Expression of MMP-8 and MMP-13 mRNAs in rat periodontium during tooth eruption

Effects of a 2-Year Early Childhood Vitamin D3 Intervention on Tooth Enamel and Oral Health at Age 6-7 Years

INTRODUCTION

The aim of the study was to compare the effects of a 30 µg/day versus 10 µg/day vitamin D supplementation, given during the two first years of life, on oral health at the age of six to 7 years.

METHODS

In 2013-2016, we conducted a randomized, double-blinded, clinical trial from age 2 weeks to 2 years of daily vitamin D3 supplementation (10 vs. 30 µg), including 975 healthy infants. For the present follow-up study at age 6-7 years, a sample of 123 children underwent oral examination by investigators blinded to the intervention group. Tooth enamel defect and caries findings, oral rinse active matrix metalloproteinase-8 levels, and tooth eruption were recorded. The intervention groups were compared with χ2 and Mann-Whitney U tests. Associations of the oral health outcomes were evaluated with correlation analysis and logistic regression.

RESULTS

Of the children (median age 7.4 years, 51% boys), 56% belonged to the 30 µg intervention group. Developmental defect of enamel (DDE) was found in 39% of the children in the 10 µg intervention group and in 53% of the 30 µg group (p = 0.104). In total, 94% of children were vitamin D sufficient (25[OH]D ≥50 nmol/L) and 88% had caries-free teeth. No associations were found between vitamin D intervention group in infancy and oral health or the presence of DDE.

CONCLUSION

Daily supplementation with 10 µg vitamin D3 in the Northern Hemisphere seems adequate in healthy children younger than 2 years in ensuring good oral health at early school age.

Runx2 and Nell-1 in dental follicle progenitor cells regulate bone remodeling and tooth eruption

Dental follicles are necessary for tooth eruption, surround the enamel organ and dental papilla, and regulate both the formation and resorption of alveolar bone. Dental follicle progenitor cells (DFPCs), which are stem cells found in dental follicles, differentiate into different kinds of cells that are necessary for tooth formation and eruption. Runt‐related transcription factor 2 (Runx2) is a transcription factor that is essential for osteoblasts and osteoclasts differentiation, as well as bone remodeling. Mutation of Runx2 causing cleidocranial dysplasia negatively affects osteogenesis and the osteoclastic ability of dental follicles, resulting in tooth eruption difficulties. Among a variety of cells and molecules, Nel-like molecule type 1 (Nell-1) plays an important role in neural crest-derived tissues and is strongly expressed in dental follicles. Nell-1 was originally identified in pathologically fused and fusing sutures of patients with unilateral coronal synostosis, and it plays indispensable roles in bone remodeling, including roles in osteoblast differentiation, bone formation and regeneration, craniofacial skeleton development, and the differentiation of many kinds of stem cells. Runx2 was proven to directly target the Nell-1 gene and regulate its expression. These studies suggested that Runx2/Nell-1 axis may play an important role in the process of tooth eruption by affecting DFPCs. Studies on short and long regulatory noncoding RNAs have revealed the complexity of RNA-mediated regulation of gene expression at the posttranscriptional level. This ceRNA network participates in the regulation of Runx2 and Nell-1 gene expression in a complex way. However, non-study indicated the potential connection between Runx2 and Nell-1, and further researches are still needed.

Correlation between Peri-Implant Marginal Bone Loss Progression and Peri-Implant Sulcular Fluid Levels of Metalloproteinase-8

Objectives: The aim of this retrospective study was to analyze peri-implant marginal bone loss levels/rates and peri-implant sulcular fluid levels/rates of metalloproteinase-8 in three timeframes (6 months post-surgery—restoration delivery (T0)—and 6 (T6) and 24 (T24)-months post-loading) and to evaluate if there is a correlation between peri-implant sulcular fluid levels of metalloproteinase-8 and peri-implant marginal bone loss progression. Materials and Methods: Two cohorts of patients undergoing implant surgery between January 2017 and January 2019 were selected in this retrospective study. A total of 39 patients received 39 implants with a laser-microtextured collar surface, and 41 subjects received 41 implants with a machined/smooth surface. For each patient, periapical radiographs and a software package were used to measure marginal bone loss rates. Implant fluid samples were analyzed by an enzyme-linked immunosorbent assay (ELISA) test. The modified plaque index, probing depth, and bleeding on probing were also recorded. Results: High marginal bone rates at T24 were strongly associated with elevated rates between T0 and T6. The levels of metalloproteinase-8 were significantly more elevated around implants with marginal bone loss, in relation to implants without marginal bone loss. Marginal bone loss (MBL) rates at 24 months were associated with initial bone loss rates and initial levels of metalloproteinase-8. Conclusions: Peri-implant marginal bone loss progression is statistically correlated to peri-implant sulcular fluid levels of metalloproteinase-8. Moreover, the initial high levels of marginal bone loss and metalloproteinase-8 can be considered as indicators of the subsequent progression of peri-implant MBL: implants with increased marginal bone loss rates and metalloproteinase-8 levels at 6 months after loading are likely to achieve additional marginal bone loss values.

Effects of sodium chloride on the gene expression profile of periodontal ligament fibroblasts during tensile strain

Purpose

During orthodontic tooth movement, pressure and tension zones develop in the periodontal ligament, and periodontal ligament fibroblasts (PDLF) become exposed to mechanical strain. Enhanced salt (NaCl) concentrations are known to modulate responses of PDLF and immune cells to different stimuli like mechanical strain. Here, we investigated the impact of tensile strain on the gene expression profile of PDLF under normal (NS) and high salt (HS) conditions.

Methods

After preincubation under NS or HS (+40 mM NaCl in medium) conditions for 24 h, PDLF were stretched 16% for 48 h using custom-made spherical cap silicone stamps using an established and published setup. After determination of cell number and cytotoxicity, we analyzed expression of genes involved in extracellular matrix reorganization, angiogenesis, bone remodeling, and inflammation by quantitative real-time polymerase chain reaction (RT-qPCR).

Results

Tensile strain did not affect the expression of genes involved in angiogenesis or extracellular matrix reorganization by PDLF, which however modulate inflammatory responses and bone remodeling in reaction to 16% static tensile strain. Salt (NaCl) treatment triggered enhanced extracellular matrix formation, expression of cyclooxygenase 2 and bone metabolism in PDLF during tensile strain.

Conclusions

Salt (NaCl) consumption may influence orthodontic tooth movement and periodontal bone loss via modulation of extracellular matrix and bone metabolism. Excessive salt intake during orthodontic therapy may cause adverse effects regarding periodontal inflammation and bone resorption.

