SAT0055 JOINT SPECIFIC TNF RESPONSE OF SYNOVIAL FIBROBLASTS IN RHEUMATOID ARTHRITIS
Authors: Raphael Micheroli, Amanda Mcgovern, Kerstin Klein, Xiangyu Ge, Paul Martin, Oliver Distler, Mojca Frank-Bertoncelj, Stephen Eyre, Caroline Ospelt
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Synovial fibroblasts (SF) in rheumatoid arthritis (RA) play a major role in chronic inflammation and joint destruction. We showed previously that their epigenetic and transcriptional profile as well as their function vary significantly between different joints. However, it is unknown whether there is a joint-specific inflammatory response of SF. <h3>Objectives:</h3> To compare transcriptional changes between SF from hand, shoulder and knee joints after stimulation with the pro-inflammatory cytokine TNF. <h3>Methods:</h3> We cultured SF from synovial tissues of hand (metacarpophalangeal and proximal interphalangeal joint), shoulder and knee joints of RA patients. After stimulation of the SF with 10 ng/ul TNF for 24h (n=2 for each joint location), RNA was sequenced on the Illumina HiSeq4000 platform. We analyzed differential gene expression with R v3.5.2 and CuffDiff and DESeq2 packages. <h3>Results:</h3> As shown in Figure 1, principal component analysis showed evident separation of joint locations and condition (unstimulated vs TNF stimulated). In a sample-to-sample distance matrix, hand samples (TNF stimulated and unstimulated) grouped apart from shoulder and knee samples (Figure 2). Of the regulated genes, 26% appeared in all three joint locations and 56% overlapped between knee and shoulder, but only 30% overlapped between hand and shoulder and between hand and knee SF. Similarly, also enriched pathways differed particularly between hands and the more proximal joints. 'Defense response' (p=8.11×10<sup>-23</sup>) and 'cytokine activity' (p=1.27×10<sup>-21</sup>) were the most significantly enriched gene ontology terms for genes regulated in TNF stimulated hand SF. These processes were less prominently enriched in stimulated knee (1.58x10<sup>-15</sup> and 8.84x 10<sup>-08</sup>) and shoulder SF (2.02x10<sup>-11</sup> and 3.20x10<sup>-07</sup>), where 'cell cycle' (p=2.26×10<sup>-30</sup> in knee and p=2.18×10<sup>-32</sup> in shoulder), and 'DNA packaging complex' (p=4.63×10<sup>-49</sup> in knee and p=8.91×10<sup>-36</sup> in shoulder) were the most significantly enriched gene ontology terms. These processes were not significantly enriched in stimulated hand SF. <h3>Conclusion:</h3> SF from different joints in RA react differently to TNF stimulation. In particular hand SF reacted different to TNF stimulation than shoulder and knee SF, which appeared more similar. These qualitative and quantitative differences of the inflammatory response might translate into joint-specific pathotypes of synovitis with distinct therapeutic responses and disease outcomes. <h3>Acknowledgement:</h3> This work was supported by the Institute for Rheumatic Research (IRR), Epalinges, Switzerland. <h3>Disclosure of Interests:</h3> Raphael Micheroli: None declared, Amanda McGovern: None declared, Kerstin Klein: None declared, Xiangyu Ge: None declared, Paul Martin: None declared, Oliver Distler Grant/research support from: Prof. Distler received research funding from Actelion, Bayer, Boehringer Ingelheim and Mitsubishi Tanabe to investigate potential treatments of scleroderma and its complications, Consultant for: Prof. Distler has/had consultancy relationship within the last 3 years with Actelion, AnaMar, Bayer, Boehringer Ingelheim, ChemomAb, espeRare foundation, Genentech/Roche, GSK, Inventiva, Italfarmaco, iQvia, Lilly, medac, MedImmune, Mitsubishi Tanabe Pharma, Pharmacyclics, Novartis, Pfizer, Sanofi, Serodapharm and UCB in the area of potential treatments of scleroderma and its complications. In addition, he had/has consultancy relationship within the last 3 years with A. Menarini, Amgen, Abbvie, GSK, Mepha, MSD, Pfizer and UCB in the field of arthritides and related disorders, Mojca Frank-Bertoncelj : None declared, Stephen Eyre: None declared, Caroline Ospelt: None declared