Collagen fibers and inflammatory cells in healthy and diseased human gingival tissues: a comparative and quantitative study by immunohistochemistry and automated image analysis

Viscoelastic behavior of oral mucosa. A rheological study using small-amplitude oscillatory shear tests

The purpose of this work was to determine the viscoelastic behavior of porcine and human oral mucosa under physiological conditions of temperature, hydration and chewing. The linear elastic and viscous shear moduli of these soft tissues were determined by small-amplitude oscillatory shear (SAOS) tests at masticatory frequency using a stress-controlled rheometer equipped with an immersion cell on punched biopsies 8 mm in diameter. Non physiological conditions of temperature were also used to access other parameters such as the denaturation temperature of collagen. First, the different parameters such as normal force, frequency and maximal strain were adjusted to obtain reliable data on porcine mucosa. The optimal normal force was 0.1N and the linear viscoelastic limit was found for a strain amplitude of 0.5% for both 0.1 and 1 Hz. The storage moduli of porcine mucosa, ranging from 5 to 16 kPa, were in the same range as cutaneous tissues determined by SAOS at equivalent frequencies. The storage modulus, superior to the loss modulus G″, indicates a predominant elastic contribution to shear stress in chewing conditions. Second, this protocol evidenced an influence of the anatomic site of the mouth on the viscoelastic behavior of porcine mucosa, mandibular biopsies having higher storage moduli than maxillary biopsies. Temperature scans showed the mechanical manifestation of collagen denaturation in the 60-70 °C range as previous calorimetric analyses. Finally, this mechanical protocol was successfully adapted to characterize human mucosa in an elderly population. It was shown that the elastic modulus is impacted by local inflammation (gingivitis), decreasing significantly from 6 ± 1.4 kPa to 2.5 ± 0.3 kPa.

Reduction in Gingival Bleeding after Atelocollagen Injection in Patients with Hashimoto's Disease-A Pilot Study

Periodontal diseases are one of the main causes of tooth loss and the second most common oral disease after carries. Patients with autoimmune diseases, such as Hashimoto's disease, are more often vulnerable to infection. In the study group of patients, despite the lack of other signs of gingivitis, bleeding occurred after tooth brushing or minor trauma. Bleeding on probing is the first objective sign of ongoing inflammation. The study was conducted on a group of 17 patients diagnosed with Hashimoto's disease. The atelocollagen Linerase (100 mg) thinned with 5 mL 0.9% NaCl was used. A total of 0.05 mL of solution was injected into keratinized gingiva, two millimeters above the gingival papillae basement, four times in two-week intervals. The greatest decrease in the number of bleeding points was observed after the first and second injections of atelocollagen. After the third and fourth injections, the average BOP continued to decrease, but the decline was very slow. The use of atelocollagen made it possible to eliminate bleeding symptoms in the study group.

Automated scoring of total inflammation in renal allograft biopsies

BACKGROUND

Computer-assisted scoring is gaining prominence in the evaluation of renal histology; however, much of the focus has been on identifying larger objects such as glomeruli. Total inflammation impacts graft outcome, and its quantification requires tools to identify objects at the cellular level or smaller. The goal of the current study was to use CD45 stained slides coupled with image analysis tools to quantify the amount of non-glomerular inflammation within the cortex.

METHODS

Sixty renal transplant whole slide images were used for digital image analysis. Multiple thresholding methods using pixel intensity and object size were used to identify inflammation in the cortex. Additionally, convolutional neural networks were used to separate glomeruli from other objects in the cortex. This combined measure of inflammation was then correlated with rescored Banff total inflammation classification and outcomes.

RESULTS

Identification of glomeruli on biopsies had high fidelity (mean pixelwise dice coefficient of .858). Continuous total inflammation scores correlated well with Banff rescoring (maximum Pearson correlation .824). A separate set of thresholds resulted in a significant correlation with alloimmune graft loss.

CONCLUSIONS

Automated scoring of inflammation showed a high correlation with Banff scoring. Digital image analysis provides a powerful tool for analysis of renal pathology, not only because it is reproducible and can be automated, but also because it provides much more granular data for studies.

Stiffness of tongue squamous cell carcinoma measured using strain elastography correlates with the amount of collagen fibers in the tumor

OBJECTIVES

To evaluate the stiffness of tongue squamous cell carcinoma (TSCC) using ultrasound strain elastography, a relatively new sonographic imaging technique, and to identify the factors that affect this stiffness.