Effects of Compressive and Tensile Strain on Macrophages during Simulated Orthodontic Tooth Movement

During orthodontic tooth movement (OTM) to therapeutically correct the position of misaligned teeth, thus improving oral health and quality of life, fibroblasts, macrophages, and other immune cells within the periodontal ligament (PDL), which connects a tooth to its surrounding bone, are exposed to compressive and tensile strain. While it is known that PDL fibroblasts are critically involved in the biological regulation of OTM by a mechanotransductively triggered release of cytokines, it is unclear whether macrophages also react to pressure and tension in a similar manner thus impacting on or mediating OTM. RAW264.7 macrophages were seeded onto conventional 6-well cell culture plates for pressure or on Bioflex plates for tension assays and preincubated for 24 h. For in vitro simulation of physiological orthodontic compressive or tensile strain for 2 h, 4 h, 24 h, and 48 h, glass discs (2 g/cm²) were placed or adherent macrophages isotropically stretched for 16%, respectively. We determined cell number, cytotoxicity, and gene/protein expression of Vegf-a/VEGF-A (macrophage-mediated angiogenesis), Mmp-8/9 (extracellular matrix reorganization), and Cox-2/PG-E2, Il-6/IL-6, and Tnf-α/TNF-α (proinflammatory mediators) by RT-qPCR and ELISA. Compressive but not tensile strain resulted in a significant reduction in cell number after only 2 h. Mmp-8 and Mmp-9 expression was significantly enhanced within 24 h of compressive and in part tensile strain. Significantly increased Vegf-a/VEGF-A expression was detected within 4 h of pressure, but not during application of tensile strain. Expression of proinflammatory mediators Cox-2/PG-E2, Il-6/IL-6, and Tnf-α/TNF-α was significantly increased as early as 2-4 h after application of compressive or tensile strain. Our results indicate that macrophages respond early on to compressive and tensile strain occurring during OTM with an enhanced gene expression of proinflammatory cytokines, which could affect PDL fibroblasts, osteoblasts, and immune cells triggering or enhancing the biological mechanisms and osteoclastogenesis underlying OTM.

Association Between Genetic Polymorphisms in Metaloproteinases of the Matrix and Delayed Tooth Emergence: A Cross-sectional Study

Background and Aims:

Animal models have been demonstrating that MMPs have an important function in the tooth eruption process. The aim of this study was to evaluate the association between genetic polymorphisms in MMP8 and MMP13 and delayed tooth eruption of permanent teeth.

Materials and Methods:

This cross-sectional study selected 216 children, 9- to 12-year-old, from public schools at Manaus, Amazonas, Brazil. During oral clinical examination, each permanent tooth emerged in the oral cavity was evaluated. Children were considered with delayed tooth eruption when at least one permanent tooth was delayed and were classified in 2 groups: children “with delayed tooth emergency” and “without delayed tooth emergency.” Saliva samples were collected from DNA extraction. The genetic polymorphisms rs17099443 and rs3765620 in MMP8, and rs478927 and rs2252070 in MMP13 were genotyped.

Statistical Analysis:

PLINK V1.07 ( http://pngu.mgh.harvard.edu/purcell/plink/ ) and GraphPad Prism 5.0 (San Diego, CA, USA) were used. The c2 or Fisher exact test was used to calculate genotypes and alleles distributions. To compare the mean number of delayed teeth according to genotypes, the Kruskal-Wallis test with multiple comparison Dunn test was used. The established alpha for all comparisons was .05.

Results:

The polymorphism rs17099443 in MMP8 was associated with delayed tooth eruption in the genotype distribution ( P = .05). In the allele distribution, the C allele was underrepresented in children with delayed tooth eruption ( P = .01; OR = 0.61, 95% confidence interval, 0.41–0.9).

Conclusion:

The genetic polymorphism rs17099443 in MMP8 is associated with delayed tooth eruption.

Degradation of extracellular matrices propagates calcification during development and healing in bones and teeth

BACKGROUND

Bone, dentin, and enamel are tissues formed through calcification, a process involving deposition of calcium phosphate minerals on extracellular organic matrices. Calcification, the underlying mechanism of which is unknown, is initiated with mineral deposition followed by advancing of the deposit and subsequent maturation of the mineral crystal.

HIGHLIGHT

We have reviewed the current knowledge of how calcification proceeds during bone development, bone healing, and enamel and dentin development, based on reported studies. Previous studies reported by us and by other authors have suggested that degradation of some extracellular matrix (ECM) proteins is involved in calcification during bone and dentin development and bone healing in a manner similar to that previously reported for enamel development.

CONCLUSION

The ECM proteins may inhibit mineral deposition and calcification, similar to the role of amelogenin during enamel development. The candidates for the amelogenin equivalents in bone and dentin have not been identified. Further studies are required to elucidate the regulatory mechanisms of bone and dentin calcification in light of specific ECM proteins that prevent calcification and enzymes that degrade these ECM proteins.

Sodium-chloride-induced effects on the expression profile of human periodontal ligament fibroblasts with focus on simulated orthodontic tooth movement

Increased salt (NaCl) consumption triggers chronic diseases such as hypertension or osteopenia. Its impact on orthodontic tooth movement and periodontitis, however, has not been investigated, although both processes are related to the immune system, with periodontal ligament fibroblasts (PDLFs) playing a key mediating role. Here, we investigated the impact of NaCl on the expression pattern of PDLFs in a model of simulated compressive orthodontic strain. Periodontal ligament fibroblasts were preincubated for 24 h with additional 0 or 40 mM NaCl and concurrently treated for another 48 h with or without compressive strain of 2 g cm^-2 . We analyzed the expression of genes and proteins involved in orthodontic tooth movement by reverse transcription quantitative polymerase chain reaction (RT-qPCR), ELISA, and immunoblot. Co-culture experiments were performed to observe PDLF-mediated osteoclastogenesis. A higher (40 mM) concentration of NaCl in the culture medium resulted in increased secretion of prostaglandin, expression of alkaline phosphatase, and expression of genes involved in extracellular matrix remodeling, but decreased compression-induced expression of the interleukin-6 (IL6) gene. The 40 mM concentration of NaCl also enhanced receptor activator of nuclear factor kappa-B ligand (RANKL) but reduced that of osteoprotegerin (OPG), resulting in upregulated PDLF-mediated osteoclastogenesis. A high NaCl concentration in the periodontal ligament, corresponding to a high-salt diet in vivo, may influence orthodontic tooth movement and periodontitis through increased secretion of prostaglandins by PDLFs and upregulated PDLF-mediated osteoclastogenesis, possibly accelerating orthodontic tooth movement and propagating periodontitis and periodontal bone loss.

