Syndecan-1 as specific cerebrospinal fluid biomarker of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease often characterized by remission and relapse periods occurring at irregular intervals after an initial attack (clinically isolated syndrome) and followed by a gradual progression of disability. Clinical symptoms, magnetic resonance imaging and abnormalities in cerebrospinal fluid (CSF) immunoglobulin profile allow diagnosis with a good sensitivity. However, current biomarkers lack specificity or have poor individual prognostic value. To identify novel candidate biomarkers of MS, we analysed 1) the CSF proteome from symptomatic controls and patients with clinically isolated syndrome or remitting-relapsing multiple sclerosis (n=40), and 2) changes in oligodendrocyte secretome upon proinflammatory or pro-apoptotic treatment. Proteins exhibiting differences in abundance in both studies were combined with previously described MS biomarkers to build a list of 87 proteins that were quantified by parallel reaction monitoring (PRM) in CSF samples from a new cohort comprising symptomatic controls and MS patients at different disease stages (n=60). The eleven proteins that passed this qualification step were subjected to a new PRM assay from a larger cohort (n=158) comprising patients with MS at different disease stages or with other inflammatory or non-inflammatory neurological disorders. Collectively, these studies identified a biomarker signature of MS that might improve MS diagnosis and prognosis. These include the oligodendrocyte precursor cell proteoglycan Syndecan-1, which was more efficient than previously described biomarkers to discriminate MS from other inflammatory and non-inflammatory neurological disorders.