Elevated ITGAX/CD11c in CSF-Derived Extracellular Vesicles Reflects Disability Progression in Multiple Sclerosis

BACKGROUND AND OBJECTIVES: Extracellular vesicles (EVs) are membrane-bound particles that are released into the extracellular space and are believed to play a role in the pathogenesis of neuroinflammation and neurodegeneration. Nevertheless, the precise role of these vesicles in the context of multiple sclerosis (MS) remains uncertain. The objective of this study was to identify the distinctive characteristics of EVs associated with MS. METHODS: EVs were isolated from CSF using phosphatidylserine affinity methods. Mass spectrometry was used to analyze CSF samples and EVs isolated from those CSF samples collected from a discovery cohort of 10 patients with other neurologic diseases (ONDs) and 10 patients with MS. In addition, mass spectrometry was used to analyze EVs isolated from CSF samples in a validation cohort of 24 patients with ONDs, 38 patients with MS, and 14 patients with neuromyelitis optica spectrum disorders. RESULTS: The results revealed notable increases in the levels of 33 proteins in the CSF samples and 100 proteins in the CSF-derived EVs from patients with MS in the validation cohort. Increases in the levels of ITGA4, ITGAX (CD11c), MS4A1 (CD20), CD3E, CD4, and CD8A, which are marker proteins of lymphocytes and myeloid cells, including activated microglia and dendritic cells, were observed in the CSF-derived EVs in the discovery cohort. The results of the validation cohort revealed that the levels of 4 proteins, ITGA4, ITGAX, MS4A1, and CD3E, were significantly greater in patients with MS than in patients with ONDs. Furthermore, the level of ITGAX was greater in the patients with confirmed disability worsening (CDW) than in those without CDW. The results of the receiver operating characteristic (ROC) and Kaplan-Meier analyses indicated that ITGAX levels in CSF-derived EVs may prove useful in predicting disease prognosis. DISCUSSION: Our findings suggest that CSF-derived EVs reflect immunologic changes in MS and other neuroimmune diseases. In addition, these results raise the possibility that changing in myeloid cells and lymphocytes may also play a role in the pathogenesis of MS. CSF-derived EVs may serve as indicators of MS disease severity and could be used as biomarkers in the future.