Measurement of synovium and serum dual specificity phosphatase 22 level: Their inter‐correlation and potency as biomarkers in rheumatoid arthritis

BACKGROUND: Dual specificity phosphatase 22 (DUSP22), also named as Jun N‐terminal kinase pathway associated phosphatase recently, is reported to be closely engaged in immune and inflammation regulation. This study aimed to investigate the interaction between synovium DUSP22 and serum DUSP22 levels and to explore their correlation with rheumatoid arthritis (RA) risk, inflammation, and disease activity. METHODS: Synovium and serum samples from 42 RA patients with knee involvement underwent arthroscopy, and 20 knee trauma patients were collected. Besides, serum samples from 40 healthy controls were also obtained. Synovium DUSP22 expression was detected by reverse transcription quantitative polymerase chain reaction, while serum DUSP22 level was detected by enzyme‐linked immunosorbent assay. RESULTS: Synovium DUSP22 level was greatly decreased in RA patients compared to trauma controls (p < 0.001), and it was negatively correlated with tender joint count (TJC) (r = −0.318, p = 0.040), C‐reactive protein (CRP) (r = −0.330, p = 0.033), and Lysholm score (r = −0.423, p = 0.005) in RA patients. Serum DUSP22 level was lowest in RA patients, followed by trauma controls, then highest in healthy controls (p < 0.001). Serum DUSP22 level was negatively associated with TJC (r = −0.438, p = 0.004), swollen joint count (SJC) (r = −0.372, p = 0.015), CRP (r = −0.391, p = 0.011), and disease activity score in 28 joints (DAS28(ESR)) score (r = −0.406, p = 0.008), and it increased after treatment (p = 0.001) in RA patients. In addition, serum DUSP22 level positively related to synovium DUSP22 level in RA patients (r = 0.394, p = 0.010). CONCLUSION: Synovium and serum DUSP22 are intercorrelated and insufficiently expressed in RA patients; meanwhile, their deficiency correlates with increased systemic inflammation, disease activity, and joint dysfunction.