Expression kinetics of human periodontal ligament fibroblasts in the early phases of orthodontic tooth movement

PURPOSE

Human periodontal ligament (hPDL) fibroblasts play a crucial mediating role in orthodontic tooth movement (OTM). In this study, we investigated the expression kinetics of genes associated with OTM in its early phase to obtain better insight into the timing and regulation of molecular and cellular signalling and transformation processes occurring in compressive areas of the periodontal ligament during OTM.

METHODS

Adherent hPDL fibroblasts were stimulated with physiological orthodontic compressive forces of 2 g/cm² for 24, 48, 72, and 96 h under cell culture conditions. At each time point, we quantified relative gene expression of genes involved in bone remodelling (ALPL), inflammation (COX2, IL-6), extracellular matrix reorganization (COL1A2, P4HA1, FN1, MMP8) and angiogenesis (VEGF-A) by means of RT-qPCR as well as protein expression of osteoclastogenesis-regulating RANK-L and OPG relative to pressure-untreated controls incubated for corresponding time periods. In addition, coculture experiments with osteoclast precursor cells were performed to determine the extent of hPDL-fibroblast-mediated osteoclastogenesis (TRAP staining).

RESULTS

As primary response to compressive forces within 24 h, we observed an induction of genes associated with angiogenesis, inflammation, osteoblastogenesis, and the remodelling of the extracellular matrix, with RANK-L expression at first slightly inhibited and only increased after 48 h. Major hPDL-mediated osteoclastogenesis was observed after 72 h with minor, non-RANK-L-dependent osteoclastogenesis occurring as early as 24 h after compressive force application.

CONCLUSIONS

hPDL fibroblasts seem to play a major mediating role in the early phase of OTM with a differentiated, time-dependent regulation and expression pattern of cytokines and other mediators.

Analysis of calcium, phosphorus, and carbon concentrations during developmental calcification of dentin and enamel in rat incisors using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX)

OBJECTIVE

The study was designed to investigate the concentrations of calcium (Ca), phosphorus (P), and carbon (C) during developmental calcification of dentin and enamel in rat incisors.

METHODS

Mandibular incisors from eight 2-week-old male Wistar rats were analyzed by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). We analyzed data on the elements in the course of developmental processes in dentin and enamel and along the vertical line of the matrix between odontoblasts and ameloblasts.

RESULTS

The dentin concentrations of Ca and P and the Ca/P ratio were the lowest, while the C concentration was the highest in initial dentin. The Ca and P concentrations were the lowest, whereas the C concentration was the highest in predentin along the vertical line; the Ca/P ratio did not show any differences. The concentrations of Ca and P increased, while the C concentration decreased during early maturation and more so in late maturation in developing enamel, while the Ca/P ratio increased during late maturation. The Ca and P concentrations and the Ca/P ratio were the highest, while the C concentration was the lowest in enamel adjacent to the junction with dentin on the vertical line.

CONCLUSIONS

During tooth development, the initial dentin matrix may possess distinctive mineral characteristics as compared with other parts of dentin and predentin. Elemental composition of the mineral in enamel may change during late maturation. Our results are suggestive of degradation of organic components during developmental calcification in dentin and enamel.

Association between genetic polymorphisms of MMP8 and the risk of steroid-induced osteonecrosis of the femoral head in the population of northern China

BACKGROUND

Steroid-induced osteonecrosis of the femoral head (ONFH) is the most common clinical nontraumatic ONFH. Once ONFH occurs, it seriously reduces patients' quality of life. The matrix metalloproteinase/tissue inhibitor of metalloproteinase (MMP/TIMP) system was found to play a significant role in the development of ONFH. The aim of this study was to identify the associations between 7 genes selected from the MMP/TIMP system and steroid-induced ONFH.

METHODS

We genotyped 34 single-nucleotide polymorphisms (SNPs) of 7 genes selected from the MMP/TIMP system in a case-control study with 285 cases of steroid-induced ONFH and 308 healthy controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using the chi-squared test, genetic model analysis, haplotype analysis, and stratification analysis.

RESULTS

We found that the minor alleles of rs1940475 and rs11225395 in MMP8 were associated with a 1.32-fold increased risk of steroid-induced ONFH in the allelic model analysis (P = 0.021 and 0.022, respectively). In the genetic model analysis, we found that rs3740938, rs2012390, rs1940475, and rs11225395 were associated with an increased risk of steroid-induced ONFH. In further stratification analysis, rs3740938 and rs2012390 displayed a significantly increased risk of steroid-induced ONFH in females under the dominant (rs3740938, OR = 2.69, 95% CI: 1.50-4.83, P = 0.001; rs2012390, OR = 2.30, 95% CI: 1.31-4.03, P = 0.012) and additive (rs3740938, OR = 2.02, 95% CI: 1.24-3.29, P = 0.010; rs2012390, OR = 1.77, 95% CI: 1.12-2.80, P = 0.047) models. In addition, haplotype "AGTCA" of MMP8 was found to be associated with a 1.40-fold increased risk of steroid-induced ONFH (95% CI: 1.04-1.88, P = 0.025).

CONCLUSION

Our results verify that genetic variants of MMP8 contribute to steroid-induced ONFH susceptibility in the population of northern China. In addition, we found that gender differences might interact with MMP8 polymorphisms to contribute to the overall susceptibility to steroid-induced ONFH.

Expression of inflammatory cytokines and MMPs on replanted teeth at different extra-alveolar time: an ex vivo and in vivo study

BACKGROUND

Immediately after the avulsed tooth is replanted, a complex inflammatory response ensues. As part of the periodontium healing process, the extracellular matrix macromolecules are essential to create the cellular environment required during healing and morphogenesis.

AIM

This study was designed to evaluate the correlation between different extra-alveolar dry times and inflammatory cytokines and matrix metalloproteinases (MMPs) as part of the periodontal ligament (PDL) gene expression.

DESIGN

The first phase of the study aimed testing human PDL cells ex vivo. Extracted teeth were dried for 15 and 30 min. The PDL cells were extracted and analyzed by qRT-PCR. The second phase was performed in vivo, and 36 Sprague Dawley rat first maxillary molars were extracted and replanted after 15, 30, and 60 min extra-alveolar time. We tested the levels of inflammatory cytokines and MMPS in periodontal tissue at 3, 7, and 28 days after tooth replantation. The replanted area was dissected, grounded, and analyzed by RT-PCR.

RESULTS

Expressions of IL-1β, IL-6, TNF-α, and MMP-3 and MMP-9 were significantly higher in the replanted teeth. Extended dry time had a direct correlation with induction of pro-inflammatory cytokine and MMPs in PDL cells.

