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REVIEW |
1 Groupe Matrice Extracellulaire et Biominéralisation (EA 2496) and
2 Department of Conservative Dentistry and Endodontics, Faculté de Chirurgie Dentaire, 1 rue Maurice Arnoux, 92120 Montrouge, Université Paris 5, France; and
3 Laboratoire CRRET, CNRS UMR 7149, Université Paris XII, Créteil, France
* corresponding author, catherine.miller{at}univ-paris5.fr
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ABSTRACT |
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 TOP ABSTRACT (I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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KEY WORDS: caries • matrix metalloproteinases • saliva • dentin • MMP inhibitors
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(I) INTRODUCTION |
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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The dynamic process of demineralization that occurs numerous times daily is usually balanced by the properties of the saliva (buffer, flow rate, inorganic content, etc.) that allow remineralization to occur. However, caries progresses when this balance is lost and pathological factors predominate (Featherstone, 2004). A caries lesion can be initiated either in the enamel or in the cementum and eventually progresses to the underlying dentin. Dentin is a calcified tissue, which possesses an important organic matrix (30% vol) containing collagen (90%) and non-collagenous proteins (10%). During the caries process, the mineral part of dentin is dissolved, exposing the organic matrix to breakdown by bacterially derived enzymes, as well as by host-derived enzymes such as the MMPs present within the dentin. MMPs derived from saliva may also be involved, since saliva has direct access to the caries-affected dentin.
Matrix metalloproteinases (MMPs), also designated as matrixins, hydrolyze components of the extracellular matrix (Brinckerhoff and Matrisian, 2002). Currently, 24 MMP genes have been identified in humans, and 26 well-characterized members have been reported (Table
). Most are multidomain proteins that can be broadly defined by several parameters, including their ability to cleave matrix components, their dependence on a zinc ion for activity, the requirement that the enzymes be activated by the cleavage of a prodomain, the conservation of specific amino acid sequences between family members, and inhibition of their enzymatic activity by endogenous tissue inhibitors of metalloproteinases (TIMPs) (Birkedal-Hansen et al., 1993; Nagase and Woessner, 1999). These proteinases play a central role in many biological processes, such as development, normal tissue remodeling, and angiogenesis. They also play a key role in wound healing and in diseases such as atheroma, arthritis, cancer, and tissue ulceration (Visse and Nagase, 2003).
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(II) REGULATION, STRUCTURE, AND FUNCTION OF MMPs |
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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MMP expression and activity are precisely regulated at the level of transcription, secretion, activation of the precursor zymogens, interaction with specific ECM components, and inhibition by endogenous Tissue Inhibitors of Metalloproteinases (TIMPs). Transcription can be induced by various signals, including cytokines, growth factors, mechanical stress, and changes in the extracellular matrix leading to modification in cell-matrix interactions (Overall and Lopez-Otín, 2002). Because MMPs are secreted as inactive zymogens, they must be activated, usually by proteolytic cleavage of their NH2-terminal prodomains. Some MMPs are activated by serine proteases (such as plasmin, tissue kallikrein, and furin), by bacterial proteinases, or by other members of the MMP family. The best-characterized is the activation of pro-MMP-2 by MT1-MMP, which requires the binding of TIMP-2 to both MT1-MMP and to the proMMP-2, thus localizing the zymogen close to a neighboring active MT1-MMP. Pro-MMPs can also be activated by non-proteolytic agents, such as SH-reactive agents, mercurial compounds, acids, reactive oxygen, and denaturants (Nagase and Woessner, 1999). Additional regulation of MMP activity is accomplished by the presence of endogenous MMP inhibitors, such as 
2-macroglobulin and the TIMPs. There are four human TIMPs, all of which are low-molecular-weight secreted proteins that bind non-covalently to the active site of MMPs in a 1:1 ratio. MMP activity is thus tightly regulated in normal physiological processes, but when one or more of these regulatory controls are by-passed, excessive degradation and tissue destruction may occur.
MMPs are classified into six groups based on their structural homology and their substrate specificity (Table
): collagenases (MMP-1, MMP-8, MMP-13, and MMP-18), gelatinases (MMP-2 and MMP-9), stromelysins (MMP-3, MMP-10, and MMP-11), transmembrane MMPs (MT-MMPs) (MMP-14, MMP-15, MMP-16, MMP-17, MMP-24, and MMP-25), matrilysins (MMP-7 and MMP-26), and "other" (MMP-12, MMP-19, MMP-20, MMP-21, MMP-22, MMP-23, MMP-27, and MMP-28) (Visse and Nagase, 2003). All MMPs share a common domain structure, although not all domains are represented in all family members (Fig. 1). All have a signal peptide sequence, an amino-terminal catalytic domain, containing the highly conserved Zn binding site, and a hemopexin-like carboxy-terminal domain. The latency of the enzyme is maintained by an unpaired cysteine sulfhydryl group in the propeptide domain, which interacts with the active site zinc ion. Activation requires that this cysteine-zinc interaction be perturbed by normal proteolytic removal of the propeptide domain, or by ectopically induced conformational change. This liberates the active site zinc to bind a water molecule that can then attack the peptide bonds of the protein substrate. The catalytic domain is connected to the hemopexin domain by a hinge region and is important in determining the substrate specificity of the MMP as well as interactions with TIMPs, although it is lacking in the two matrilysins. The two gelatinases, MMP-2 and MMP-9, have a gelatin-binding domain in the catalytic domain, which contains 3 fibronectin-type II repeats. The 6 membrane-type MMPs are inserted into the plasma membrane by a carboxy-terminal transmembrane domain or a glycosylphosphatidylinositol (GPI) anchor. Several MMPs can be activated by furin-like proprotein convertases, since they contain an insert in their propeptide, which is cleaved by these convertases (Bode et al., 1999; Overall and Lopez-Otín, 2002).
