Proteomic analysis of serum-derived extracellular vesicles in ankylosing spondylitis patients.

Background: Ankylosing spondylitis (AS) is a chronic inflammatory disease, whose pathogenesis is still unclear. Many studies show the proteins in extracellular vesicle (EVs) would change regularly in many diseases. The study aims to explore the proteins contents of serum-derived EVs in AS patients.

Methods: EVs were separated by ExoQuick kit. The protein profiles of AS patients and healthy subjects were analyzed by Label-free-liquid chromatography mass spectrometry (LC-MS/MS) technology. Enzyme-linked immunosorbent assay (ELISA) was used to verify the levels of the differently expressed proteins. Receiver operation characteristic (ROC) curves and bioinformatic analysis were conducted.

Results: Six hundred and ten serum-derived EVs proteins from AS patients were detected. Seventy-three diferentially expressed proteins were found in AS group, compared with healthy subjects. Of these, 31 proteins were up-regulated in AS group, while 42 proteins were down-regulated. ELISA result showed that EVs-derived serum amyloid A-1 (SAA1) was higher in AS group, which was consistent with the Label-free-LC-MS/MS data. ROC curves result revealed that the area under curve (AUC) value of EVs-derived SAA1 for AS was 0.768 (0.652-0.885). Bioinformatic analysis revealed that the differently expressed proteins in AS group were significantly involved in "complement and coagulation cascades", "staphylococcus aureus infection", "systemic lupus erythematosus" and "PI3K-Akt signaling pathway".

Conclusions: The protein profiles of serum-derived EVs in AS patients and healthy subjects were different. EVs-derived SAA1 may be a potential biomarkes of AS. The function analysis indicated that the differentially expressed proteins may potentially participate in immune response.