CONCLUSION

Our study showed that pro-inflammatory cytokines were more significantly expressed in the tissues surrounding the replanted teeth. Future research must be undertaken to additionally confirm the release of these cytokines and be focused on the inhibition of these cytokines to reduce inflammation of replanted teeth.

MMP-8 Is Critical for Dexamethasone Therapy in Alkali-Burned Corneas Under Dry Eye Conditions

Our previous studies have shown that Dexamethasone (Dex) reduced the expression of matrix-metalloproteinases (MMPs -1,-3,-9,-13), IL-1β and IL-6, while it significantly increased MMP-8 mRNA transcripts in a concomitant dry eye and corneal alkali burn murine model (CM). To investigate if MMP-8 induction is responsible for some of the protective effects of Dex in CM, MMP-8 knock out mice (MMP-8KO) were subjected to the CM for 2 or 5 days and topically treated either with 2 μl of 0.1% Dexamethasone (Dex), or saline QID. A separate group of C57BL/6 mice were topically treated with Dex or BSS and received either 100 nM CAM12 (MMP-8 inhibitor) or vehicle IP, QD. Here we demonstrate that topical Dex treated MMP-8KO mice subjected to CM showed reduced corneal clarity, increased expression of inflammatory mediators (IL-6, CXCL1, and MMP-1 mRNA) and increased neutrophil infiltration at 2D and 5D compared to Dex treated WT mice. C57BL/6 mice topically treated with Dex and CAM12 IP recapitulated findings seen with MMP-8KO mice. These results suggest that some of the anti-inflammatory effects of Dex are mediated through increased MMP-8 expression. J. Cell. Physiol. 231: 2506-2516, 2016. © 2016 Wiley Periodicals, Inc.

Dental Follicle Cells Participate in Tooth Eruption via the RUNX2-MiR-31-SATB2 Loop

Cleidocranial dysplasia (CCD) is characterized by the runt-related transcription factor 2 (RUNX2) mutation, which results in delayed tooth eruption due to disturbed functions of dental follicle. Accumulating evidence has revealed a key regulatory circuit, including RUNX2, miR-31, and special AT-rich binding protein 2 (SATB2) acting in concert in mesenchymal stem cell homeostasis and functions. However, whether such a regulatory loop works in dental follicle cells (DFCs) remains unknown. Herein, we investigated the roles of RUNX2-miR-31-SATB2 in DFCs from patients with CCD (DFCs-CCD) to advance our understanding regarding physical tooth eruption. We identified a novel mutation on exon 5 (c.634T>G, p.T212P) in RUNX2 via exome sequencing in the CCD patient with typical clinical presentations. Compared with DFCs from healthy donors, DFCs-CCD displayed significantly lower osteogenic, osteoclast-inductive, and matrix-degrading capacities and had lower RUNX2 (a transcriptional inhibitor of miR-31), higher miR-31, and downregulated SATB2. Lower ratios of RANKL/OPG and RANKL/RANK, as well as decreased expression of matrix metalloproteinase 9 (MMP9) and matrix metalloproteinase 2 (MMP2), would lead to inactivation of osteoclasts and suppression of bone matrix remodeling in DFCs-CCD. Furthermore, the roles of the RUNX2-miR-31-SATB2 loop in DFCs-CCD were revealed by endogenous miR-31 knockdown, which resulted in increased SATB2 and RUNX2, as well as osteoclast-inductive and matrix degradation capacities. Conversely, SATB2, RUNX2, MMP9, MMP2, and osteoclast-inductive factors expression declined upon ectopic miR-31 overexpression in normal DFCs. Importantly, neonatal mice with in vivo siRUNX2 delivery exhibited less activated osteoclasts around dental follicles and delayed tooth eruption. Together, these results suggest that RUNX2 mutation/haploinsufficiency disturbs osteoclast-inductive signaling in DFCs, which may be responsible for delayed tooth eruption in CCD patients. Manipulation of the RUNX2-miR-31-SATB2 loop may be a potential way to facilitate tooth eruption in CCD patients.

α11β1 integrin-mediated MMP-13-dependent collagen lattice contraction by fibroblasts: evidence for integrin-coordinated collagen proteolysis

We have previously determined that integrin α11β1 is required on mouse periodontal ligament (PDL) fibroblasts to generate the force needed for incisor eruption. As part of the phenotype of α11(-/-) mice, the incisor PDL (iPDL) is thickened, due to disturbed matrix remodeling. To determine the molecular mechanism behind the disturbed matrix dynamics in the PDL we crossed α11(-/-) mice with the Immortomouse and isolated immortalized iPDL cells. Microarray analysis of iPDL cells cultured inside a 3D collagen gel demonstrated downregulated expression of a number of genes in α11-deficient iPDL cells, including matrix metalloproteinase-13 (MMP-13) and cathepsin K. α11(-/-) iPDL cells in vitro displayed disturbed interactions with collagen I during contraction of attached and floating collagen lattices and furthermore displayed reduced MMP-13 protein expression levels. The MMP-13 specific inhibitor WAY 170523 and the Cathepsin K Inhibitor II both blocked part of the α11 integrin-mediated collagen remodeling. In summary, our data demonstrate that in iPDL fibroblasts the mechanical strain generated by α11β1 integrin regulates molecules involved in collagen matrix dynamics. The positive regulation of α11β1-dependent matrix remodeling, involving MMP-13 and cathepsin K, might also occur in other types of fibroblasts and be an important regulatory mechanism for coordinated extracellular and intracellular collagen turnover in tissue homeostasis.

Expression of MMP-8 and MMP-13 in the development of periradicular lesions

AIM

To elucidate the expressions of MMP-8 and MMP-13 in experimentally induced rat periradicular lesions by means of the reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemical staining.

METHODOLOGY

Thirty rats were used and periradicular lesions in mandibular first molar teeth were established following pulp exposure. The animals were sacrificed at 0 (no exposure control), 1, 2, 3, 4 and 6 weeks after pulp exposure. The right molars were used for RT-PCR analysis of MMP-8 and MMP-13. The left molars were subjected to immunohistochemical staining with both MMPs. The areas of these lesions were measured histometrically, and the numbers of both reactive cells in the periapical portion were counted per unit area. Significant differences were analysed by the Mann-Whitney U-test.

RESULTS

MMP-8 gene expression gradually increased from 2 to 4 weeks, but slightly decreased at 6 weeks. MMP-13 gene expression gradually increased from 1 to 3 weeks. At 4 and 6 weeks, the level of expression was as high as that at 3 weeks. Immunohistochemically, MMP-8 was first detected at 2 weeks and gradually increased until 4 weeks. MMP-13 gradually increased from 1 to 4 weeks. Both MMPs decreased at 6 weeks. The area of the periradicular lesions gradually increased from 1 to 4 weeks, showing a large increase in week 2 and 3 in particular, but then decreased in week 6. MMP-13-expressing cells were significantly greater than MMP-8-positive cells at week 1 and 2.