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Since MMPs have so far been implicated in physiopathological events in almost all tissues of the organism, this review evaluates, more specifically, their possible role in dentin destruction during caries.
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(III) THE DENTIN EXTRACELLULAR MATRIX, POTENTIAL SUBSTRATE TO PROTEINASES DURING DECAY CAUSED BY CARIES |
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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Type I collagen constitutes about 90% of the dentin organic matrix. In odontoblasts, in culture, or in certain pathological situations, such as dentinogenesis imperfecta, types III and V collagen have also been identified, but at a lower level (1–3%) (Munksgaard et al., 1978; Waltimo et al., 1994; Butler and Ritchie, 1995). In general, collagens can be degraded by the human interstitial collagenases, which include MMP-1, MMP-8, and MMP-13, resulting in the release of 3/4- to 1/4-length peptides. These peptides lose the triple-helical conformation and can then be further degraded by the gelatinases MMP-2 and MMP-9. However, the specific cross-links (pyridinolines) between the collagen sub-units observed in dentin may provide collagen fibrils with extreme resistance to degradation (Knott and Bailey, 2000).
Phosphorylated proteins form the bulk of the remaining 10% of dentin organic matrix. They include the transient dentin phosphosialoprotein (DSPP), which is cleaved immediately after secretion into a dentin sialoprotein (DSP) and dentin phosphoprotein (DPP). These two molecules, the most abundant of the phosphorylated proteins in dentin, were first thought to be dentin-specific, but have since been detected in bone (Qin et al., 2002), although at a much lower level than in the dentin (Baba et al., 2004). They are grouped under the name of Small Integrin-Binding Ligand N-linked Glycoproteins (SIBLINGs) (Fisher and Fedarko, 2003). Other major phosphorylated proteins of the SIBLINGs family are the dentin matrix protein-1 (DMP-1), osteopontin (OPN), and bone sialoprotein (BSP). It is interesting that OPN and BSP have been detected in multiple malignant tissues, and high levels were also reported in the blood of breast, lung, colon, and prostate cancer patients (Bellahcene et al., 1994, 1996; Waltregny et al., 1998; Fedarko et al., 2001). All SIBLINGs are expressed by genes localized in humans to the chromosome 4 locus 20–21, precisely where the genetic defect dentinogenesis imperfecta has been localized (MacDougall et al., 1996; MacDougall, 1998). More recently, the gene for another SIBLING, the matrix extracellular phosphorylated glycoprotein (MEPE), was also detected close to this locus on the same chromosome (Fisher and Fedarko, 2003).
The SIBLING molecules can form specific complexes with different MMPs, in either their latent or active forms (Fedarko et al., 2004). Thus, BSP is able to bind specifically to MMP-2, OPN to MMP-3, and DMP-1 to MMP-9. After binding the corresponding MMP, a SIBLING is then able not only to activate the latent form by promoting structural changes, but also to restore MMP activity previously inhibited by binding to a specific TIMP (Fedarko et al., 2004). Therefore, MMPs may be enzymatically active in areas with high SIBLING concentrations, and may promote tissue remodeling even in the presence of TIMPs.
Dentin also contains weakly phosphorylated matrix molecules, such as amelogenin (Fincham et al., 1999) and some proteoglycans (Anderson and Schwartz, 1984), as well as non-phosphorylated proteins, which mainly include osteonectin (SPARC protein or BM40) and osteocalcin. While osteonectin may contribute to the mineralization process, osteocalcin and a close parent, the matrix Gla protein, have been suggested to serve as nucleator inhibitors (Ducy et al., 1996).
The small leucine-rich proteoglycans (SLRPs)—such as decorin, biglycan, fibromodulin, lumican, and osteoadherin—have been identified in dentin. Although they are not specific to dentin and can be found in many other mineralized or non-mineralized tissues, they have been implicated in dentin formation and mineralization (Embery et al., 2001). They are thought to be involved in the transport of collagen fibrils through the predentin and in collagen fibrillation (Goldberg et al., 2003b). They are extremely susceptible to degradation, both by MMPs, such as MMP-3 (Hall et al., 1999), and by bacterial enzymes (Rostand and Esko, 1997; Smith et al., 1997; Schmidtchen et al., 2001).
Dentin was also shown to contain several growth factors, such as transforming growth factor beta 1 (TGF-ß1), basic fibroblast growth factor (FGF-2), and insulin-like growth factors I and II (ILGF I and II) (Finkelman et al., 1990). It may be hypothesized that these growth factors can be released upon matrix degradation during the caries process and made available to stimulate the formation of reactionary dentin by the odontoblasts (Farges et al., 2003). The growth factors can also favor the recruitment of new odonto/osteoblast-like cells and stimulate their proliferation. It is of interest that several of these growth factors (TGF ß1, ILGF) have been shown to be activated by MMPs (Mu et al., 2002; Sadowski et al., 2003).
Other components identified in dentin include phospholipids (Goldberg and Boskey, 1996) and serum-derived proteins, such as albumin (Kinoshita, 1979) and 2HS glycoprotein. The latter was shown to be preferentially accumulated in mineralized tissues (Takagi et al., 1990). These various dentin components represent potential substrates for degradation by proteinases such as MMPs. Indeed, the localization of several MMPs in dentin (see paragraph VI) would be consistent with the notion that these enzymes can participate in the degradative process associated with caries development.
