Leo Tjäderhane

Matrix metalloproteinases: Contribution to pathogenesis, diagnosis and treatment of periodontal inflammation

Matrix metalloproteinases (MMPs) form a family of enzymes that mediate multiple functions both in the tissue destruction and immune responses related to periodontal inflammation. The expression and activity of MMPs in non‐inflamed periodontium is low but is drastically enhanced to pathologically elevated levels due to the dental plaque and infection‐induced periodontal inflammation. Soft and hard tissue destruction during periodontitis and peri‐implantitis are thought to reflect a cascade of events involving bacterial virulence factors/enzymes, pro‐inflammatory cytokines, reactive oxygen species and MMPs. However, recent studies suggest that MMPs can also exert anti‐inflammatory effects in defence of the host by processing anti‐inflammatory cytokines and chemokines, as well as by regulating apoptotic and immune responses. MMP‐inhibitor (MMPI)‐drugs, such as doxycycline, can be used as adjunctive medication to augment both the scaling and root planing‐treatment of periodontitis locally and to reduce inflammation systematically. Furthermore, MMPs present in oral fluids (gingival crevicular fluid (GCF), peri‐implant sulcular fluid (PISF), mouth‐rinses and saliva) can be utilized to develop new non‐invasive, chair/bed‐side, point‐of‐care diagnostics for periodontitis and dental peri‐implantitis.

The role of matrix metalloproteinases in the oral environment

This review focuses specifically on matrix metalloproteinases (MMPs) and their role in physiological and pathological extracellular matrix (ECM) remodeling and degradation processes in the oral environment. A group of enzymes capable of degrading almost all ECM proteins, MMPs contribute to both normal and pathological tissue remodeling. The expression of different MMPs may be upregulated in pathological conditions such as inflammation and tumor invasion. The balance between activated MMPs and tissue inhibitors of metalloproteinases (TIMPs) controls the extent of ECM remodeling. Prior to mineralization, MMPs may participate in the organization of enamel and dentin organic matrix, or they may regulate mineralization by controlling the proteoglycan turnover. There is evidence indicating that MMPs could be involved in the etiology of enamel fluorosis and amelogenesis imperfecta. They seem to play a part in dentinal caries progression, since they have a crucial role in dentin collagen breakdown in caries lesions. MMPs have been identified in pulpal and periapical inflammation and are strongly correlated with periodontal diseases, since they are the major players in collagen breakdown during periodontal tissue destruction. The use of MMP inhibitors could help the prevention and treatment of many MMP-related oral diseases.

Immunohistochemical identification of MMP-2 and MMP-9 in human dentin: Correlative FEI-SEM/TEM analysis.

Matrix metalloproteinases (MMPs) are a family of peptidases trapped within mineralized dentin matrix and involved with degradation of the extracellular matrix components in hybrid layers and caries. Despite their identification through indirect evidences and biochemical assays, MMP-2 and -9 have not been localized within the human dentin extracellular organic matrix. Thus, this study aimed to assess the localization and distribution of MMP-2 and -9 in human dentin organic matrix by employing a correlative field emission in-lens-scanning electron microscopy (FEI-SEM) and transmission electron microscopy (TEM) immunohistochemical approach. Dentin specimens were submitted either to a preembedding or to a postembedding immunolabeling technique using primary monoclonal antibodies anti-MMP-2 and anti-MMP-9 and exposed to a secondary antibody conjugated with gold nanoparticles. MMP-2 and -9 labelings were identified in the demineralized dentin matrix as highly electron-dense gold particles dispersed on the collagen fibrils. Correlative FEI-SEM/TEM observations confirmed that MMP-2 and MMP-9 are endogenous components of the human dentin organic matrix and revealed the three-dimensional relationship between these proteinases and the collagen fibrils, showing that both antibodies yielded a similar labeling pattern. In conclusion, the results of the study contribute to reveal distinct distribution pattern of gelatinases and support the hypothesis that these enzymes are intrinsic constituents of the dentin organic matrix after decalcification.

Matrix Metalloproteinase-13 (MMP-13, Collagenase-3) is Highly Expressed in Human Tooth Pulp

Matrix metalloproteinases (MMPs) and their specific tissue inhibitors (TIMPs) participate into extracellular matrix degradation in physiological and pathological conditions. We hypothesized that MMP expression in pulp tissue changes in response to caries attack and investigated the gene expression profiles of MMPs and TIMPs in pulp tissue of sound and carious teeth with cDNA microarray. cDNA microarray demonstrated an extremely high MMP-13 (collagenase-3) mRNA expression in pooled pulp samples of sound and carious teeth, with less pronounced expression of MMP-16 (MT3-MMP) and TIMP-1. Real-time quantitative polymerase chain reaction of individual pulp samples revealed a wide range of the MMP-13 expression level between pulp samples with possible downregulation of MMP-13 expression during caries progression. Western blot and immunohistochemical staining confirmed the presence of MMP-13 with no observable differences between sound and carious teeth pulp tissues. The results reveal that MMP-13 is expressed and synthesized in pulp tissue, an interesting feature considering the very limited expression of MMP-13 in normal adult tissues. Further studies with a larger sample size are needed to clarify the changes in MMP-13 expression during caries progression.

Healing of extraction sockets in collagenase‐2 (matrix metalloproteinase‐8)‐deficient mice

Matrix metalloproteinase-8 (MMP-8) participates in skin wound healing and inflammation. We hypothesized that MMP-8 plays a role in wound healing after tooth extraction and in periapical inflammation. Bone formation, collagen metabolism, and inflammation in tooth extraction socket and in periapical lesions were analyzed in wild-type mice and in MMP-8-deficient (MMP-8(-/-)) mice. New trabecular bone area in the extraction sockets and in periapical lesions were similar in both groups. In extraction sockets significantly more type III procollagen was synthesized, and the neutrophil and MMP-9 levels were lower in MMP-8(-/-) mice. The amount of Fas ligand, identified as a substrate for MMP-8, was lower in alveolar mucosa but higher in alveolar bone of MMP-8(-/-) mice. These results indicate that MMP-8 can modulate inflammation and collagen metabolism of alveolar bone and mucosa.

Effectiveness of low-dose doxycycline (LDD) on clinical symptoms of Sjögren's Syndrome: a randomized, double-blind, placebo controlled cross-over study

BackgroundMatrix metalloproteinases (MMPs) are proteolytic enzymes that may contribute to tissue destruction in Sjögrens syndrome (SS). Low-dose doxycycline (LDD) inhibits MMPs. We evaluated the efficacy of LDD for the subjective symptoms in primary SS patients.This was a randomized, double blind, placebo controlled cross-over study. 22 patients were randomly assigned to receive either 20 mg LDD or matching placebo twice a day for 10 weeks. The first medication period was followed by 10-week washout period, after which the patient received either LDD or placebo, depending on the first drug received, followed by the second washout period. Stimulated saliva flow rates and pH were measured before and after one and ten weeks of each medication and after washout periods. VAS scale was used to assess the effect of LDD and placebo on following six subjective symptoms: xerostomia; xerophtalmia; difficulty of swallowing; myalgia; arthralgia; and fatigue. The effect was evaluated for each medication and washout period separately.ResultsOverall, the effects of medications on subjective symptoms were minor. Wilcoxon test demonstrated increased fatigue with LDD during medication (p < 0.05). The differences may, however, reflect normal fluctuation of symptoms in SS patients.ConclusionLDD may not be useful in reducing the primary SS symptoms.