with clinically isolated syndrome (n = 29) or early
multiple sclerosis (n = 15).