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(IV) THE DENTIN CARIES LESION |
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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To begin with, the initial stages of dentin caries require the bacterial invasion of the dentino-enamel junction (DEJ), then the enlargement of the gap between enamel and dentin, the spreading of the lesion along the DEJ, and the enlargement of the initial lesion, with the superficial destruction of the mantle dentin. When the enamel fragments that are no longer sustained by dentin collapse, a cavity forms which fills with food debris and is bathed in saliva (Ekstrand et al., 2001). The zone of bacterial invasion covers a more or less infected leather-like demineralized zone (Fig. 2). At this localization, the degradation of the peritubular dentin indicates the speed of formation of the caries lesion (Fig. 3). If the lesion expands rapidly, this peritubular zone is degraded and therefore missing or very thin. If the lesion progresses slowly, a sclerotic zone forms at the bottom of the lesion, with calcium phosphate re-precipitations in non-apatitic forms.
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(V) HOST-DERIVED MMPs FROM SALIVA |
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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2-macroglobulin, a non-specific inhibitor of MMP, which—in normal situations, where the concentration of MMPs is not elevated—would keep the MMPs in an inactive form (Birkedal-Hansen, 1993). Collagenases have not been detected in the salivary glands (Sorsa et al., 1990; Uitto et al., 1990). This is consistent with the fact that the saliva of edentulous subjects contains markedly less collagenase than the saliva of subjects with a full dentition and healthy periodontium (Sorsa et al., 1990; Uitto et al., 1990), and that a significant correlation exists between total collagenase activity in the whole saliva and that in the GCF (Iijima et al., 1983). Different cells, such as gingival fibroblasts, macrophages, and epithelial cells, contribute to GCF collagenase production. However, several reports strongly suggest that the PMN leukocytes that migrate through the sulcular epithelium into the gingival sulcus are the main source of salivary collagenases (Sorsa et al., 1990; Uitto et al., 1990). Both MMP-1 (interstitial collagenase) and MMP-8 (PMN-derived collagenase) can be found in saliva, whatever the subject’s periodontal status. In healthy gingiva, salivary collagenases exist mainly in the latent form, while they appear to be activated in periodontitis (Sorsa et al., 1990; Uitto et al., 1990). Higher levels of MMP-8 are also detected in the saliva of subjects affected by periodontitis compared with healthy patients, whereas the levels of salivary MMP-1 are similar in both groups (Ingman et al., 1996). There are no reports on collagenase-3 (MMP-13) in either saliva or GCF.
Saliva has also been shown to contain gelatinases (Ingman et al., 1994; Makela et al., 1994; van Strijp et al., 2003), which appear to originate mainly from the GCF (Teng et al., 1992; Ingman et al., 1994). Saliva specimens from edentulous adults have low but detectable gelatinase activity. Indeed, in pure parotid (Wu et al., 1997) and sublingual gland secretions, only traces of gelatinolytic activity could be detected. MMP-9 was shown by zymography and Western blot to be the main gelatinase in the whole saliva and in the GCF, while MMP-2 was present primarily in the form of a higher-molecular-weight complex (200 kDa) (Makela et al., 1994; van Strijp et al., 2003). Higher levels of MMP-9 and MMP-2 have been detected in the saliva of patients affected by periodontitis (Teng et al., 1992; Makela et al., 1994). Stromelysin-1 (MMP-3) was also shown to be present in the GCF, but has not been detected in saliva (Ingman et al., 1996). However, this MMP has recently been identified within the ductal elements of human salivary glands (Ogbureke and Fisher, 2004), associated with the SIBLING OPN.
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(VI) HOST-DERIVED MMPs FROM DENTIN |
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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Studies on the mouse model of tooth development have shown that, at the onset of dentinogenesis, MMP-2 expression is low but gradually increases during dentin formation, reaching maximum value at day 6–7 post-natal. In contrast, MMP-9, present at the early stages of tooth bud formation, declines gradually and becomes a minor component when dentinogenesis starts (Bourd-Boitton et al., 2005). These MMPs, MMP-2 and MMP-9 as well as MMP-3, are thought to target the components of the basement membrane (BM), degrading type IV collagen and the non-collagenous proteins such as laminins and proteoglycans. The degradation of the BM allows for direct epithelio-mesenchymal contact between cell processes and the unmineralized dentin matrix, a prerequisite for odontoblast and ameloblast terminal cytodifferentiation (Sahlberg et al., 1992, 1999; Heikinheimo and Salo, 1995). At the later stages of development, MMP-2 and MMP-9 were shown to be concentrated near the DEJ, along the mantle dentin, where TIMP-1 and TIMP-2 were at their lowest levels (Goldberg et al., 2003a). This high ratio of MMP-2 and MMP-9 to TIMPs at the DEJ suggests a high proteolytic potential, which may contribute to the extension of the caries lesion at this location.
Work from our laboratory has previously shown that MMP-3, which has a proteoglycanase activity, forms an immunoreactive band at the junction between the inner third and the outer two-thirds of predentin (Hall et al., 1999). This is precisely the area where a shift in the glycosaminoglycan (GAG) type occurs, with a marked decrease in CS/DS GAGs and an increase of KS GAGs. While GAGs and PGs can be easily extracted by acidic solution, chelators, or specific enzymes such as chondroitinases, it is possible that MMP-3 also participates in the degradation of these matrix components during the caries process.
Enamelysin (MMP-20), whose major substrate is thought to be amelogenin, is expressed by both ameloblasts and odontoblasts (Bourd-Boittin et al., 2004). Odontoblasts also express spliced forms of amelogenins, initially termed Chondrogenic Inducing Agents (CIA) and later A+4 and A-4 (Veis et al., 2000), which were suggested to play some role in odontoblast differentiation. The highest concentration of MMP-20 is found mainly in the forming enamel, and this proteinase possibly contributes to specific amelogenin degradation, mostly in the outer enamel layers (Bourd-Boittin et al., 2004). Therefore, all these enzymes detected in the dentin have the potential to degrade the matrix during pathological situations, but their precise role and their involvement in the caries process remain to be elucidated.
