CO:07:5 | Enhanced fibroblast signatures in females with early rheumatoid arthritis highlights a potential basis for poorer treatment outcomes

Benedetta Monosi¹, James Perera², Alessandra Nerviani^2|3, Maria Sole Chimenti¹, Felice Rivellese^2|3, Costantino Pitzalis^2|3|4. | ¹Rheumatology, Allergology and Clinical Immunology, Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy; ²Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Queen Mary University of London, London, UK; ³Barts Health NHS Trust and Barts Biomedical Research Centre, National Institute for Health and Care Research, London, UK; ⁴Department of Biomedical Sciences Humanitas University and IRCCS Humanitas Research Hospital, Milano, Italy

Background. To investigate whether 1) cellular and molecular characteristics of synovial tissue (ST) differ between sexes in early, treatment-naïve rheumatoid arthritis (RA) at baseline and 6 months; 2) treatment modulates synovial histopathology and molecular signatures differently in males and females.

Methods. 202 early RA patients [142 females (70%), 60 males (30%)] enrolled in the Pathobiology of Early Arthritis Cohort (PEAC) who met the 2010 ACR/EULAR classification criteria were analyzed. Clinical and laboratory data, and ultrasound-guided synovial biopsies of active joints were collected at baseline and 6 months. Histological analysis included Krenn synovitis scoring and immunohistochemistry for macrophages, T, B and plasma cells. Based on published criteria, three synovial pathotypes were identified [1]. RNA-seq was performed on ST samples, followed by differential gene expression analysis with DESeq package and cell-type deconvolution via MCP-counter. Adjusted p<0.05 was considered significant.

Results. At baseline, a higher proportion of males showed Diffuse-Myeloid (DM) and Lympho-Myeloid (LM) pathotypes (45% and 41%) compared to females (39% and 38%), while the Fibroid (F) pathotype was more prevalent in females (23% vs 14%). Median synovitis scores were higher in males [4.5 (2.8-6)] than female [3 (2-5), p=0.073]. LM pathotype and high Krenn scores were more common in small joints in males than females (LM 38% vs 16%, p=0.0291; Krenn 5-9 50% vs 10%, p=0.005), while in large joints were more prevalent in females (LM 74% vs 14%, Krenn 5-9 70% vs 14%, p<0.001), suggesting a preferential articular involvement. Thirty-two genes were differentially expressed at baseline (1 upregulated in females, 31 in males); several male-upregulated genes (UTY, KDM5D, RPS4Y1, USP9Y, DDX3Y, EIF1AY) correlated with immune cell infiltration and tended to be more expressed in ST with high Krenn score and LM pathotype. At 6 months, females showed a smaller reduction in SJC and fewer reached a EULAR-CRP good response, despite more aggressive treatments (Figure 1A). Improvement in Krenn score was more frequent in males (74% vs 58%). After treatment, 546 genes were differentially expressed (88 upregulated in females, 458 in males). Pathways related to extracellular matrix, angiogenesis and epithelial-to-mesenchymal transition were enriched in females (Figure 1B). Fibroblast-related genes (POSTN, HAPLN1, FGFR3) were significantly upregulated in females and overexpressed in the F pathotype. MCP-counter analysis confirmed increased fibroblast abundance in females (p=0.012) (Figure 1C).

Conclusions: Molecular profiling revealed sex-specific disease mechanisms, with enhanced fibroblast and matrix remodelling signatures in females, suggesting that fibroblast activity—previously associated with poor therapeutic response [2] and treatment refractoriness [3]—may contribute to reduced treatment efficacy. Further studies are needed to directly assess the mechanism linking fibroblast signatures and therapeutic response in females.

References

1. Humby F, Lewis M, Ramamoorthi N, Hackney JA, Barnes MR, Bombardieri M, et al. Synovial cellular and molecular signatures stratify clinical response to csDMARD therapy and predict radiographic progression in early rheumatoid arthritis patients. Ann Rheum Dis. 2019;78(6):761-72.

2. Nerviani A, Di Cicco M, Mahto A, Lliso-Ribera G, Rivellese F, Thorborn G, et al. A pauci-immune synovial pathotype predicts inadequate response to TNFα-blockade in rheumatoid arthritis patients. Front Immunol. 2020;11:845.

3. Rivellese F, Humby F, Bugatti S, Fossati S, Girotto G, et al. B cell synovitis and clinical phenotypes in rheumatoid arthritis: relationship to disease stages and B cell targeted therapy. Nat Med. 2022;28(9):2041-2052.