METHODS

We treated 62 patients diagnosed with muscle invasive TSCC, who were treated at the department of oral surgery of our institution. Each patient's tumor stiffness was semi-quantified according to the ratio of cancer to tongue muscle strain measured using ultrasound strain elastography (the strain ratio). Histopathological diagnosis was made on the same section as the ultrasound strain elastography. We set the following histopathological parameters: cancer cell content in the tumor area (%CCC), collagen fiber content in the tumor area (%CFC), and tumor-infiltrating inflammatory cell content in the stromal compartment (%TIIC). Spearman's rank correlation (rs) was used to assess correlations, and P values < 0.05 were considered significant.

RESULTS

The mean strain ratio was 9.7 ± 9.8. The mean %CCC was 38.4 ± 11.3%, and % CFC was 31.1 ± 7.8%, % TIICs was 19.9 ± 8.9%. Log (strain ratio) by ultrasound strain elastography was positively correlated with %CFC (r_s = 0.379, P = 0.024). %CFC was negatively correlated with %TIICs (r_s =  - 0.318, P = 0.012). No correlations were observed between other clinico-histopathological factors and either strain ratio, or %CFC.

CONCLUSION

The strain ratio of the cancer to the strain of the tongue muscle measured through ultrasound strain elastography positively correlates with the collagen fiber content of the tumor area.

Colony-stimulating factor-1 receptor blockade attenuates inflammation in inflamed gingival tissue explants

BACKGROUND AND OBJECTIVE

Colony-stimulating factor-1 receptor (CSF-1R) regulates myeloid cell function and mediates osteoclastogenesis. CSF-1R blockade has been suggested as a potential therapeutic target to halt inflammation and bone resorption; however, the expression and function of CSF-1R in human gingiva is yet unknown.

METHODS

Gingival tissue was collected from 22 non-periodontitis controls and 31 periodontitis (PD) patients. CSF-1R expression in gingival tissue was assessed with q-PCR, western blot, and immunohistochemistry (IHC). Cell surface expression of CSF-1R was analyzed by flow cytometry. The effects of CSF-1R inhibition on the production of inflammatory mediators by inflamed gingival tissue explants and peripheral blood mononuclear cells (PBMCs) were assessed with a bead-based multiplex array and ELISA.

RESULTS

CSF-1R protein expression was increased in gingival tissue from PD patients compared with controls as assessed with western blot (1.5-fold increase) and IHC (4.5-fold increase). Similar proportions of HLA-DR⁺ CD64⁺ cells and comparable CSF-1R expression in this cell population were found in gingival tissue from PD patients and controls. In peripheral blood monocytes, CSF-1R was predominantly expressed by non-classical and intermediate monocytes. Targeting CSF-1R in gingival tissue explants attenuated the production of MMP-1, MMP-2, MMP-12, and MMP-13. The blocking in PBMCs attenuated the production of IL-8 and MMP-9.

CONCLUSION

These results indicate that CSF-1R is elevated in PD, and its inhibition attenuates inflammatory mediators in the inflamed gingival tissue and circulating myeloid cells. Together these findings suggest that CSF-1R might be involved in regulating inflammatory processes in PD, and a potential therapeutic target to reduce the harmful inflammation.

Analysis of collagen fibers in human gingival tissues using picrosirius red stain under polarized microscope

Background:

Collagen fibers are the main element of gingival connective tissue and contribute a leading role in the preservation of structural integrity and tissue function. Hence, its degradation is regarded as the main marker of periodontal disease progression.

Aim:

The aim of this study is to analyze and compare collagen fibers, their birefringence pattern in healthy and in diseased gingival tissues stained using picrosirius red stain (PRS) and the polarizing microscope.

Materials and Methods:

A total of 90 participants screened were divided into the control group (healthy gingiva) and experimental group (moderate periodontitis and severe periodontitis) based on the clinical parameters. Gingival tissue sections were stained with PRS and observed under the polarized microscope to assess the type of collagen fibers in healthy and diseased gingival tissue. Statistical analysis was performed using the one-way ANOVA and Tukey multiple comparison test.

Results:

The healthy group revealed well-packed collagen in a parallel pattern with a strong birefringence, whereas in severe periodontitis group showed loosely packed collagen fibers in a haphazard pattern suggestive of severe destruction of the extracellular matrix. The moderate periodontitis group had a blended mixture of thick and thin fibers.

Conclusions:

Collagen fibers showed birefringence property when stained with PRS that helps in a better understanding of normal and pathological conditions.

Mechanisms Regulating Muscle Regeneration: Insights into the Interrelated and Time-Dependent Phases of Tissue Healing

Despite a massive body of knowledge which has been produced related to the mechanisms guiding muscle regeneration, great interest still moves the scientific community toward the study of different aspects of skeletal muscle homeostasis, plasticity, and regeneration. Indeed, the lack of effective therapies for several physiopathologic conditions suggests that a comprehensive knowledge of the different aspects of cellular behavior and molecular pathways, regulating each regenerative stage, has to be still devised. Hence, it is important to perform even more focused studies, taking the advantage of robust markers, reliable techniques, and reproducible protocols. Here, we provide an overview about the general aspects of muscle regeneration and discuss the different approaches to study the interrelated and time-dependent phases of muscle healing.