CONCLUSIONS

These findings indicate that MMP-8 and MMP-13 were related to the development of periradicular lesions. It is suggested that MMP-13 increased from an early stage during their development and that MMP-8 is involved in the progression of tissue destruction including bone resorption.

Temporal and spatial expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases following myocardial infarction

Following a myocardial infarction (MI), the homeostatic balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) is disrupted as part of the left ventricle (LV) response to injury. The full complement of responses to MI has been termed LV remodeling and includes changes in LV size, shape and function. The following events encompass the LV response to MI: (1) inflammation and LV wall thinning and dilation, (2) infarct expansion and necrotic myocyte resorption, (3) accumulation of fibroblasts and scar formation, and (4) endothelial cell activation and neovascularization. In this review, we will summarize MMP and TIMP roles during these events, focusing on the spatiotemporal localization and MMP and TIMP effects on cellular and tissue-level responses. We will review MMP and TIMP structure and function, and discuss specific MMP roles during both the acute and chronic phases post-MI, which may provide insight into novel therapeutic targets to limit adverse remodeling in the MI setting.

Expression patterns of collagen types I and III in the capsule of a rat knee contracture model

Our objective was to determine the changes in expression of collagen types I and III in the capsule of a rat knee contracture model. The unilateral knee joints of adult male rats were rigidly immobilized at 150 degrees of flexion using a rigid plastic plate and screws for 3 days, 1, 2, 4, 8, and 16 weeks (immobilized group). Sham-operated animals had holes drilled in the femur and tibia with screws inserted without a plate (control group). The expression patterns of collagen types I and III in the anterior and posterior capsule were evaluated by in situ hybridization (ISH), quantitative real-time polymerase chain reaction (qPCR), immunohistochemistry (IHC), and Western blotting (WB). Expressions of collagen types I and III were decreased after immobilization compared to the control group by ISH and qPCR. The expression was not changed after immobilization compared to the control group by IHC and WB. The expression of mRNA and protein levels of collagen types I and III were not increased after immobilization, which indicated that accumulation of the two types of collagen was not the etiology of joint contracture. Another process, such as capsule and synovial adhesions, may be one possible cause of joint contracture.

Decreased collagen and increased matrix metalloproteinase-13 in experimental abdominal aortic aneurysms in males compared with females

BACKGROUND

This study examined differences in sex in collagen regulation during rodent experimental abdominal aortic aneurysm formation.

METHODS

Infrarenal aortas of male and female rats were perfused with elastase or saline (control). Aortic diameters were measured at baseline (day 0) and on postoperative days 7 and 14. Transforming growth factor-beta 1, collagen subtypes I and III, and matrix metalloproteinase-13 (MMP-13; collagenase-3) expression and/or protein levels from aortic tissue were determined by real-time reverse transcription polymerase chain reaction and Western blotting. Aortic tissue was stained for total collagen, neutrophils, and macrophages using immunohistochemistry on days 4 and 7.

RESULTS

At 7 and 14 days after perfusion, aortic diameter increased in elastase-perfused males compared with females (P < .001 for each). At 4 and 7 days postperfusion, significantly more neutrophils and macrophages were present in elastase-perfused males compared with females. By 7 days postperfusion, protein levels of transforming growth factor-beta 1 were less in males compared with females (P = .04). Type I collagen levels also decreased on days 7 (P < .001) and 14 (P = .002), and type III collagen levels decreased on days 7 (P < .001) and 14 (P < .001) in males compared with females. With Masson's trichrome stain, less adventitial collagen was observed in the elastase-perfused males compared with females. MMP-13 expression (P < .001) and protein levels (P = .006) in elastase-perfused males were greater than females on day 14.

CONCLUSION

This study documents a decrease in types I and III collagen with a concurrent increase in MMP-13 after elastase perfusion in males compared with females. These data suggest that alterations in extracellular matrix collagen turnover may be responsible for altered abdominal aortic aneurysm formation between sexes.

Immunohistochemical and biochemical assay of versican in human sound predentine/dentine matrix

Aim of this study was to investigate the distribution of versican proteoglycan within the human dentine organic matrix by means of a correlative immunohistochemical analysis with field emission in-lens scanning electron microscope (FEI-SEM), transmission electron microscope (TEM), fluorescence microscope (FM) and biochemical assay. Specimens containing dentine and predentine were obtained from non carious human teeth and divided in three groups: 1) FEI-SEM group: sections were exposed to a pre-embedding immunohistochemical procedure; 2) TEM group: specimens were fixed, demineralised, embedded and submitted to a post-embedding immunohistochemical procedure; 3) FM group: sections mineralised and submitted to a pre-embedding immunohistochemical procedure with fluorescence labelling. Specimens were exposed to two different antibodies to assay distribution of versican fragments and whole versican molecule. Western Blotting analysis of dentine and pulp extracts was also performed. The correlative FEI-SEM,TEM and FM analysis revealed positive immunoreaction for versican fragments both in predentine and dentine, while few gold particles identifying the whole versican molecule were found in predentine only under TEM. No labelling of versican whole molecule was detected by FEI-SEM and FM analysis. The immunoblotting analysis confirmed the morphological findings. This study suggests that in fully developed human teeth versican fragments are significant constituents of the human dentine and predentine organic matrix, while versican whole molecule can be visualised in scarce amount within predentine only. The role of versican fragments within human dentine organic matrix should be further elucidated.

Matrix metalloproteinase 2 activity decreases in human periodontal ligament fibroblast cultures submitted to simulated orthodontic force

Orthodontic force compresses the periodontal ligament promoting the expression of pro-inflammatory mediators and matrix metalloproteinases responsible for tooth movement. The extent in time while periodontal cells are being treated and the increment in the amount of mechanical stress caused by the orthodontic force is thought to regulate the levels of metalloproteinases in the periodontal tissue. To study the possible regulation in the activity of metalloproteinases 2, 3, 7, 9, and 10 by simulated orthodontic force, human periodontal ligament fibroblast cultures were centrifuged (141 × g) for 30, 60, 90, and 120 min, simulating the orthodontic force. Cell viability, protein quantification, and activity of metalloproteinases by zymography were evaluated at 24, 48, and 72 h after centrifugation in both cell lysates and growth medium. The activity of the 72-kDa matrix metalloproteinase 2 was decreased at 24 h regardless of the duration of centrifugation and at 48 h in cells centrifuged for 30 min only. Decrease in the amount of total protein in lysates was seen at 48 and 72 h with no change in cell viability. The data seem to indicate that the amount of mechanical stress regulates the levels of secreted matrix metalloproteinase 2. In addition, the centrifugation as a model for simulated orthodontic force may be used as a simple and reliable method to study the role played by matrix metalloproteinases in periodontal ligament when submitted to mechanical force as occurring during tooth movement.

