Salivary matrix metalloproteinases during pregnancy and post-partum

Objective: Matrix metalloproteinases (MMPs) are connected to periodontal inflammation and destruction. However, their presence in saliva or role in pregnancy-related gingivitis is hardly known. The aim of this longitudinal study was to compare the salivary levels of a collagenase (MMP-8) and two gelatinases (MMP-2 and MMP-9) to periodontal status during different phases of pregnancy and post-partum. Methods: Thirty generally and periodontally healthy Caucasian pregnant women (the Pr group) and 24 non-pregnant women as their controls (the N-Pr group) were recruited in the study. In the Pr group periodontal examination was performed three times during pregnancy (at 12-14 weeks, 25-27 weeks, and 34-38 weeks of pregnancy), and twice post-partum (4-6 weeks after delivery and after lactation), and in the N-Pr group three times, once per subsequent month. At each visit, paraffin-stimulated saliva sample was collected. Salivary MMP-8 levels were assessed by immunofluorometric assay (IFMA) and the levels and activities of pro and active forms of MMP-2 and MMP-9 by gelatin zymography quantitated by densitometry. Results: Zymographic analysis revealed MMP-9 being predominant, however, the levels were significantly lower in the Pr group (p<0.0001). The levels and activities of MMP-9 maintained stable during the follow-up period in both groups. In contrast, salivary MMP-8 levels decreased significantly (p=0.05) during the second trimester in the Pr group, correlating adversely to pregnancy gingivitis seen as elevated percentages in bleeding on probing and probing pocket depth during the second and third trimester. After delivery, the MMP-8 levels returned to the same level as observed in the N-Pr group. Conclusion: Our results suggest that hormonal changes induce or enhance susceptibility to gingivitis, which is reflected significantly in reduction of salivary collagenase levels, while salivary gelatinase levels are not affected.