Histological and inflammatory analysis to diagnostic method of proximal gingivitis by flossing

OBJECTIVES

The aim of this study was to assess with histological and inflammatory analysis the use of flossing as a diagnostic method for detecting proximal gingivitis.

MATERIAL AND METHODS

This is a diagnostic accuracy paper composed of two different studies. In the first study, three groups were identified based on papilla status: bleeding (+) with both methods (N = 26); bleeding (+) with dental floss, but no bleeding (-) with probing (N = 26); and no bleeding (-) with either method (N = 26). One papilla from all 78 participants was biopsied and analyzed for the determination of inflammatory infiltrate and percentage of collagen fibers. Sensibility, specificity, positive and negative predictive, and accuracy values were analyzed. In the second study, the volume of gingival crevicular fluid (GCF) was analyzed in 49 participants with flossing+/probing- and flossing-/probing- at contralateral proximal sites. The GCF volume was compared between these sites (n = 172).

RESULTS

Significantly greater frequencies of moderate/intense inflammation were found in the flossing+/probing+ (100%) and flossing+/probing- (92.3%) groups compared to those in the flossing-/probing- (0%) group. Significantly different percentages of collagen fibers were found among the three groups (flossing+/probing+ (40.90 ± 3.68); flossing+/probing- (45.78 ± 4.55); flossing-/probing- (60.01 ± 36.66)) (P < 0.001). Dental floss increased the balance between sensitivity and specificity values and showed highest positive predictive (100%) and accuracy (97%) values. Among the 172 sites evaluated, positive bleeding sites had a significantly greater volume of GCF (38 (27-68)) than negative sites (25 (16-51)) (P < 0.001).

CONCLUSIONS

The findings suggest that flossing can be used as a diagnostic method for proximal gingivitis in subjects with no history of periodontitis.

CLINICAL RELEVANCE

Dental floss can be used as a complementary diagnostic method for proximal gingivitis in adults without clinical attachment loss in clinical practice as well as epidemiology studies.

Revisiting the Page & Schroeder model: the good, the bad and the unknowns in the periodontal host response 40 years later

In their classic 1976 paper, Page & Schroeder described the histopathologic events and the types of myeloid cells and lymphocytes involved in the initiation and progression of inflammatory periodontal disease. The staging of periodontal disease pathogenesis as 'initial', 'early', 'established' and 'advanced' lesions productively guided subsequent research in the field and remains fundamentally valid. However, major advances regarding the cellular and molecular mechanisms underlying the induction, regulation and effector functions of immune and inflammatory responses necessitate a reassessment of their work and its integration with emerging new concepts. We now know that each type of leukocyte is actually represented by functionally distinct subsets with different, or even conflicting, roles in immunity and inflammation. Unexpectedly, neutrophils, traditionally regarded as merely antimicrobial effectors in acute conditions and protagonists of the 'initial' lesion, are currently appreciated for their functional versatility and critical roles in chronic inflammation. Moreover, an entirely new field of study, osteoimmunology, has emerged and sheds light on the impact of immunoinflammatory events on the skeletal system. These developments and the molecular dissection of crosstalk interactions between innate and adaptive leukocytes, as well as between the immune system and local homeostatic mechanisms, offer a more nuanced understanding of the host response in periodontitis, with profound implications for treatment. At the same time, deeper insights have generated new questions, many of which remain unanswered. In this review, 40 years after Page & Schroeder proposed their model, we summarize enduring and emerging advances in periodontal disease pathogenesis.

Complex Intratissue Microbiota Forms Biofilms in Periodontal Lesions

Periodontitis is caused by dysbiotic subgingival bacterial communities that may lead to increased bacterial invasion into gingival tissues. Although shifts in community structures associated with transition from health to periodontitis have been well characterized, the nature of bacteria present within the gingival tissue of periodontal lesions is not known. To characterize microbiota within tissues of periodontal lesions and compare them with plaque microbiota, gingival tissues and subgingival plaques were obtained from 7 patients with chronic periodontitis. A sequencing analysis of the 16S rRNA gene revealed that species richness and diversity were not significantly different between the 2 groups. However, intersubject variability of intratissue communities was smaller than that of plaque communities. In addition, when compared with the plaque communities, intratissue communities were characterized by decreased abundance of Firmicutes and increased abundance of Fusobacteria and Chloroflexi. In particular, Fusobacterium nucleatum and Porphyromonas gingivalis were highly enriched within the tissue, composing 15% to 40% of the total bacteria. Furthermore, biofilms, as visualized by alcian blue staining and atomic force microscopy, were observed within the tissue where the degradation of connective tissue fibers was prominent. In conclusion, very complex bacterial communities exist in the form of biofilms within the gingival tissue of periodontal lesions, which potentially serve as a reservoir for persistent infection. This novel finding may prompt new research on therapeutic strategies to treat periodontitis.

