OP0062 MULTI-MODAL ANALYSIS OF SYNOVIAL TISSUE MACROPHAGES INFORMS ON TREATMENT RESPONSE IN NAIVE TO TREATMENT RHEUMATOID ARTHRITIS
Authors: S. Alivernini, S. Perniola, B. Tolusso, A. Elmesmari, M. Gessi, C. DI Mario, L. A. Coletto, M. R. Gigante, L. Petricca, V. A. Pacucci, D. Bruno, D. Somma, L. Macdonald, R. Benvenuto, L. Bui, M. A. D’agostino, E. Gremese, J. Bacardit, M. Kurowska-Stolarska
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Synovial tissue (ST) inflammation in Rheumatoid Arthritis (RA) shows high degree of heterogeneity which may underly variable response to treatments. Novel insights from high-throughput ST analyses showed their potential in dissecting disease heterogeneity and in identifying putative novel biomarkers of prognosis. <h3>Objectives:</h3> To assess the power of multi-modal analysis of ST inflammation in naive to treatment RA to identify predictive biomarkers of treatment response. <h3>Methods:</h3> 373 naive to treatment RA were enrolled and underwent Ultrasound guided ST biopsy. For each patient, synovitis degree was determined using a H&amp;E-based semiquantitative score (Krenn Synovitis Score - KSS)[1] and synovial pathotype was determined using immunohistochemistry. Among those, n=45 ST samples were used for synovial tissue macrophage (STMs)(CD206/MerTK) FACS phenotyping and Digital Spatial Profiling (DSP)(GeoMx DSP, Nanostring) to quantitate abundance and transcriptomic profiles of CD68<sup>pos</sup> cells in 103 spatially distinct ST regions of interest (ROI). After study entry, each RA patient was treated according to the treat to target strategy and was followed every 3 months to assess DAS remission achievement at 6 months follow-up. <h3>Results:</h3> Naive RA who achieved DAS-remission at 6 months follow-up with the treat to target strategy had, at baseline, lower KSS compared to patients not achieving this outcome (p=0.0006). Moreover, naive to treatment RA with lympho-myeloid (LM) as well as diffuse-myeloid (DM) pathotype had lower response rate to cDMARDs (36.1% and 44.7%) compared to RA with pauci-immune (PI) pathotype (59.1%, p=0.001 and p=0.042 respectively). However, SHAP methods showed that baseline KSS has limited individualized prediction capacity between responder and non-responder, highlighting the need for multi-modal tissue deconvolution. At FACS analysis, patients with DM and LM pathotypes showed comparable enrichment of MerTK<sup>pos</sup>CD206<sup>pos</sup> and MerTK<sup>neg</sup>CD206<sup>neg</sup> STMs populations, while patients with PI pathotype showed an expansion of MerTK<sup>pos</sup>CD206<sup>pos</sup> STMs (p=0.0106). Moreover, naive RA who achieved DAS-remission at 6 months follow-up had higher MerTK<sup>pos</sup>CD206<sup>pos</sup> STMs rates than patients not achieving this clinical outcome (p=0.0002). In particular, baseline MerTK<sup>pos</sup> STMs enrichment ≥44.3% [AUC:0.80 (95% IC:0.65-0.94), p=0.001] arose as an independent factor associated with DAS-remission achievement at 6 months follow-up [OR: 24.5 (95% IC:4.3-139.2), p&lt;0.0001]. DSP analysis of naïve to treatment ST biopsies revealed differential gene networks characterising activation of STMs in distinct tissue locations (e.g. lining layer, sublining layer and intra-follicular structure distribution respectively). Moreover, DSP analysis enabled to identify transcriptomic signatures of lining and sublining STMs associated with treatment response to cDMARDs (e.g. <i>MERTK</i>, <i>KLF4</i>, <i>APP</i>) as well as of treatment refractoriness (e.g. <i>SPP1, S100A12, TNF</i>). Integration of STM scRNAseq dataset[2] with STMs spatial transcriptomic data, successfully mapped all STM clusters in ST stratified based on treatment response, showing an enrichment of S100A12<sup>pos</sup> and SPP1<sup>pos</sup> STMs mainly located in sublining ROIs of naive to treatment RA not responding to cDMARDs. <h3>Conclusion:</h3> Multi-modal analysis of synovitis enables to differentiate, at first medical evaluation, naïve-to-treatment RA who subsequently responded to first line cDMARDs treatment from those who failed, strongly supporting its predictive value as putative patient-based decision test tool. <h3>REFERENCES:</h3> [1] Alivernini S, et al. Arthritis &amp; Rheumatology 2021. [2] Alivernini S, et al. Nat. Medicine 2020. <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>