Pos0739 leucocyte abnormalities and cytokine levels in synovial fluid of juvenile idiopathic arthritis patients: a preliminary study

Background Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases characterized by joint inflammation and uveitis is the most frequent extra-articular manifestation [1,2]. Although several studies evaluated the differences between the different types of JIA, no specific markers have been identified which would allow early stratification of patients and predict the future disease course. Recently, it has been suggested that rheumatic diseases might be associated with genomic instability and increased sensitivity to DNA damage (3), but it has not yet determined in JIA. Objectives To investigate cell populations, cytokine levels, and signs of genotoxicity in synovial fluid (SF) of patients with different JIA subtypes. Methods SF was collected from the knees of 24 patients, untreated for at least 6 months prior to enrollment, and fulfilling ILAR criteria (4): 9 with polyarticular (poly)-JIA (age:6.56±4.67 years) and 15 with oligoarticular (oligo)-JIA (age:8.33±5.15 years). Six poly-JIA and 8 oligo-JIA patients were at disease onset. Among the oligo-JIA patients, 12 had positive antinuclear antibodies (ANA+) and 5 had uveitis. SF was examined under optical light microscopy. White cell count (WBC) and the polymorphonuclear cell (PMN) percentage were determined in SF according to standard procedures. May-Grünwald-Giemsa staining was used to determine the percentage of hypo- or hypersegmented PMN, binucleated monocytes, and cells with micronuclei (MN), pyknosis, necrosis, apoptosis and nuclear buds, which are considered biomarkers of genotoxic events. SF IL-1β and IL-8 levels were assayed by ELISA. Results WBC count and PMN percentage were higher in SF of patients with poly-JIA than in those with oligo-JIA, albeit not significantly. Comparison between the two groups at disease onset showed that WBC levels and PMN percentage were significantly greater in SF from poly-JIA (poly-JIA WBC:10500±4580.32 cells/mm 3 , PMN:59.83±13.75%; oligo-JIA WBC:4850±1050 cells/mm 3 , PMN:41.5±16%; p<0.05). IL-1β and IL-8 levels were higher in children with poly-JIA, but the difference reached statistical significance only for IL-8 in patients at disease onset (poli-JIA:1253.19±264.4 pg/ml; oligo-JIA:519.67±468.34 pg/ml; p<0.01). This group also showed a percentage of cells with MN significantly greater as compared to that in oligo-JIA (poli-JIA:7.1±2.42%; oligo-JIA:1.75±2.05%; p<0.001). Although SFs from oligo-JIA-ANA+ patients had higher WBC and PMN percentage than those from oligo-JIA-ANA-, no significant differences were observe between the 2 groups. SFs from oligo-JIA patients with uveitis showed higher but not significant IL-8 levels (554.06±520.26 pg/ml), significantly greater IL-1β concentrations (100.94±76.05 pg/ml; p<0.05) and percentage of cells with MN (5.73±3.06%; p<0.05), and significantly lower hypersegmented PMN percentage (11.06±8.45%; p<0.05) than those from oligo-JIA patients without uveitis (IL-8:280.88±310.11 pg/ml; IL-1β:6.04±15.4 pg/ml; cells with MN:1.96±2.36%; hypersegmented PMN:22.79±8.07%). There was no significant difference in the other studied parameters between the different patient groups. Conclusion This study shows that poly-JIA SFs have higher inflammation marker levels than oligo-JIA SFs, and this is observed mostly at the disease onset. The presence of MN may be associated with SF genotoxic effects, and trigger the induction of inflammatory pathways that contribute to disease complications. As hypersegmented PMN suppress T cell proliferation, a low cell number with this phenotype may reflect a persisting antigenic stimulus. References [1]Ravelli A, et al. Lancet 2007;369:767– 78 [2]Zulian F, et al. J Rheumatol 2002;29:2446-53 [3]Souliotis VL, et al. Int J Mol Sci 2019;21:55 [4]Petty RE, et al. J Rheumatol 2004;31:390-2 Acknowledgements: NIL. Disclosure of Interests None Declared.