Extracellular ATP is a key modulator of alveolar bone loss in periodontitis

Periodontal diseases are initiated by pathogenic bacterial biofilm activity that induces a host inflammatory cells immune response, degradation of dento gingival fibrous tissue and its detachment from root cementum. It is well accepted, that osteoclastic alveolar bone loss is governed exclusively through secretion of proinflammatory cytokines. Nevertheless, our findings suggest that once degradation of collagen fibers by MMPs occurs, a drop of cellular strains cause immediate release of ATP from marginal gingival fibroblasts, cell deformation and influx of Ca+2. Increased extracellular ATP (eATP) by interacting with P2×7 purinoreceptors, present on fibroblasts and osteoblasts, induces generation of receptor activator of nuclear factor kB ligand (RANKL) that further activates osteoclastic alveolar bone resorption and bone loss. In addition, increased eATP levels may amplify inflammation by promoting leukocyte recruitment and NALP3-inflammasome activation via P2×7. Then, the inflammatory cells secrete cytokines, interleukin IL-1, TNF and RANKL that further trigger alveolar bone resorption. Moreover, eATP can be secreted from periodontal bacteria that may further contribute to inflammation and bone loss in periodontitis. It seems therefore, that eATP is a key modulator that initiates the pathway of alveolar bone resorption and bone loss in patients with periodontal disease. In conclusion, we propose that strain release in gingival fibroblasts aligned on collagen fibers, due to activity of MMP, activates release of ATP that triggers the pathway of alveolar bone resorption in periodontitis. We predict that by controlling the eATP interaction with its cellular purinoreceptors will reduce significantly bone loss in periodontitis.

Antimicrobial photodynamic therapy with photosensitizer in ethanol improves oxidative status and gingival collagen in a short-term in periodontitis

BACKGROUND

This study evaluated the antimicrobial photodynamic therapy (aPDT) effects using the methylene blue (MB) in ethanol 20% on systemic oxidative status and collagen content from gingiva of rats with periodontitis.

METHODS

Rats were divided into five experimental groups: NC (negative control; no periodontitis); PC (positive control; periodontitis without any treatment); SRP (periodontitis and scaling and root planing), aPDT I (periodontitis and SRP+aPDT+MB solubilized in water), and aPDT II (periodontitis and SRP+aPDT+MB solubilized in ethanol 20%). After 7days of removal of the ligature, the periodontal treatments were performed. At 7/15/30days, gingival tissue was removed for morphometric analysis. The erythrocytes were used to evaluate systemic oxidative status.

RESULTS

PC group showed higher lipoperoxidation levels at 7/15/30days. aPDT indicated a protective influence in erythrocytes at 15days observed by the elevation in levels of systemic antioxidant defense. aPDT II group was the only one that restored the total collagen area in 15days, and recovered the type I collagen area at the same time point.

CONCLUSIONS

aPDT as an adjunct to the SRP can induce the systemic protective response against oxidative stress periodontitis-induced and recover the gingival collagen, thus promoting the healing periodontal, particularly when the MB is dissolved in ethanol 20%.

Picrosirius red staining: a useful tool to appraise collagen networks in normal and pathological tissues

Specific staining of the extracellular matrix components is especially helpful in studying tissue remodeling, particularly in the case of connective tissue pathologies. As developed by Junqueira and colleagues in 1979, specific staining by Picrosirius red is one of the most important stains to study collagen networks in different tissues. Under polarized light, collagen bundles appear green, red or yellow, and are easily differentiated from the black background, thus allowing for quantitative morphometric analysis. As Junqueira and colleagues point out, many studies use color staining to differentiate collagen bundles and to specify collagen types, yet other studies report that polarized colors only reflect fiber thickness and packing. Using a simple histological example, our study illustrates the inability of Picrosirius red staining to differentiate collagen types, since the absorbed amount of polarized light by this dye strictly depends on the orientation of the collagen bundles.

Histopathologic and histomorphometric studies and determination of IL-8 in patients with periodontal disease

BACKGROUND

Periodontitis is an inflammatory disease characterized by connective tissue breakdown and alveolar bone resorption.