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(VII) ACTIVATION OF MMPs IN ACIDIC ENVIRONMENT AND POTENTIAL ROLES IN DENTIN DEGRADATION |
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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Low pH and heat treatment may also directly lead to MMP activation (Davis, 1991; Gunja-Smith and Woessner, 1993). The change in pH can alter the conformation of the propeptide and induce the cysteine switch, which represents a critical step in the activation process. During caries activity, the release of acids by bacteria rapidly decreases the pH, and the acidic environment can then activate host-derived pro-MMPs from both dentin and saliva.
The capacity of a range of acidic pH (from 4.5 to 6) to activate in vitro human salivary MMPs was assessed on the gelatinolytic activity of several saliva samples and compared with that of the organomercurial compound p-aminophenylmercuric acetate (APMA), the most commonly used activator of MMPs in vitro (Sulkala et al., 2001). The results demonstrated the greatest activity at the lowest pH examined (pH = 4.5). Furthermore, when an MMP inhibitor, the non-antimicrobial chemically modified tetracycline-3 (CMT-3) was included, the best inhibition was obtained at the lowest pH, and was more effective than the association of the same inhibitor with APMA. Analysis of these in vitro data confirms the capacity of acidic pH to activate MMPs and suggests that host-derived MMPs can be activated by acidic pH resulting from lactate release by cariogenic bacteria.
It is generally regarded that MMPs, although activated, cannot degrade the organic matrix of dentin at acidic pH. However, in the caries process, the pH drop is followed by pH neutralization due to the salivary buffer systems. Therefore, a momentary increase in pH, occurring at the spots of demineralized dentin, allows the pH-activated MMPs to degrade the organic matrix (Tjäderhane et al., 1998). Furthermore, the phosphorylated proteins released during dentin matrix demineralization by bacterial acids could interact with TIMP-inhibited host MMPs within the lesion and reactivate them, hence enhancing the degrading activity.
Several MMPs, such as MMP-2, MMP-9, and MMP-8, were identified in soft dentin lesions by Western blot analysis and gelatin zymography. The gelatinases were detected in both their latent and active forms (Tjäderhane et al., 1998). MMP-20 was observed by immunohistochemistry in dilated dentinal tubuli of caries lesions, although no reactivity could be detected by Western blotting of soft carious dentin (Sulkala et al., 2002). The authors concluded that MMP-20, produced during primary dentinogenesis by the dentin-pulp complex, is incorporated into dentin and may be released and possibly activated during caries progression.
The incubation of demineralized dentin slabs with acid-pre-treated saliva resulted in the degradation of the organic layer, as observed by transmission electron microscopy and by scanning electron microscopy (Tjäderhane et al., 1998). This clearly demonstrates that acid-activated salivary MMPs can degrade dentin matrix. MMP-9, which represents the major MMP in the dentin caries lesion and in whole saliva, appears to be particularly important in this respect, since the active form of this enzyme was consistently detected by gelatin zymography performed on several caries lesions (Tjäderhane et al., 1998). Although a recent study has found no direct correlation in situ between the activity of these enzymes and the degradation of dentin collagen (van Strijp et al., 2003), an in vivo study in the rat demonstrated that MMP inhibition by several synthetic inhibitors reduced dentin caries progression under fissures (Sulkala et al., 2001). This suggests the necessity for further investigation into the role of host MMPs in the progression of caries disease, but also highlights the interest in using MMP inhibitors in the prevention of dentin destruction. Therefore, the next part of this review will focus on the different MMP inhibitors identified to date.
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(VIII) MMP INHIBITORS AND DENTIN CARIES: TOWARD THERAPEUTIC OPPORTUNITIES |
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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TIMPs maintain a balance between matrix destruction and formation. The balance between MMPs and TIMPs is disrupted in many diseases and can result in either excess tissue degradation, as in rheumatoid arthritis and in malignancy, or in accumulation of extracellular matrix, as in fibrotic diseases (Wojtowicz-Praga et al., 1997; Overall and Lopez-Otín, 2002). The current trend of seeking to re-address the MMP-TIMP balance to block or reverse disease progression involves either increasing the local concentration of TIMPs (Baker et al., 2002) or inhibiting MMP activity by small synthetic inhibitors, as will be described below. These studies have used recombinant TIMPs or basic gene transfer systems (plasmids or retroviruses), both in cancer and in cardiovascular disease, and were shown to block disease progression (Ahonen et al., 2002; Baker et al., 1999; George, 2000).
It has been shown that salivary-derived TIMP-1 retained stability at low pH (Drouin et al., 1988), and therefore could remain active after pH increase and exert a potential inhibitory role on host-derived MMPs in dentin caries progression (Tjäderhane et al., 1998). However, in active caries lesions, the level of TIMPs may be insufficient to block destruction progression. Increasing the local concentration of TIMPs in the caries lesion may limit matrix destruction and promote remineralization and, thus, represents a potential strategy for future therapy.