Comparative study of gene expression during tooth eruption and orthodontic tooth movement in mice

OBJECTIVE

The aim of this study was to understand tooth eruption by comparing the gene expression during tooth eruption and orthodontic tooth movement (OTM).

MATERIALS AND METHODS

Orthodontic force was applied on maxillary molars for 2, 4, 7 and 14 days to study tooth movement. Mice at PN 0, 7, 10, 15 and 21 were fixed to observe tooth eruption. Comparative study of two procedures was assessed by haematoxylin and eosin, tartrate-resistant acid phosphatase staining and in situ hybridization for matrix metalloproteinase (Mmp)2, 13, bone sialoprotein (Bsp) and osteocalcin (Ocn).

RESULTS

Tartrate-resistant acid phosphatase activity and expression of Mmp2, 13 were obviously detectable in the compression region during OTM. They were also identified in the occlusal and apical region of alveolar bone during tooth eruption. Strong expression of Bsp and Ocn was detectable at the tension side during OTM. These genes were also expressed in the inner lateral region of alveolar bone adjacent to the tooth, but absent in the inner surface of the occlusal and root apical regions during tooth eruption.

CONCLUSION

The process of alveolar bone metabolism during developmental eruption and OTM shares the same mechanism. Internal force, as the orthodontic force for OTM, may be initiating factor for tooth eruption.

Downregulation of matrix metalloproteinases in hyperplastic dental follicles results in abnormal tooth eruption

In this study, we compared the gene expression profiles of non-syndromic hyperplastic dental follicle (HDF) fibroblasts and normal dental follicle (NDF) fibroblasts using cDNA microarrays, quantitative PCR, and immunohistochemical staining. Microarray analysis showed that several collagens genes were upregulated in the HDFos, including collagen types I, IV, VIII, and XI and TIMP-1, -3, and -4 (fold ratio > 2.0). In contrast, the expression of MMP-1, -3, -10, and -16 together with IL-8 was more than two fold downregulated. The differential expression of the genes encoding alkaline phosphatase, MMP-1, -3, -8, and IL-8 was confirmed by quantitative RT-PCR, while that of 24 HDFs and 18 NDFs was confirmed by immunohistochemical analysis. However, HDFs showed stronger expression of MMP-3 than NDFs (P < 0.001). Collectively, these results indicate that defective regulation of MMPs mediating connective tissue remodeling may be responsible for abnormal tooth eruption.

Three genes control the timing, the site and the size of blastema formation in Drosophila

Regeneration is a vital process to maintain and repair tissues. Despite the importance of regeneration, the genes responsible for regenerative growth remain largely unknown. In Drosophila, imaginal disc regeneration can be induced either by fragmentation and in vivo culture or in situ by ubiquitous expression of wingless (wg/wnt1). Imaginal discs, like appendages in lower vertebrates, initiate regeneration by wound healing and proliferation at the wound site, forming a regeneration blastema. Most blastema cells maintain their disc-specific identity during regeneration; a few cells however, exhibit stem-cell like properties and switch to a different fate, in a phenomenon known as transdetermination. We identified three genes, regeneration (rgn), augmenter of liver regeneration (alr) and Matrix metalloproteinase-1 (Mmp1) expressed specifically in blastema cells during disc regeneration. Mutations in these genes affect both fragmentation- and wg-induced regeneration by either delaying, reducing or positioning the regeneration blastema. In addition to the modifications of blastema homeostasis, mutations in the three genes alter the rate of regeneration-induced transdetermination. We propose that these genes function in regenerative proliferation, growth and regulate cellular plasticity.

MMP-13 (collagenase 3) immunolocalisation during initial orthodontic tooth movement in rats

Matrix metalloproteinases (MMPs) are enzymes that play a central role in periodontal ligament (PDL) space remodelling during orthodontic tooth movement. It has previously been shown that messenger RNA levels of MMP-13 increase significantly following the application of orthodontic forces. The aim of the present study was to examine immunolocalisation of MMP-13 and to evaluate if this collagenase is time-dependently and differentially detected within the PDL following the application of orthodontic forces to create areas of compression and tension. This was achieved by placing elastic bands between the maxillary first and second molars of 16 male Sprague-Dawley rats (each weighing 120-200g) for 12 and 24h. The molar-bearing segments were dissected and processed for histological and immunohistochemical examination. Binding of a monoclonal antibody was used to evaluate MMP-13 localization using an indirect streptavidin/biotin immunperoxidase technique. MMP-13 was found to be inducible at the protein level by the application of forces. The PDL and osteoblast-lineage cells showed a time-dependent increase in immunolabelling of MMP-13. Immunolabelling of MMP-13 was detected initially on the compression side, and then on both the compression and the tension sides. Since this increase in MMP-13 immunolabelling occurred very early following the application of an orthodontic force in both PDL and alveolar bone, this would indicate that MMP-13 might play an important role during tooth movement.

Up-regulation of matrix metalloproteinase-8 by betel quid extract and arecoline and its role in 2D motility

Betel quid (BQ) and matrix metalloproteinase-8 (MMP-8) play roles in oral diseases. Here, we analyzed the regulation of MMP-8 by BQ and its effect on cell migration. We found that BQ extract (BQE) increased the secretion of an 85kDa caseinolytic proteinase, specifically precipitated by an anti-MMP-8 antibody, in the culture medium of OECM-1, an oral squamous cell carcinoma (OSCC) cell line. BQE also stimulated MMP-8 secretion in an esophageal carcinoma cell line, CE81T/VGH, in a dose-dependent manner, and MMP-8 protein was maximally expressed at 24h after BQE treatment in OECM-1. The BQE-induced MMP-8 expression was dose-dependently inhibited by PD98059. Arecoline, the major alkaloid of areca nut, was tested to dose-dependently up-regulate MMP-8 protein level. Moreover, both arecoline- (4.7-fold) and BQE-selected (5.5-fold) CE81T/VGH cells expressed higher MMP-8 protein level and exhibited enhanced two-dimensional (2D) motility (p=0.009 in both cells) than parental cells. The enhanced motility of arecoline- (p=0.006) and BQE-selected (p=0.002) cells was both specifically blocked by an anti-MMP-8 antibody. We conclude that BQ may accelerate tumor migration by stimulating MMP-8 expression through MEK pathway in at least some carcinomas of the upper aerodigestive tract. Furthermore, arecoline may be one of the positive MMP-8 regulators among BQ ingredients.