OBJECTIVE

The aim of this study was to make a quantitative evaluation of the gingival tissue components in biopsies from patients with different clinical states of periodontal disease and to determine the relationship between the presence of interleukin-8 and the tissue destruction.

MATERIALS AND METHODS

The study group consisted of 33 biopsies from adult subjects. A total of 25 periodontal patients were sub-classified on the basis of the clinical and radiographic criteria in mild, moderate and advanced periodontitis. Gingival samples were obtained from patients in the course of basic periodontal surgeries as a muco-periostic collate. Data were analyzed by the SPSS system.

RESULTS

Collagen fibres decreased as non-specific chronic states increased. A lymphocyte inflammatory infiltrate changed to a lymphoplasmocytary form. Reactivity to interleukin-8 was detected with the severity of the histopathologic diagnoses; however there was no association with the clinical diagnoses.

CONCLUSIONS

Histopathology and histomorphometry of gingival tissue changed with the degree of inflammation. No evidence of interleukin-8 as a biomarker for clinical diagnoses of periodontitis was obtained.

Evaluation of peri-implant mucosa: clinical, histopathological and immunological aspects

OBJECTIVE

The aim was to compare the inflammatory response in peri-implant mucosa between patients with peri-implantitis (PP-group) and patients with healthy peri-implant tissues (HP-group).

MATERIALS AND METHODS

Two fragments of peri-implant mucosa of 18 patients were collected and serial sections were performed for histological and immunohistochemical analysis.

RESULTS

When compared with HP-group, PP-group showed higher immunostained cell density for TGF-β, IL-17 and CD31, beyond greater density of red cells, leukocytes, mast cells chymase (MCC) and mast cell tryptase (MCT). HP-group patients showed higher IL-13 expression and increased amount of collagen fibres when compared with PP-group. In PP-group there was significant positive correlation between MCT density and density of blood vessels immunostained, and between MCC density and density of blood vessels immunostained. There was significant negative correlation between the IL-17 density and collagen percentage.

CONCLUSIONS

This study demonstrated that in patients with peri-implantitis there was higher of TGF-β and IL-17, indicating that these cytokines are directly involved in the inflammatory process. Thus, understanding the influence of cytokines in the peri-implantitis installation, new therapies could be developed in order to inhibit the synthesis of IL-17 and induce synthesis of IL-13 in peri-implant tissue, contributing to increase the longevity of the implant.

The relationship between matrix metalloproteinases (MMP-3, -8, -9) in serum and peripheral lymphocytes (CD8+ , CD56+ ) in Down syndrome children with gingivitis

BACKGROUND AND OBJECTIVE

Altered immune response may be a major contributor to periodontal disease in Down syndrome. This study investigated the relationship between peripheral lymphocytes and matrix metalloproteinases (MMPs) in serum in Down syndrome children with gingivitis.

MATERIAL AND METHODS

Children with Down syndrome (n = 10) and healthy controls (n = 10) were clinically and radiographically examined during dental treatment under general anaesthesia. Peripheral blood and gingival crevicular fluid were collected from each subject and concentrations were determined: serum MMP-2, -3, -8 and -9; serum tissue inhibitors of metalloproteinases (TIMP) -1, -2 and -3; and gingival crevicular fluid. Leukocytes were isolated from peripheral blood and the relative amounts (%) of the various cell phenotypes were analysed using flow cytometry. In addition, peripheral blood cells were treated with Porphyromonas gingivalis lipopolysaccharide and levels of MMPs and TIMPs measured.

RESULTS

Concentrations of MMP-3, MMP-8 and TIMP-1 in serum were significantly higher (p < 0.05) in the Down syndrome group compared to the controls. When peripheral blood leukocytes were cultured in the presence or absence of P. gingivalis lipopolysaccharide, MMP-8 levels were significantly (p < 0.05) higher in the Down syndrome group compared to controls. Children with Down syndrome exhibited significant positive correlations between CD8(+) T cells and MMP-8 (r = 0.630; p = 0.050), between CD8(+) T cells and MMP-9 (r = 0.648; p = 0.043), and between CD56(+) NK cells and MMP-3 (r = 0.828; p = 0.003) compared to controls.

CONCLUSIONS

The positive relationship of serum MMP-3, -8 and -9 with immune cells in children with Down syndrome may facilitate migration of CD8(+) T cells and CD56(+) NK cells into the periodontal tissue, which may contribute to the increased degradation of periodontal tissue in individuals with Down syndrome.

