Fig. 4: AXL and MERTK synovial expression and relationship with clinical features are influenced by the disease stage and treatment exposure.

A, C AXL (A) and MERTK (C) gene expression (vst normalised reads) in synovial tissue of anti-TNF inadequate responder RA patients (R4RA cohort, n = 133) according to the histological pathotype defined as Pauci-Immune (P-I, in green), Diffuse-Myeloid (D-M, in red), and Lympho-Myeloid (L-M, in blue). Data are represented as mean ±SEM. p values were calculated using the Kruskal–Wallis test with Dunn’s post hoc test. B, D Correlation between synovial AXL (B) and MERTK (D) gene expression and semi-quantitative scores (0–4) of B cells (CD20), T cells (CD3), plasma cells (CD138), and sublining macrophages (CD68SL). p values and r-coefficients were calculated using the two-tailed Pearson correlation test. E Expression of sAxl, sMerTK (pg/mL) or the ratio between sMerTK and sAxl in the supernatant of primary fibroblasts-like synoviocytes (FLS) conditioned with supernatant from M1-polarised THP1 (SN M1) or M2-polarised THP1 (SN M2), or in the respective medium used to condition the cells (SN CT). F Expression of sAxl, sMerTK (pg/mL) or the ratio between sMerTK and sAxl in the supernatant of THP1-derived macrophages conditioned with supernatant from unstimulated RA-FLS (SN FLS) or LPS stimulated FLS (SN FLS Infl.), or in the respective medium used to condition the cells (SN CT). E, F Data are represented as mean ±SEM. p values indicated were calculated using the unpaired two-tailed t test (left and middle panels) or the two-tailed Mann–Whitney test (right panel). Experiments were performed on n = 3 distinct patient-derived FLS. G, H Heatmaps showing the correlation between AXL and MERTK synovial transcript levels at baseline and cytokines and growth factors relevant to the inflammatory response (G) and clinical parameters (H). The red/blue scale represents the Spearman r coefficient, calculated using the two-tailed Spearman correlation test. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. CRP C-reactive protein, ESR erythrocyte sedimentation rate, DAS28 disease activity score 28, TJC/28 tender joints count (0–28), SJC/28 swollen joints count (0-28), HAQ health assessment questionnaire.