Advances in defining regulators of cementum development and periodontal regeneration

Substantial advancements have been made in defining the cells and molecular signals that guide tooth crown morphogenesis and development. As a result, very encouraging progress has been made in regenerating crown tissues by using dental stem cells and recombining epithelial and mesenchymal tissues of specific developmental ages. To date, attempts to regenerate a complete tooth, including the critical periodontal tissues of the tooth root, have not been successful. This may be in part due to a lesser degree of understanding of the events leading to the initiation and development of root and periodontal tissues. Controversies still exist regarding the formation of periodontal tissues, including the origins and contributions of cells, the cues that direct root development, and the potential of these factors to direct regeneration of periodontal tissues when they are lost to disease. In recent years, great strides have been made in beginning to identify and characterize factors contributing to formation of the root and surrounding tissues, that is, cementum, periodontal ligament, and alveolar bone. This review focuses on the most exciting and important developments over the last 5 years toward defining the regulators of tooth root and periodontal tissue development, with special focus on cementogenesis and the potential for applying this knowledge toward developing regenerative therapies. Cells, genes, and proteins regulating root development are reviewed in a question-answer format in order to highlight areas of progress as well as areas of remaining uncertainty that warrant further study.

Aryl hydrocarbon receptor activation impairs extracellular matrix remodeling during zebra fish fin regeneration

Adult zebra fish completely regenerate their caudal (tail) fin following partial amputation. Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) inhibits this regenerative process. Proper regulation of transcription, innervation, vascularization, and extracellular matrix (ECM) composition is essential for complete fin regeneration. Previous microarray studies suggest that genes involved in ECM regulation are misexpressed following activation of the aryl hydrocarbon receptor. To investigate whether TCDD blocks regeneration by impairing ECM remodeling, male zebra fish were i.p. injected with 50 ng/g TCDD or vehicle, and caudal fins were amputated. By 3 days postamputation (dpa), the vascular network in the regenerating fin of TCDD-exposed fish was disorganized compared to vehicle-exposed animals. Furthermore, immunohistochemical staining revealed that axonal outgrowth was impacted by TCDD as early as 3 dpa. Histological analysis demonstrated that TCDD exposure leads to an accumulation of collagen at the end of the fin ray just distal to the amputation site by 3 dpa. Mature lepidotrichial-forming cells (fin ray-forming cells) were not observed in the fins of TCDD-treated fish. The capacity to metabolize ECM was also altered by TCDD exposure. Quantitative real-time PCR studies revealed that the aryl hydrocarbon pathway is active and that matrix-remodeling genes are expressed in the regenerate following TCDD exposure.

The MMP activity in developing rat molar roots and incisors demonstrated by in situ zymography

Matrix metalloproteinases (MMPs) have been expressed during root development and periodontal tissue formation, whereas it is not known if these MMP molecules are enzymatically active to degrade the extracellular matrices (ECMs). The present study was designed to investigate the gelatinolytic and collagenolytic activity in rat molar root and incisor development. Three-week old rat mandibles were frozen and cut without fixation or decalcification and processed for in situ zymography using substrates gelatin and collagen. The enzymatic activity was assessed according to the intensity of fluorescence due to the lysis of the substrates. Odontoblasts, predentin, cementum, bone and the enamel matrix showed the high activity. The present study demonstrated MMP activity in calcified tissues using in situ zymography for the first time and the possible involvement of the MMP activity in molar root and incisor development and periodontal tissue formation.

Periostin is an extracellular matrix protein required for eruption of incisors in mice

A characteristic tooth of rodents, the incisor continuously grows throughout life by the constant formation of dentin and enamel. Continuous eruption of the incisor is accompanied with formation of shear zone, in which the periodontal ligament is remodeled. Although the shear zone plays a role in the remodeling, its molecular biological aspect is barely understood. Here, we show that periostin is essential for formation of the shear zone. Periostin-/- mice showed an eruption disturbance of incisors. Histological observation revealed that deletion of periostin led to disappearance of the shear zone. Electron microscopy revealed that the disappearance of the shear zone resulted from a failure in digestion of collagen fibers in the periostin-/- mice. Furthermore, immunohistochemical analysis using anti-periostin antibodies demonstrated the restricted localization of periostin protein in the shear zone. Periostin is an extracellular matrix protein, and immunoelectron microscopy showed a close association of periostin with collagen fibrils in vivo. These results suggest that periostin functions in the remodeling of collagen matrix in the shear zone.

Expression of Versican and ADAMTS During Rat Tooth Eruption

A disintegrin and metalloprotease with thrombospondin type 1 motifs (ADAMTS) is a family of extracellular proteases and implicated in cleaving proteoglycans, such as aggrecan, versican and brevican. No information is available about expression or localization of these ADAMTSs in teeth. Versican is a large chondroitin sulfate proteoglycan that is present in a variety of connective tissue including dental pulp, dentin, cementum and periodontal ligaments. The present study was designed to investigate expression of ADAMTSs and versican during rat tooth eruption. Rat maxillary first molars in weeks 1, 2, 3, 4 and 6 were examined. The mRNA expression of ADAMTS1, ADAMTS4, ADAMTS5 and versican was localized using in situ hybridization. ADAMTS1, ADAMTS4, ADAMTS5 and versican were expressed in dental pulp cells, odontoblasts, cementoblasts, cementocytes, periodontal ligament cells, osteoblasts and osteocytes. The temporal and spatial expression pattern in these cellular phenotypes was comparable among ADAMTSs and versican. The present study suggests that dental pulp cells, odontoblasts, cementoblasts, cementocytes, periodontal ligament cells, osteoblasts and osteocytes may be involved in both production and degradation of versican with secreting ADAMTS1, ADAMTS4 and ADAMTS5.