TLR2 signaling and Th2 responses drive Tannerella forsythia-induced periodontal bone loss

Periodontal disease (PD) is a chronic inflammation of the tooth-supporting soft tissue and alveolar bone due to infection by a select group of gram-negative microbes, which leads to tooth loss if untreated. Because mice deficient in CD4(+) cells are resistant to infection-induced alveolar bone loss, Th cells have been implicated in bone-destructive processes during PD. However, the extent to which different Th cell subtypes play roles in pathogenesis or host protection remains to be defined and is likely to vary depending on the dominant microorganism involved. By far, Porphyromonas gingivalis is the best-studied periodontal microbe in PD. Although the gram-negative anaerobe Tannerella forsythia is also a vital contributor to periodontal bone loss, almost nothing is known about immune responses to this organism. Previous studies from our laboratory revealed that T. forsythia induces periodontal bone loss in mice and that this bone loss depends on the bacterially expressed BspA protein. In this study, we showed that T. forsythia activates murine APCs primarily through TLR2-dependent signaling via BspA. Furthermore, T. forsythia infection causes a pronounced Th2 bias, evidenced by T cell expression of IL-5, but not IFN-γ or IL-17, in draining lymph nodes. Consistently, deficiencies in TLR2 or STAT6 result in resistance to T. forsythia-induced alveolar bone loss. Thus, TLR2 signaling and Th2 cells play pathogenic roles in T. forsythia-induced alveolar bone destruction.

Expression of prostaglandin E synthases in periodontitis immunolocalization and cellular regulation

The inflammatory mediator prostaglandin E(2) (PGE(2)) is implicated in the pathogenesis of chronic inflammatory diseases including periodontitis; it is synthesized by cyclooxygenases (COX) and the prostaglandin E synthases mPGES-1, mPGES-2, and cPGES. The distribution of PGES in gingival tissue of patients with periodontitis and the contribution of these enzymes to inflammation-induced PGE(2) synthesis in different cell types was investigated. In gingival biopsies, positive staining for PGES was observed in fibroblasts and endothelial, smooth muscle, epithelial, and immune cells. To further explore the contribution of PGES to inflammation-induced PGE(2) production, in vitro cell culture experiments were performed using fibroblasts and endothelial, smooth muscle, and mast cells. All cell types expressed PGES and COX-2, resulting in basal levels of PGE(2) synthesis. In response to tumor necrosis factor (TNF-α), IL-1β, and cocultured lymphocytes, however, mPGES-1 and COX-2 protein expression increased in fibroblasts and smooth muscle cells, accompanied by increased PGE(2), whereas mPGES-2 and cPGES were unaffected. In endothelial cells, TNF-α increased PGE(2) production only via COX-2 expression, whereas in mast cells the cytokines did not affect PGE(2) enzyme expression or PGE(2) production. Furthermore, PGE(2) production was diminished in gingival fibroblasts derived from mPGES-1 knockout mice, compared with wild-type fibroblasts. These results suggest that fibroblasts and smooth muscle cells are important sources of mPGES-1, which may contribute to increased PGE(2) production in the inflammatory condition periodontitis.

Spectral region optimization for Raman-based optical biopsy of inflammatory lesions

OBJECTIVE

The biochemical alterations between inflammatory fibrous hyperplasia (IFH) and normal tissues of buccal mucosa were probed by using the FT-Raman spectroscopy technique. The aim was to find the minimal set of Raman bands that would furnish the best discrimination.

BACKGROUND

Raman-based optical biopsy is a widely recognized potential technique for noninvasive real-time diagnosis. However, few studies had been devoted to the discrimination of very common subtle or early pathologic states as inflammatory processes that are always present on, for example, cancer lesion borders.

METHODS

Seventy spectra of IFH from 14 patients were compared with 30 spectra of normal tissues from six patients. The statistical analysis was performed with principal components analysis and soft independent modeling class analogy cross-validated, leave-one-out methods.

RESULTS

Bands close to 574, 1,100, 1,250 to 1,350, and 1,500 cm(-1) (mainly amino acids and collagen bands) showed the main intragroup variations that are due to the acanthosis process in the IFH epithelium. The 1,200 (C-C aromatic/DNA), 1,350 (CH(2) bending/collagen 1), and 1,730 cm(-1) (collagen III) regions presented the main intergroup variations. This finding was interpreted as originating in an extracellular matrix-degeneration process occurring in the inflammatory tissues. The statistical analysis results indicated that the best discrimination capability (sensitivity of 95% and specificity of 100%) was found by using the 530-580 cm(-1) spectral region.

CONCLUSIONS

The existence of this narrow spectral window enabling normal and inflammatory diagnosis also had useful implications for an in vivo dispersive Raman setup for clinical applications.

