Fig. 2: RA synovial microenvironment-induced activation of mast cells.

Synovial mast cells were enriched from digested synovial tissues of OA and RA patients by magnetic bead sorting for CD117⁺ cells and used for label-free mass spectrometry. a Mast cell purity was confirmed by tryptase staining of enriched CD117⁺ cells. Red, tryptase; Blue, DAPI. Scale bar: 25 μm. Data are representative of three independent experiments. b Heatmap of top 50 differentially expressed proteins between synovial mast cells from OA and RA patients by hierarchical clustering after z-score normalization. Upregulated and downregulated proteins in RA synovial mast cells were depicted in red and blue, respectively. c, d GO analysis and KEGG pathway analysis of differentially expressed proteins showed enriched terms including mitochondria metabolism, energy metabolism, and leukocyte migration, along with strong changes in metabolic pathways. e Overexpression of oxidative phosphorylation related proteins in synovial mast cells from RA patients by GSEA. f Representative images of toluidine blue-stained synovium from OA and RA patients. Resting mast cells and degranulated mast cells were indicated by purple and red markers, respectively. Scale bar: 25 μm. g Statistical analysis of mast cell degranulation rate by counting five fields of view (n = 10 biologically independent samples for each group, P < 0.0001). Data are presented as the mean ± SEM and analyzed using two-tailed unpaired t test (c, d, g), ****P < 0.0001. The P-values are adjusted in multiple comparisons (FDR < 1% for c and d). Source data are provided as a Source Data file.