(B) Synthetic MMP Inhibitors
Most of the first-generation MMP inhibitors were designed as collagen-mimicking peptides containing the collagen aminoacid sequence near the collagenase cleavage site, combined with a zinc-binding hydroxamate moiety to inhibit enzymatic activity. Other zinc-chelating groups, such as succinates, have since been developed. Batimastat and marimastat are collagen-mimicking hydroxamates, developed by British Biotech Pharmaceuticals, and have been the most-studied in terms of pre-clinical and clinical development (Rasmussen and McCann, 1997). Batimastat was one of the first-generation inhibitors to be studied in humans with advanced malignancies, but its usefulness has been limited by its poor water solubility, requiring intraperitoneal administration of the drug as a detergent emulsion. This led to the development of second-generation MMP inhibitors, such as marimastat, which are orally available and were the subject of Phases I/II/III clinical trials in North America and Europe (Wojtowicz-Praga et al., 1997). Their performance and efficacy have been very limited in the setting of advanced metastatic cancer (Evans et al., 2001; Bramhall et al., 2002; Overall and Lopez-Otín, 2002) and were accompanied by unwanted side-effects, notably arthralgia and myalgia (Evans et al., 2001). Several other new agents have since been developed—for example, CT 1166 has been shown to inhibit MMPs effectively (Fanchon et al., 2004).
The use of these drugs, which were mainly developed for cancer therapy, seems to be inappropriate for dentin caries inhibition, since they are associated with important side-effects. However, for controlling tooth decay, topical application of these agents may be sufficient, although the development of new selective and less-toxic MMP inhibitors would be preferable (Overall and Lopez-Otín, 2002).
(C) Cyclines and Bisphosphonates
Conventional antimicrobial tetracyclines are commonly used in the treatment of bone resorption, as in rheumatoid arthritis (Lauhio et al., 1995) and periodontitis (Ryan et al., 1996), and non-antimicrobial chemically modified tetracyclines (CMTs) are currently being tested (Ramamurthy et al., 2002; Kivela-Rajamaki et al., 2003). These are among the few MMP inhibitors to be safe and effective, particularly after oral administration. CMTs inhibit both activity and secretion of MMPs and are thought to act through Ca2+ chelation (Golub et al., 1998). Tetracyclines and their semi-synthetic forms, doxicycline and minocycline, were shown to inhibit MMP-1, MMP-2, and MMP-12, both in vitro and in vivo.
To validate the role of MMPs in dentin caries progression, investigators have tested the effects of several MMP inhibitors—such as CMTs, zoledronate, and their combination—in vivo on young rats (Tjäderhane et al., 1999; Sulkala et al., 2001). These MMP inhibitors were administered per os for 7 wks, and, at the same time, the rats received a highly cariogenic diet associated with inoculation with a fresh suspension of Streptococcus sobrinus. The authors observed a decreased dentin caries progression in the animals treated with MMP inhibitors compared with controls. Moreover, all inhibitors used were significantly effective, but the inhibition intensity varied, with CMT-3, one of the most studied CMTs, demonstrating the most potent inhibition. Zoledronate, a third-generation bisphosphonate that inhibits MMP proteolytic activity without affecting synthesis (Boissier et al., 2000), also showed a reduced caries progression in dentin under fissures, but the combination CMT-3-zoledronate did not potentiate the effect. Based on promising pre-clinical studies and the generally mild side-effects, CMT-3 is currently being evaluated in clinical trials in cancer patients by oral administration (Acharya et al., 2004). Experiments are also under way to identify analogues of CMT-3 and other CMTs with better activity in terms of their specificity and in vivo efficacy in animal models, as described previously for the hydroxamate moieties (Gupta et al., 2003). These molecules may offer a very promising new class of drugs for inhibiting caries progression in dentin.
(D) Natural Therapies
The effects of naturally derived substances on MMP/TIMP balance have been recently studied for the treatment of several diseases. Avocado and soya bean unsaponifiables, which were shown to be effective in reducing articular pain (Henrotin et al., 2003), also demonstrated MMP-inhibiting properties in vitro (Kut et al., 1998). They were particularly effective in inhibiting IL-1ß-induced MMP-2, MMP-3, and TIMP-1 release by gingival fibroblasts. Oleic acid has also been shown to inhibit the activity of several MMPs, as well as the activation of MMP-3 by plasmin (Berton et al., 2001; Huet et al., 2004). It has been recently demonstrated in vitro that a natural substance extracted from seeds of Lupinus albus (LU105) was able to diminish the expression of both MMP-2 and MMP-9 by gingival fibroblasts derived from inflamed tissue, without modifying the amount of TIMP-2 expressed by these cells (Gaultier et al., 2003). TIMP-1 and MMP-1 were also significantly decreased. LU105 thus offers a good opportunity for the restoration of a correct balance between MMPs and their natural inhibitors in human inflamed gingiva in which the destruction of the ECM is likely to be largely due to host-derived MMPs. Puréed extract from elm cortex (Ulmi macrocarpa Hance) and its active ingredient, procyanidin oligomer, were also suggested as potential agents against periodontal diseases, since they were shown to exhibit potent inhibitory effects on both host-derived MMPs and the proteases of major periodontopathogens (Song et al., 2003).
The cancer-chemopreventive activity of green tea has been suggested by epidemiological studies (Mukhtar and Ahmad, 1999). Green tea polyphenols, especially epigallocatechin gallate (EGCG), were found to have potent and distinct inhibitory activity against MT1-MMP, resulting in the decrease of proMMP-2 activation. Furthermore, MMP-2 and MMP-9, as well as macrophage and neutrophil MMP-12 activities, were also directly inhibited by EGCG (Demeule et al., 2000; Garbisa et al., 2001; Sartor et al., 2002). The MMP-inhibitory effects of these natural substances suggest, therefore, that they could be effective in inhibiting dentin caries progression. Their lack of unwanted side-effects when compared with those of synthetic drugs makes them particularly attractive for the treatment of dentin caries, since they can be integrated into the daily-used topical products, such as toothpastes and mouthrinses, or by direct application, such as varnish.