Impact of photodynamic therapy on inflammatory cells during human chronic periodontitis

The aim of this study was to evaluate the effects of the photodynamic therapy (PDT) on the inflammatory infiltrate and on the collagen network organization in human advanced chronic periodontitis. Two different drug delivery systems (DDS) were tested (liposomes and nanoemulsions) to determine if the effects of PDT could differ according to the DDS used. Sixteen patients presenting two teeth with chronic advanced periodontitis and important tooth mobility with clinical indication of extraction were included in the group liposomes (group L, n=8) or in the group nanoemulsions (group N, n=8) in order to compare the effects of each DDS. Seven days before extractions one tooth of each patient was treated with PDT using phthalocyanine derivatives as photosensitizers and the contralateral tooth was taken as control. In group L the density of gingival collagen fibers (66±19%) was significantly increased (p<0.02) when compared to controls (35±21%). Concerning the antigen-presenting cells, PDT had differential effects depending on the drug delivery system; the number of macrophages was significantly decreased (p<0.05) in group L while the number of Langerhans cells was significantly decreased in group N (p<0.02). These findings demonstrate that PDT presents an impact on gingival inflammatory phenomenon during chronic periodontitis and leads to a specific decrease of antigen-presenting cells populations according to the drug delivery system used.

T1 relaxation time and magnetic resonance imaging of inflamed gingival tissue

OBJECTIVES

The aim of this study was to evaluate the use of MRI as a non-invasive method for the characterization of the inflammation and healing processes in periodontal tissues.

METHODS

For the in vitro study, 99 gingival samples were collected during periodontal surgical treatment and T1 relaxation time measurements were performed and correlated to the probing depth measurements recorded at the collection sites. For the in vivo study, a group of eight patients with moderate to advanced periodontal disease was examined with pre-contrast and Gd-DTPA contrast-enhanced T1 weighted MRI both before and 3 months after non-surgical periodontal therapy. On the MR images of the 8 patients, 53 regions of interest (ROIs) were selected. For each ROI, the ratio between post- and pre-contrast signal intensity (RSI) was calculated and used as a measure for the degree of inflammation.

RESULTS

The in vitro T1 relaxation times measurements of gingival samples showed an increase in relaxation times with the increase of probing depth at the sites of tissue removal. The in vivo studies demonstrated that the reduction of inflammation and probing depth in gingival tissues after non-surgical periodontal therapy correlates with a decrease of RSI in T1 weighted MR images. The non-invasively obtained data provide the characteristic ratio U, which shows that two distinct types of inflammation occurred in the examined group of patients.

CONCLUSIONS

The results of MRI provide a new possibility to characterize the type and healing process of periodontal inflammation.

The influence of type I diabetes mellitus on the expression and activity of gelatinases (matrix metalloproteinases-2 and -9) in induced periodontal disease

BACKGROUND AND OBJECTIVE

Periodontal disease corresponds to a group of lesions that affect the tooth-supporting tissues present in the dental follicle. Although bacterial plaque is important, the immune response also contributes to the destruction of periodontal tissues. Diabetes mellitus is closely associated with the development, progression and severity of periodontal disease because it not only affects extracellular matrix organization but also the tissue response to inflammation. The objective of the present investigation was to study the influence of diabetes on experimental periodontal disease by evaluating the degradation of extracellular matrix through the analysis of matrix metalloproteinase (MMP)-2 and MMP-9 expression and activity, using immunofluorescence, zymography and real-time reverse transcription-polymerase chain reaction.

MATERIAL AND METHODS

Wistar rats were divided into normal and diabetic groups and evaluated 0, 15 and 30 d after the induction of periodontal disease by ligature.

RESULTS

MMP-2 and -9 were detected in epithelial cells, in the blood vessel endothelium and in connective tissue cells. The same profile of enzymatic expression of MMP-2 and -9 was observed in normal and diabetic animals, with a peak in activity at day 15 of inflammation. However, in diabetic animals, MMP-2 gelatinolytic activity was reduced after the inflammatory stimulus, whereas that of MMP-9 was increased. MMP-2 gene expression decreased with inflammation in both normal groups and groups with diabetes. In contrast, MMP-9 expression increased in normal animals and decreased in diabetic animals after inflammation.

CONCLUSION

The results suggest the involvement of MMP-2 and -9 in the dynamics of periodontal disease and that variation in their expression levels results in differences in tissue organization and wound healing in normal and diabetic animals.

Clinical and histomorphometric characteristics of three different families with hereditary gingival fibromatosis

OBJECTIVE

To examine the histomorphologic and histomorphometric features of tissue from 3 unrelated families with hereditary gingival fibromatosis (HGF).

STUDY DESIGN

Twelve affected individuals from 3 HGF families and 3 control subjects were evaluated. Gingival samples were fixed in formalin and embedded in paraffin for hematoxylin and eosin stain to count the number of fibroblast and inflammatory cells. Sirius red staining was performed to quantitate the amount of collagen present.

