During a five-year period at Helsinki University Hospital, a tertiary care hospital, 41 patients aged 17 or under, were identified as having parotitis; from 36 of these patients, saliva samples were collected for MMP-8 IFMA (time-resolved immunofluorometric assay) analyses. Control saliva samples were collected from 34 age- and gender-matched children admitted for an elective surgery who had no history of parotitis. For comparison, salivary levels of MMP-9, tissue inhibitor of matrix metalloproteinase (TIMP-1), MMP-8/TIMP-1 ratio, human neutrophil elastase (HNE), and myeloperoxidase (MPO) were analyzed by ELISA. Additionally, salivary MMP-8 levels were compared to historical saliva samples from 18 adult gingivitis patients as well as to 10 healthy adult controls.
The median (25%, 75% percentile) MMP-8 concentration in saliva of parotitis patients was significantly lower than MMP-8 concentration in saliva of their controls [50.4 ng/ml (37.5, 72.9) vs. 148.5 ng/ml (101.2, 178.5) p < 0.0001] and lower than in patients with gingivitis [347.9 ng/ml (242.6, 383.2) p < 0.0001] or healthy adult controls [257.2 ng/ml (164.9, 320.7) p < 0.0001]. The MMP-8/TIMP-1 ratio was lower than in controls [0.13 (0.05–0.02) vs. 0.3 (0.17–0.46) p < 0.0001]. The median MMP-9 concentration in saliva of parotitis patients was significantly higher than in controls [143.9 ng/m (68.8–189.0) vs. 34.9 ng/ml (16.3–87.6) p < 0.0001]. Neither HNE, MPO, nor TIMP-1 alone separated the patients from the control groups.
MMP-9 was up-regulated in juvenile parotitis saliva, suggesting that MMP-9 may play a destructive role in juvenile parotitis, as others have suggested. The present novel findings reveal a decreased salivary MMP-8 concentration, suggesting that MMP-8 may reflect in juvenile parotitis down-regulated or anti-inflammatory immune characteristics.