Transamidase and collagenase activity in healthy and diseased human gingival tissues

Matrix Metalloproteinase-2 May Be Involved With Increased Bone Loss Associated With Experimental Periodontitis and Smoking: A Study in Rats

BACKGROUND

Smoking has been associated with periodontitis severity and is considered a risk factor for its development. It has been reported that matrix metalloproteinase (MMP) produced by host cells plays a major role in periodontal tissue destruction. Thus, the present study tested, in rats, the hypothesis that local increased levels of MMP-2 would be associated with the enhanced periodontitis-related bone loss after intermittent cigarette smoke inhalation (CSI).

METHODS

Twenty-seven adult male Wistar rats were used. A ligature was placed around one of the mandibular first molars of each animal and they were randomly assigned to the following control (N = 13) or CSI (N = 14) group. Sixty days later, the animals were sacrificed, the gingival tissues harvested, and the specimens processed for decalcified sections. Extracts from the gingival tissues were prepared and assayed for MMP-2 expression.

RESULTS

Intergroup comparisons (unligated sites) showed that CSI might directly affect alveolar bone (0.16 +/- 0.03 mm2 versus 0.24 +/- 0.09 mm2 for non-smokers and smokers, respectively; P = 0.001). Moreover, CSI significantly enhanced bone loss resulting from experimental periodontitis (0.64 +/- 0.36 mm2 versus 1.50 +/- 0.50 mm2 for non-smokers and smokers, respectively; P<0.05). In addition, zymography demonstrated that CSI also enhanced both MMP-2 levels and activity in the gingival tissues around ligated teeth.

CONCLUSION

Within the limits of the present investigation, it can be assumed that the effect of CSI on MMP-2 levels and activity may account for the increased periodontitis progression rate observed in smokers.

Expression and activity of matrix metalloproteinase-2 (MMP-2) in the development of rat first molar tooth germ

Tooth germ development is associated with morphological and biochemical changes of the dental papilla and enamel organ. Enzymes with gelatinolytic activities were studied by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and enzymography in tooth germ of newborn to 15-day-old rats. Three major bands with gelatinolytic activity were detected at all periods and characterized as the latent and active forms of MMP-2 using their molecular weight and activity dependent on Zn++ and Ca++ ions as criteria. Expression and activity of MMP-2 increased progressively from 0 to 15 days after birth. Mechanical separation of the tooth germ from 10-day-old rats showed that the gelatinolytic activity was localized mainly in the dental papilla and not the dental organ. These data indicate that the expression and activity of MMP-2 varies during the development and maturation of rat first molar tooth germ.

Cytokines modulate routes of collagen breakdown. Review with special emphasis on mechanisms of collagen degradation in the periodontium and the burst hypothesis of periodontal disease progression

In this paper, we review recent work on collagen degradation, 2 main routes of breakdown are described and their relevance during healthy and inflammatory conditions of the periodontium is discussed. Special attention is paid to the possible role of cytokines, in particular interleukin 1 (IL-1) and transforming growth factor beta (TGF-beta), on the modulation of collagen phagocytosis and metalloproteinase production. IL-1 has been shown to have a dual function in collagen digestion. It inhibits the intracellular phagocytic pathway, but at the same time, it strongly promotes extracellular digestion by inducing the release of collagenolytic enzymes like collagenase. TGF-beta has an opposite effect on both pathways and antagonizes IL-1. Collagenase is released in an inactive form, and a considerable fraction of the proenzyme may become incorporated in the extracellular matrix. This reservoir of latent enzyme can be activated (for instance by plasmin), leading to a sudden and extensive breakdown of the collagenous fibre meshwork. It is suggested that this phenomenon may also take place during progressive periodontitis and could explain an episodic nature of collagenolysis, clinically resulting in bursts of attachment loss (burst hypothesis).

Matrix metalloproteinases-1 and -8 and TIMP-1 mRNA levels in normal and diseased human gingivae

Interstitial collagenases, including matrix metalloproteinase-1 (MMP-1) and -8 (MMP-8), serve as initiators of extracellular matrix destruction in periodontal disease. Collagenase activities are mainly regulated by tissue inhibitors of metalloproteinases (TIMPs). We tested the effects of inflammation on MMP-1 and MMP-8 gene expression in periodontal disease. To determine the relative abundance of these mRNAs in gingiva, we used a reverse transcription-polymerase chain reaction (RT-PCR) assay. Gingival biopsies were divided into 2 groups; a control group and an inflamed group with severe gingivitis or periodontitis. The MMP-1 mRNA levels were significantly elevated in inflamed gingiva, while the levels of the MMP-8 transcript were not different in the 2 groups and barely detectable by RT-PCR assay. The expression of the TIMP-1 gene was not altered, and remained higher than any of these other genes in both control and diseased gingivae. These results suggest that MMP-1 rather than MMP-8 may play an important role in the initiation of collagen degradation in periodontal disease. However, the possibility remains that MMP-8 plays an important role in periodontal tissue destruction, since the mRNA abundance and not the enzyme activity was assessed.