AB0157 SYNOVIAL FLUID PROTEOMICS IN PATIENTS WITH ANKYLOSING SPONDYLITIS

Abstract

Background Ankylosing Spondylitis (AS), affecting 0.5% of the population, is a chronic inflammatory rheumatic disease affecting the axial skeleton and peripheral joints. When peripheral arthritis in ankylosing spondylitis (AS) develops early in the disease course it is a predictor of more aggressive disease. SF is in contact with the primary tissues affected by arthritic diseases and has been implicated in disease pathophysiology. Therefore it is an excellent source for discovery of biomarkers. Objectives We used proteomic analysis using SFs from AS patients and other arthritis patients in order to discover novel diagnostic markers for AS. Our aim was to identify differentially expressed protein mediators in synovial fluid of ankylosing spondylitis. Methods A Total of 40 SF samples from 10 AS and each 10 controls [Osteoarthritis (OA), Rheumatoid Arthritis (RA), gouty arthritis (Gout)] were collected. Liquid chromatography and tandem mass spectrometry (LC-MS/MS), to identify differentially expressed proteins based on the ratios of the extracted ion current of each protein between the four groups. Among the 9 proteins showing 1.5 fold change, 8 were verified with the exception of the abundant protein Haptoglobin (HP). Matrix metalloproteinase-1(MMP1) and Matrix metalloproteinase-3(MMP3) were used as a positive control, and the remaining 6 proteins were subjected to western blot analysis. Results We identified 9 proteins that were found to be more than 1.5-fold differentially expressed in SF of AS patients compared to control groups. Proteins such as HP, MMP1, MMP3, Serum amyloid P-component(APCS), Complement factor H-related protein 5(CFHR5), Fumarylacetoacetase(FAH), Mannose-binding lectin2(MBL2), Complement component C9(C9) and Complement C4-A(C4A) were found to be upregulated in the SF of AS patients. CFHR5 and C9 were reported in previous studies with AS serum. APCS was reported in SF as well as serum. However, FAH, C4A and MBL2 were newly discovered through this analysis. We were able to verify the unique expression level of C9 and CFHR5 in AS sample using western blot analysis compared to the other three diseases. Conclusion We performed quantitatively proteomic profiling of the respective SF sample from 4 diseases, i.e., AS, OA, RA, and GOUT, by LC-MS/MS. The systematic comparative proteomic analysis of the four groups together was carried out for the first time, leading to several differentially expressed proteins in AS. Among them, we expect C9 and CFHR5, which expression levels were confirmed by western blot analysis, can be a potential biomarker for AS.