The difference in salivary biomarkers comparing healthy children and children with juvenile idiopathic arthritis

Abstract

Aims: Children with juvenile idiopathic arthritis (JIA) have a chronic inflammatory condition often with a fluctuating disease course. Could increased levels of bacteria and inflammatory markers be a marker of disease onset and disease activity, or is it simply a consequence of the disease? Our aim with the study is to investigate inflammatory markers and two selected bacteria found in saliva in children with JIA compared to healthy children. Materials and method: Salivary samples were collected under NorJIA study, a larger Norwegian prospective multicenter cohort study on JIA. The saliva samples were used to investigate the levels of inflammatory markers and levels of S. mutans and P. gingivalis. The inflammatory markers were measured using BioPlex technology which gives us the opportunity to measure several biomolecules in the same samples simultaneously. Extracted DNA from the saliva samples were amplified and quantified by using a droplet digital PCR (ddPCR). The Mann-Whitney and the Kruskal-Wallis test was used for not normally distributed variables, and for cytokines the p-value set to > 0,01 to adjust for multiple variables. Results: In ddPCR quantification in saliva S. mutans was significantly higher in the JIA group compared to the healthy control group. For the cytokine analyses IL-2, IL-9, IL-17, basic FGF and G-CSF were significantly higher in the healthy control group compared to JIA. RANTES had significantly higher levels in the JIA group compared to the healthy control group. Conclusion: In this study, we found support for our hypothesis that children with JIA have a different concentration of inflammatory markers and a higher amount of S. mutans in their saliva compared to children without JIA. Further research is needed to reveal the association between higher amount of S. mutans and the different levels of some proinflammatory cytokines in saliva in JIA patients.