Conclusion:

1. SYNOVIAL TISSUE TRANSCRIPTOME AND SYNOVIAL FLUID PROTEOME HAVE STRONGER DISCRIMINATORY POWER THAN SERUM IN DISSECTING INFLAMMATION IN RHEUMATOID ARTHRITIS Biljana Smiljanovic1, Bruno Stuhlmüller1, Silvial Pade1, Marina Backhaus1, Gerd R. Burmester1, Andreas Radbruch2, Andreas Grützkau2, Thomas Häupl1 1Department of Rheumatology and Clinical Immunology, Charité University Hospital, Berlin, Germany 2DeutschesRheuma – Forschungszentrum, Berlin, Germany Background: Rheumatoid arthritis (RA) is a chronicdiseaseassociatedwithpolyarticularinflammation, cartilageand/orbonedestruction. Currentdiagnosisof RA isbased on clinicalcriteriaandmeasurementof non-specificmarkersofinflammation in theblood. A mainchallenge in diagnosisof RA istoestablishobjectivecriteriaabletoprovide a moredetailedinsightintojointpathobiology. In searchforconvenientbiomarkers, gene-expression profilesfromsynovialtissuesof RA andosteoarthritis (OA) patientsweregenerated. These profileswereusedforselectionofcandidatebiomarkersthatweremeasuredattheproteinlevelboth in synovial fluid andmatchedserumsamplesfrom RA and OA patients. Results: Transcriptome generated form synovial tissues biopsies clearly discriminated RA from OA patients Synovial tissue biopsies from 10 RA and 10 OA patients were used for transcriptome analyses. In total, 2019 Affymetrix IDs (~1500 genes) were differentially expressed including genes involved in: Chemotaxix, Cell adhesion, Extracellular matrix formation. Out of 2019 Affymetrix IDs, 20 top candidate genes were selected for validation at the protein level, including: (1) Cytokines: IL8, CCL2, CXCL9, CXCL10, CXCL13, CCL18 (2) Soluble surface molecules: CD14, CD163, CD44, ICAM1, VCAM1 (3) Proteoliticalenzymes and their inhibitors: MMP1, MMP3, A1AT SYNOVIAL TISSUE TRANSCRIPTOME (2019 AFFYMETRIX IDS) 20 TOP CANDIDATE GENES SELECTED FROM TRANSCRIPTOME Criteria for selection of top candidates: high signal value (high mRNA level) 2. changes in >60% of pair-wise comparisons 3. high fold change IL8 CCL18 CXCL13 CXCL10 ICAM1 MMP1 MMP3 10 RA patients 10 OA patients 10 RA patients 10 OA patients From synovial tissue transcriptome to validation at the protein level in synovial fluid and serum 2.1. CXCL13 and CCL18 as potential markers that discriminated RA from OA were measured in Synovial fluid and Serum SYNOVIAL FLUID (SF) SERUM CCL18 CXCL13 CXCL13 CCL18 **p=0.0016 ***p<0.0001 *p=0.0190 ***p<0.0001 p=0.4928 *p=0.0249 p=0.0806 ***p<0.0001 2.2. 10 molecules as potential pattern that discriminated RA from OA were measured in synovial fluid and serum: CXCL13, CCL18, sCD14, sCD163, sCD44, uPAR, sICAM1, sVCAM1, sE-Sele, sP-Sele (A) The pattern of 10 potential markers measured in SF differentiated RA from OA, with few exceptions (B) The discriminatory power of the pattern of 10 potential markers was weaker in serum compared to SF (C) sE-Sele and sP-Sele measured in SF showed the best correlation with DAS28. However, this correlation was not evident in serum. In contrast, CXCL13 followed by sCD14 and CCL18 correlated with DAS28, both when measured in SF and serum (A) THE PATTERN OF 10 MARKERS IN SYNOVIAL FLUID (SF) (C) CORRELATION OF 10 MARKERS MEASURED IN SF AND SERUM WITH CLINICAL DATA Corr scale 10 RA patients 11 OA patients (B) THE PATTERN OF 10 MARKERS IN SERUM 10 RA patients 11 OA patients Healthydonors (ND) Conclusion: Disease-specificprofileswere evident in thejointwherebothsynovialtissuetranscriptsandrelated SF proteinsrevealed a cleardifferencesbetween RA and OA. Despitebloodis a favourablediagnostic material, theresultsfromthisstudyindicatedthatthecapacityofbloodtodiluteandneutraliseinflammationis robust enoughtolimitdiscriminationbetween RA and OA. Materials and Methods : Gene-expression profilesfromsynovialtissuesbiopsisweregeneratedbyAffymetrixHG-U133A arrays. The BioRetisdatabase was usedforarrayanalyses. ELISA and multiplex immunoassayswereusedforvalidationofthemarkersattheproteinlevel. Biljana Smiljanovic Department ofRheumatologyandClinical Immunology, Charité University Hospital Charitéplatz 1 D-10117 Berlin Germany E-Mail: smiljanovic@drfz.de Funding: BTCurecontractno 115142-2 ArthroMarkgrantno 01EC1009A