To conclude, MMP inhibition by several inhibitors and particularly by natural substances could provide a potential therapeutic pathway to avoid caries progression in dentin once the role of MMPs in this process is firmly demonstrated. This review substantiates the need for further investigations in this domain.
Received February 2, 2005; Last revision June 14, 2005; Accepted August 2, 2005
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TOPABSTRACT(I) INTRODUCTION(II) REGULATION, STRUCTURE, AND...(III) THE DENTIN EXTRACELLULAR...(IV) THE DENTIN CARIES...(V) HOST-DERIVED MMPs FROM...(VI) HOST-DERIVED MMPs FROM...(VII) ACTIVATION OF MMPs...(VIII) MMP INHIBITORS AND...REFERENCES |
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Ahonen M, Ala-Aho R, Baker AH, George SJ, Grenman R, Saarialho-Kere U, et al. (2002). Antitumor activity and bystander effect of adenovirally delivered tissue inhibitor of metalloproteinases-3. Mol Ther 5:705–715.[ISI][Medline]
Anderson RS, Schwartz ER (1984). Phosphorylation of proteoglycans from human articular cartilage. Arthritis Rheum 27:58–71.[ISI][Medline]
Armstrong WG (1958). Further studies on the action of collagenase on sound and carious human dentin. J Dent Res 37:1001–1015.
Baba O, Qin C, Brunn JC, Jones JE, Wygant JN, McIntyre BW, et al. (2004). Detection of dentin sialoprotein in rat periodontium. Eur J Oral Sci 112:163–170.[ISI][Medline]
Baker AH, George SJ, Zaltsman AB, Murphy G, Newby AC (1999). Inhibition of invasion and induction of apoptotic cell death of cancer cell lines by overexpression of TIMP-3. Br J Cancer 79:1347–1355.[ISI][Medline]
Baker AH, Edwards DR, Murphy G (2002). Metalloproteinase inhibitors: biological actions and therapeutic opportunities. J Cell Sci 115:3719–3727.
Bellahcene A, Merville MP, Castronovo V (1994). Expression of bone sialoprotein, a bone matrix protein, in human breast cancer. Cancer Res 54:2823–2826.
Bellahcene A, Antoine N, Clausse N, Tagliabue E, Fisher LW, Kerr JM, et al. (1996). Detection of bone sialoprotein in human breast cancer tissue and cell lines at both protein and messenger ribonucleic acid levels. Lab Invest 75:203–210.[ISI][Medline]
Berton A, Rigot V, Huet E, Decarme M, Eeckhout Y, Patthy L, et al. (2001). Involvement of fibronectin type II repeats in the efficient inhibition of gelatinases A and B by long-chain unsaturated fatty acids. J Biol Chem 276:20458–20465.
Birkedal-Hansen H (1993). Role of matrix metalloproteinases in human periodontal diseases. J Periodontol 64:474–484.[ISI][Medline]
Birkedal-Hansen H, Moore WG, Bodden MK, Windsor LJ, Birkedal-Hansen B, DeCarlo A, et al. (1993). Matrix metalloproteinases: a review. Crit Rev Oral Biol Med 4:197–250.
Bode W, Fernandez-Catalan C, Tschesche H, Grams F, Nagase H, Maskos K (1999). Structural properties of matrix metalloproteinases. Cell Mol Life Sci 55:639–652.[ISI][Medline]
Boissier S, Ferreras M, Peyruchaud O, Magnetto S, Ebetino FH, Colombel M, et al. (2000). Bisphosphonates inhibit breast and prostate carcinoma cell invasion, an early event in the formation of bone metastases. Cancer Res 60:2949–2954.
Bourd-Boittin K, Septier D, Hall R, Goldberg M, Menashi S (2004). Immunolocalization of enamelysin (matrix metalloproteinase-20) in the forming rat incisor. J Histochem Cytochem 52:437–445.
Bourd-Boittin K, Fridman R, Fanchon S, Septier D, Goldberg M, Menashi S (2005). Matrix metalloproteinase inhibition impairs the processing, formation and mineralization of dental tissues during mouse molar development. Exp Cell Res 304:493–505.[ISI][Medline]
Bramhall SR, Schulz J, Nemunaitis J, Brown PD, Baillet M, Buckels JA (2002). A double-blind placebo-controlled, randomised study comparing gemcitabine and marimastat with gemcitabine and placebo as first line therapy in patients with advanced pancreatic cancer. Br J Cancer 87:161–167.[ISI][Medline]
Brinckerhoff CE, Matrisian LM (2002). Matrix metalloproteinases: a tail of a frog that became a prince. Nat Rev Mol Cell Biol 3:207–214.[ISI][Medline]
Butler WT, Ritchie H (1995). The nature and functional significance of dentin extracellular matrix proteins. Int J Dev Biol 39:169–179.[ISI][Medline]
Caron C, Xue J, Bartlett JD (1998). Expression and localization of membrane type 1 matrix metalloproteinase in tooth tissues. Matrix Biol 17:501–511.[ISI][Medline]
Caron C, Xue J, Sun X, Simmer JP, Bartlett JD (2001). Gelatinase A (MMP-2) in developing tooth tissues and amelogenin hydrolysis. J Dent Res 80:1660–1664.
