Salivary MMP-8 and Periodontal Inflammatory Burden in Rheumatoid Arthritis

Objectives: We compared periodontal inflammatory burden by analyzing salivary matrix metalloproteinase (MMP)-8 concentrations in patients with early and chronic rheumatoid arthritis (RA) with respect to RA disease activity and the used antirheumatic medication. We expected differences between the groups.
Methods: In this prospective follow-up study 81 RA patients, 53 early untreated RA (ERA) and 28 chronic RA (CRA) patients with insufficient response to synthetic disease modifying antirheumatic drugs (DMARDs), underwent rheumatological and dental examinations including MMP-8 analyses by immunofluorometric assay from salivary samples. Periodontal inflammatory burden (PIBI) and total dental index (TDI) were calculated. After examination, ERA patients started treatment with synthetic DMARDs, systemic low-dose glucocorticoids, and intra-articular glucocorticoid injections. CRA patients were candidates for biological DMARDs. The patients were re-examined 16 months later. Controls were 43 age, gender-, and place of domicile-matched volunteers. Results were statistically analyzed using Student’s t-test or Kruskal-Wallis test between groups, and nonparametric Wilcoxon test when comparing related samples between baseline and follow-up.

Results: Compared to controls, PIBI and TDI were higher in RA groups (p<0.001 and p=0.012, respectively).
MMP-8 concentration was significantly higher in ERA group vs. CRA and controls with lower PIBI (p=0.003) and TDI (p=0.046) at baseline, while within CRA group MMP-8 increased parallel to PIBI values both at baseline (p=0.008) and at follow-up (p=0.002). The used antirheumatic medication including glucocorticoids had no impact on MMP-8 concentration among the RA groups. The activity of RA did not either correlate with MMP-8.

Conclusions: Elevated salivary MMP-8 concentrations associated with periodontal indices among RA patients and even at early stage of RA disease MMP-8 concentrations were high. Thus, salivary MMP-8 analyses could be used in assessing oral inflammatory burden in rheumatoid arthritis. However, more studies are needed to investigate more widely the effect of RA duration, disease activity, and used antirheumatic medication.
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