Human fibroblast-like synoviocytes (FLSs) -derived secretome

Invasive pannus, mainly composed of fibroblast-like synoviocytes (FLSs), is a hallmark of rheumatoid arthritis (RA) pathology. Secreted proteins from RA-FLS play key roles in RA invasive pannus. However, RA-FLS-derived secretome associated with invasive pannus has not been systematically investigated. Here, we first identified 843 secreted proteins from RA-FLSs treated with TNFα and IL-1β using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Functional enrichment analysis revealed that 58.5% (493 proteins) of the secretome were associated with pannus-driven RA pathologies. Among them, parallel reaction monitoring (PRM) analysis then identified 16 secreted proteins that were increased in RA SFs (117 samples) than in OA SFs (45 samples). Of them, MYH9 further showed significant positive correlations with RA pathological parameters, such as synovial hyperplasia, increased articular vascularity, and inflammation severity. Molecular and cellular experiments confirmed that MYH9 was expressed in RA-FLSs and more highly under disease-aggravating conditions, and MYH9 depletion significantly defected migration and invasion of RA-FLS in RA pannus. Our study provides a comprehensive resource of RA-FLS-derived secretome, and our results suggest MYH9 that was increased in RA SF and strongly correlated with disease severity as a potential therapeutic target for invasive pannus.