Caufield PW, Griffen AL (2000). Dental caries. An infectious and transmissible disease. Pediatr Clin North Am 47:1001–1019.[ISI][Medline]
Davis GE (1991). Identification of an abundant latent 94-kDa gelatin-degrading metalloprotease in human saliva which is activated by acid exposure: implications for a role in digestion of collagenous proteins. Arch Biochem Biophys 286:551–554.[ISI][Medline]
Dayan D, Binderman I, Mechanic GL (1983). A preliminary study of activation of collagenase in carious human dentine matrix. Arch Oral Biol 28:185–187.[ISI][Medline]
Demeule M, Brossard M, Page M, Gingras D, Beliveau R (2000). Matrix metalloproteinase inhibition by green tea catechins. Biochim Biophys Acta 1478:51–60.[Medline]
Drouin L, Overall CM, Sodek J (1988). Identification of matrix metalloendo-proteinase inhibitor (TIMP) in human parotid and submandibular saliva: partial purification and characterization. J Periodontal Res 23:370–377.[ISI][Medline]
Ducy P, Desbois C, Boyce B, Pinero G, Story B, Dunstan C, et al. (1996). Increased bone formation in osteocalcin-deficient mice. Nature 382:448–452.[Medline]
Dumas J, Hurion N, Weill R, Keil B (1985). Collagenase in mineralized tissues of human teeth. FEBS Lett 187:51–55.[ISI][Medline]
Dung SZ, Gregory RL, Li Y, Stookey GK (1995). Effect of lactic acid and proteolytic enzymes on the release of organic matrix components from human root dentin. Caries Res 29:483–489.[ISI][Medline]
Ekstrand KR, Ricketts DN, Kidd EA (2001). Occlusal caries: pathology, diagnosis and logical management. Dent Update 28:380–387.[Medline]
Eley BM, Cox SW (1992). Cathepsin B/L-, elastase-, tryptase-, trypsin- and dipeptidyl peptidase IV-like activities in gingival crevicular fluid: correlation with clinical parameters in untreated chronic periodontitis patients. J Periodontal Res 27:62–69.[ISI][Medline]
Embery G, Hall R, Waddington R, Septier D, Goldberg M (2001). Proteoglycans in dentinogenesis. Crit Rev Oral Biol Med 12:331–349.[Abstract]
Evans JD, Stark A, Johnson CD, Daniel F, Carmichael J, Buckels J, et al. (2001). A phase II trial of marimastat in advanced pancreatic cancer. Br J Cancer 85:1865–1870.[ISI][Medline]
Fanchon S, Bourd K, Septier D, Everts V, Beertsen W, Menashi S, et al. (2004). Involvement of matrix metalloproteinases in the onset of dentin mineralization. Eur J Oral Sci 112:171–176.[ISI][Medline]
Farges JC, Romeas A, Melin M, Pin JJ, Lebecque S, Lucchini M, et al. (2003). TGF-beta1 induces accumulation of dendritic cells in the odontoblast layer. J Dent Res 82:652–656.
Featherstone JD (2004). The continuum of dental caries—evidence for a dynamic disease process. J Dent Res 83(Spec Iss C):C39–C42.
Fedarko NS, Jain A, Karadag A, Van Eman MR, Fisher LW (2001). Elevated serum bone sialoprotein and osteopontin in colon, breast, prostate, and lung cancer. Clin Cancer Res 7:4060–4066.
Fedarko NS, Jain A, Karadag A, Fisher LW (2004). Three small integrin binding ligand N-linked glycoproteins (SIBLINGs) bind and activate specific matrix metalloproteinases. FASEB J 18:734–736.
Fincham AG, Moradian-Oldak J, Simmer JP (1999). The structural biology of the developing dental enamel matrix. J Struct Biol 126:270–299.[ISI][Medline]
Finkelman RD, Mohan S, Jennings JC, Taylor AK, Jepsen S, Baylink DJ (1990). Quantitation of growth factors IGF-I, SGF/IGF-II, and TGF-beta in human dentin. J Bone Miner Res 5:717–723.[ISI][Medline]
Fisher LW, Fedarko NS (2003). Six genes expressed in bones and teeth encode the current members of the SIBLING family of proteins. Connect Tissue Res 44(Suppl 1):33–40.[Medline]
Garbisa S, Sartor L, Biggin S, Salvato B, Benelli R, Albini A (2001). Tumor gelatinases and invasion inhibited by the green tea flavanol epigallocatechin-3-gallate. Cancer 91:822–832.[ISI][Medline]
Gaultier F, Foucault-Bertaud A, Lamy E, Ejeil AL, Dridi SM, Piccardi N, et al. (2003). Effects of a vegetable extract from Lupinus albus (LU105) on the production of matrix metalloproteinases (MMP1, MMP2, MMP9) and tissue inhibitor of metalloproteinases (TIMP1, TIMP2) by human gingival fibroblasts in culture. Clin Oral Investig 7:198–205.[Medline]
George SJ (2000). Therapeutic potential of matrix metalloproteinase inhibitors in atherosclerosis. Expert Opin Investig Drugs 9:993–1007.[ISI][Medline]
Goldberg M, Boskey AL (1996). Lipids and biomineralizations. Prog Histochem Cytochem 31:1–187.[ISI][Medline]
Goldberg M, Keil B (1989). Action of a bacterial Achromobacter collagenase on the soft carious dentine: an in vitro study with the scanning electron microscope. J Biol Buccale 17:269–274.[ISI][Medline]
Goldberg M, Septier D, Bourd K, Hall R, George A, Goldberg H, et al. (2003a). Immunohistochemical localization of MMP-2, MMP-9, TIMP-1, and TIMP-2 in the forming rat incisor. Connect Tissue Res 44:143–153.[ISI][Medline]
Goldberg M, Rapoport O, Septier D, Palmier K, Hall R, Embery G, et al. (2003b). Proteoglycans in predentin: the last 15 micrometers before mineralization. Connect Tissue Res 44(Suppl 1):184–188.[Medline]
Golub LM, Lee HM, Ryan ME, Giannobile WV, Payne J, Sorsa T (1998). Tetracyclines inhibit connective tissue breakdown by multiple non-antimicrobial mechanisms. Adv Dent Res 12:12–26.