Matrix metalloproteinases (MMPs) safeguard osteoblasts from apoptosis during transdifferentiation into osteocytes: MT1-MMP maintains osteocyte viability

Osteoblasts undergo apoptosis or differentiate into either osteocytes or bone-lining cells after termination of bone matrix synthesis. In this study, we investigated the role of matrix metalloproteinases (MMPs) in differentiation of osteoblasts, bone formation, transdifferentiation into osteocytes, and osteocyte apoptosis. This was accomplished by using calvarial sections from the MT1-MMP-deficient mouse and by culture of the mouse osteoblast cell line MC3T3-E1 and primary mouse calvarial osteoblasts. We found that a synthetic matrix metalloprotease inhibitor, GM6001, strongly inhibited bone formation in vitro of both primary osteoblasts and MC3T3 cells by approximately 75%. To further investigate at which level of osteoblast differentiation MMP inhibition was attenuating osteoblast function, we found that neither preosteoblast nor mature osteoblast activity was affected. In contrast, cell survival of osteoblasts forced to transdifferentiate into osteocytes in 3D type I collagen gels were inhibited by more than 50% when exposed to 10 microM GM6001 and to Tissue Inhibitor of Metalloproteinase-2 (TIMP-2), a natural MT1-MMP inhibitor. This shows the importance of MMPs in safeguarding osteoblasts from apoptosis when transdifferentiating into osteocytes. By examination of osteoblasts and osteocytes embedded in calvarial bone in the MT1-MMP deficient mice, we found that MT1-MMP deficient mice had 10-fold higher levels of apoptotic osteocytes than wild-type controls. We have previously shown that MT1-MMP activates latent Transforming Growth Factorbeta (TGF-beta). These findings strongly suggest that MT1-MMP-activated TGF-beta maintains osteoblast survival during transdifferentiation into osteocytes, and maintains mature osteocyte viability. Thus, the interrelationship of MMPs and TGF-beta may play an important role in bone formation and maintenance.

mRNA expression and protein localization of dentin matrix protein 1 during dental root formation

Dentin matrix protein 1 (DMP1) is an acidic phosphoprotein. DMP1 was initially detected in dentin and later in other mineralized tissues including cementum and bone, but the DMP1 expression pattern in tooth is still controversial. To determine the precise localization of DMP1 messenger RNA (mRNA) and the protein in the tooth, we performed in situ hybridization and immunohistochemical analyses using rat molars and incisors during various stages of root formation. During root dentin formation of molars, DMP1 mRNA was detected in root odontoblasts in parallel with mineralization of the dentin. However, the level of DMP1 mRNA expression in root odontoblasts decreased near the coronal part and was absent in coronal odontoblasts. DMP1 protein was localized along dentinal tubules and their branches in mineralized root dentin, and the distribution of DMP1 shifted from the end of dentinal tubules to the base of the tubules as dentin formation progressed. During the formation of the acellular cementum, DMP1 mRNA was detected in cementoblasts lining the acellular cementum where its protein was localized. During the formation of the cellular cementum, DMP1 mRNA was detected in cementocytes embedded in the cellular cementum but not in cementoblasts, and its protein was localized in the pericellular cementum of cementocytes including their processes. During dentin formation of incisors, DMP1 mRNA was detected in odontoblasts on the cementum-related dentin, where its protein was localized along dentinal tubules near the mineralization front. The localization of DMP1 mRNA and protein in dentin and cementum was related to their mineralization, suggesting that one of the functions of DMP1 may be involved in the mineralization of dentin and cementum during root formation.

Levels and molecular forms of MMP-7 (matrilysin-1) and MMP-8 (collagenase-2) in diseased human peri-implant sulcular fluid

OBJECTIVES

Matrix metalloproteinases (MMPs) play crucial role in various tissue destructive inflammatory processes by degrading almost all peri-cellular and basement membrane components. MMP-8 (collagenase-2) is the major MMP in periodontitis. MMP-7 (matrilysin-1), in addition to its ability to degrade matrix and basement membrane components, activates other latent pro-MMPs and defensins, host cell-derived antimicrobial cryptidins. The aim of the present study was to characterize the relationship, levels and molecular forms of MMP-8 and MMP-7 in diseased peri-implant sulcular fluid (PISF).

MATERIALS AND METHODS

Seventy-two human dental implant fluid samples were collected with filter paper strips from peri-implant sulci from healthy and untreated diseased implant sites. Gingival index (GI) and/or bone resorption (BR) were also recorded. Western immunoblot method with polyclonal anti-human-MMP-8 and monoclonal anti-human-MMP-7 antibodies was used, and immunoreactivities were quantified with computer scanning program. The effects of MMP inhibitors (doxycycline, chemically modified tetracycline-3, clodronate, CTT-peptide and marimastat) were studied on the activity of recombinant human matrilysin-1 (MMP-7) using beta-casein degradation assay.

RESULTS

The levels of active forms of MMP-8 and MMP-7 were significantly elevated in diseased PISF in relation to healthy PISF. Furthermore, MMP-8 and MMP-7 levels correlated significantly to each other and GI. MMP-8 was present not only as bands corresponding to 75-kDa polymorphonuclear leukocyte (PMN) -type pro- and 65-kDa active forms, but also as 55-kDa non-PMN-type pro- and 45-kDa active forms. Immunoreactivities > 80 kDa most likely represented dimeric and/or inhibitor-bound MMP-8 complexes and the low molecular weight (< 30 kDa) species were apparently degraded fragments. In diseased PISF, 19-21-kDa active MMP-7 and 28-30-kDa pro-MMP-7 species were detected, and the active 19-21-kDa forms of MMP-7 predominated in diseased PISF. Doxycycline (50 micro m and 250 micro m), chemically modified non-antimicrobial tetracycline (CMT-3) (50 micro m and 100 micro m), clodronate (a bisphosphonate, 20 micro m and 500 micro m) and the cyclic CTT (CTTHWGFTLC)-peptide (125 micro m and 250 micro m), all known broad-spectrum or selective MMP-inhibitors, did not inhibit the activity of human recombinant MMP-7; only marimastat (1 micro m and 5 micro m) inhibited MMP-7.

DISCUSSION

Increased immunoreactivities of the active MMP-8 and MMP-7 species in PISF from diseased peri-implantitis lesions eventually reflect the stage and course of peri-implantitis; MMP-7 may potentially act as MMP-8 and defensin activator in diseased PISF.

CONCLUSION

The elevated levels of MMP-8 and matrilysin-1/MMP-7 were identified in active forms in diseased PISF, but MMP-7 was less prominent. MMP inhibitors, potential future tissue protective drugs, seemingly do not interfere with the defensive antibacterial action of MMP-7.

Expression of MMP-8 and MMP-13 genes in the periodontal ligament during tooth movement in rats

Periodontal ligament tissue is remodeled on both the tension and compression sides of moving teeth during orthodontic tooth movement. The present study was designed to clarify the hypothesis that the expression of MMP-8 and MMP-13 mRNA is promoted during the remodeling of periodontal ligament tissue in orthodontic tooth movement. We used the in situ hybridization method and semi-quantitative reverse-transcription/polymerase chain-reaction analysis to elucidate the gene expression of MMP-8 and MMP-13 mRNA. Expression of MMP-8 and MMP-13 mRNA transiently increased on both the compression and tension sides during active tooth movement in vivo. The gene expression of MMP-8 and MMP-13 was induced by tension, while compression indirectly promoted the gene expression of MMP-8 and MMP-13 through soluble factors in vitro. Thus, we concluded that the expression of MMP-8 and MMP-13 is differentially regulated by tension and compression, and plays an important role in the remodeling of the periodontal ligament.