Gunja-Smith Z, Woessner JF Jr (1993). Activation of cartilage stromelysin-1 at acid pH and its relation to enzyme pH optimum and osteoarthritis. Agents Actions 40:228–231.[ISI][Medline]
Gupta SP, Maheswaran V, Pande V, Kumar D (2003). A comparative QSAR study on carbonic anhydrase and matrix metalloproteinase inhibition by sulfonylated amino acid hydroxamates. J Enzyme Inhib Med Chem 18:7–13.[ISI][Medline]
Hall R, Septier D, Embery G, Goldberg M (1999). Stromelysin-1 (MMP-3) in forming enamel and predentine in rat incisor-coordinated distribution with proteoglycans suggests a functional role. Histochem J 31:761–770.[ISI][Medline]
Heikinheimo K, Salo T (1995). Expression of basement membrane type IV collagen and type IV collagenases (MMP-2 and MMP-9) in human fetal teeth. J Dent Res 74:1226–1234.
Henrotin YE, Sanchez C, Deberg MA, Piccardi N, Guillou GB, Msika P, et al. (2003). Avocado/soybean unsaponifiables increase aggrecan synthesis and reduce catabolic and proinflammatory mediator production by human osteoarthritic chondrocytes. J Rheumatol 30:1825–1834.[ISI][Medline]
Huet E, Cauchard JH, Berton A, Robinet A, Decarme M, Hornebeck W, et al. (2004). Inhibition of plasmin-mediated prostromelysin-1 activation by interaction of long chain unsaturated fatty acids with kringle 5. Biochem Pharmacol 67:643–654.[ISI][Medline]
Iijima K, Ando K, Kishi M, Nakashizuka T, Hayakawa T (1983). Collagenase activity in human saliva. J Dent Res 62:709–712.
Ingman T, Sorsa T, Lindy O, Koski H, Konttinen YT (1994). Multiple forms of gelatinases/type IV collagenases in saliva and gingival crevicular fluid of periodontitis patients. J Clin Periodontol 21:26–31.[ISI][Medline]
Ingman T, Tervahartiala T, Ding Y, Tschesche H, Haerian A, Kinane DF, et al. (1996). Matrix metalloproteinases and their inhibitors in gingival crevicular fluid and saliva of periodontitis patients. J Clin Periodontol 23:1127–1132.[ISI][Medline]
Karsdal MA, Larsen L, Engsig MT, Lou H, Ferreras M, Lochter A, et al. (2002). Matrix metalloproteinase-dependent activation of latent transforming growth factor-beta controls the conversion of osteoblasts into osteocytes by blocking osteoblast apoptosis. J Biol Chem 277:44061–44067.
Katz S, Park KK, Palenik CJ (1987). In-vitro root surface caries studies. J Oral Med 42:40–48.[Medline]
Kawasaki K, Featherstone JD (1997). Effects of collagenase on root demineralization. J Dent Res 76:588–595.
Kinoshita Y (1979). Incorporation of serum albumin into the developing dentine and enamel matrix in the rabbit incisor. Calcif Tissue Int 29:41–46.[ISI][Medline]
Kivela-Rajamaki M, Maisi P, Srinivas R, Tervahartiala T, Teronen O, Husa V, et al. (2003). Levels and molecular forms of MMP-7 (matrilysin-1) and MMP-8 (collagenase-2) in diseased human peri-implant sulcular fluid. J Periodontal Res 38:583–590.[ISI][Medline]
Knott L, Bailey A (2000). Collagen cross-links in mineralized tissues: a role for the pyrrole cross-link. In: Chemistry and biology of mineralized tissues. Goldberg M, Boskey A, Robinson C, eds. Rosemont, IL: American Academy of Orthopaedic Surgeons, pp. 125–128.
Kut C, Assoumou A, Dridi M, Bonnefoix M, Gogly B, Pellat B, et al. (1998). Morphometric analysis of human gingival elastic fibres degradation by human leukocyte elastase protective effect of avocado and soybean unsaponifiables (ASU). Pathol Biol 46:571–576.[Medline]
Lauhio A, Salo T, Tjäderhane L, Lahdevirta J, Golub LM, Sorsa T (1995). Tetracyclines in treatment of rheumatoid arthritis. Lancet 346:645–646.[ISI][Medline]
Loesche WJ (1986). Role of Streptococcus mutans in human dental decay. Microbiol Rev 50:353–380.
Lynch CC, Matrisian LM (2002). Matrix metalloproteinases in tumor-host cell communication. Differentiation 70:561–573.[ISI][Medline]
MacDougall M (1998). Refined mapping of the human dentin sialophosphoprotein (DSPP) gene within the critical dentinogenesis imperfecta type II and dentin dysplasia type II loci. Eur J Oral Sci 106(Suppl 1):227–233.[Medline]
MacDougall M, Gu TT, Simmons D (1996). Dentin matrix protein-1, a candidate gene for dentinogenesis imperfecta. Connect Tissue Res 35:267–272.[Medline]
Makela M, Salo T, Uitto VJ, Larjava H (1994). Matrix metalloproteinases (MMP-2 and MMP-9) of the oral cavity: cellular origin and relationship to periodontal status. J Dent Res 73:1397–1406.
Marsh PD (1999). Microbiologic aspects of dental plaque and dental caries. Dent Clin North Am 43:599–614.[Medline]
McCawley LJ, Matrisian LM (2001). Matrix metalloproteinases: they’re not just for matrix anymore! Curr Opin Cell Biol 13:534–540.[ISI]