RESULTS

Histomorphologic analysis of HGF showed extension of epithelial rete ridges into the underlying lamina propria and the presence of collagen bundles in the connective tissue. Analysis of the mean area fraction of collagen showed that there were significant increases in the collagen fraction for all HGF types compared with control subjects (P < .05). There were significant increases in the number of fibroblasts for HGFa and HGFb compared with control subjects (P < .05). The number of fibroblasts for HGFc were similar to that for control subjects.

CONCLUSIONS

The collagen fraction was significantly greater in all HGF types compared with controls. The number of fibroblasts was significantly increased in 2 of the 3 HGF types compared with controls. These data indicate that different mechanisms may be responsible for tissue enlargement in different forms of HGF.

Characterization of fibroblasts with Son of Sevenless-1 mutation

Although non-syndromic hereditary gingival fibromatosis (HGF) is genetically heterogeneous, etiologic mutations have been identified only in the Son of Sevenless-1 gene (SOS1). To test evidence of increased cell proliferation, we studied histological, morphological, and proliferation characteristics in monolayer and three-dimensional cultures of fibroblasts with the SOS1 g.126,142-126,143insC mutation. Histological assessment of HGF gingiva indicated increased numbers of fibroblasts (30%) and increased collagen (10%). Cell proliferation studies demonstrated increased growth rates and 5-bromo-2-deoxyuridine incorporation for HGF fibroblasts. Flow cytometry showed greater proportions of HGF fibroblasts in the G2/M phase. Attachment of HGF fibroblasts to different extracellular matrix surfaces demonstrated increased formation of protrusions with lamellipodia. HGF fibroblasts in three-dimensional culture showed greater cell proliferation, higher cell density, and alteration of surrounding collagen matrix. These findings revealed that increased fibroblast numbers and collagen matrix changes are associated with mutation of the SOS1 gene in vitro and in vivo.

Topical Application of Drugs Influencing Cytoskeleton and Cell Contractility Affects Alveolar Bone Loss in Rats

BACKGROUND

Several studies have shown that sectioning bundles of collagen fibers in the marginal gingiva during surgical procedures in animals is a distinct stimulus for alveolar bone resorption. Normally, gingival and periodontal fibroblasts, which reside on these collagen fibers, create physiological traction forces generated by the cytoskeleton. By splitting the fibers, traction forces are released, inducing changes in the cytoskeleton and cell shape. In this study, four drugs were selected, including cytochalasin D, EDTA, sodium orthovanadate, and H-7, all influencing the cytoskeleton-integrin-extracellular matrix (ECM) pathway, for their ability to reduce alveolar bone loss by local application.

METHODS

The drugs were applied locally only once at the site of mucoperiosteal flap surgery in a rat model. Cytochalasin D (1 microl/microl), EDTA (0.24 mg/microl), sodium orthovanadate (0.02 mg/microl), and H-7 (0.10 microl/microl), each separately, were carried by a protective paste and placed immediately after elevating the flap. The analysis of alveolar bone loss was performed 3 weeks after surgery by scanning the microradiographic films of the mandible cross-sections. The percentages of cross sections with no, moderate, or severe bone loss in treated in comparison to non-treated rats are presented.

RESULTS

EDTA, sodium orthovanadate, and H-7 were significantly effective in reducing alveolar bone loss. They were effective in reducing the amount of severe bone loss by 53%, 20%, and 58% while increasing the number of sections with no bone loss by 25%, 23%, and 35%, respectively. Cytochalasin D reduced alveolar bone loss insignificantly.

CONCLUSION

EDTA, sodium orthovanadate, and H-7 are effective in reducing alveolar bone loss in rats following mucoperiosteum surgery.

Human Skin and Gingival Keratinocytes Show Differential Regulation of Matrix Metalloproteinases When Combined With Fibroblasts in 3-Dimensional Cultures

BACKGROUND

Matrix metalloproteinases (MMP) and their inhibitors are expressed in tissues during interactions between keratinocytes and fibroblasts. Maintaining the balance between MMPs and their inhibitors is critical; failure to do so can lead to severe tissue damage or complete destruction, as seen in periodontal disease. Previously we showed that 3-dimensional (3-D) cultures of homotypically-combined skin and gingival cells mimicked the tissues in protein and lipid production, but heterotypic cultures did not.

METHODS

We examined the production and activation of MMPs in these homotypic and heterotypic combinations of skin and gingival keratinocytes and fibroblasts during the critical time that they reformed the tissues. Primary fibroblasts and keratinocytes were isolated from normal human gingiva and skin and grown in 3-D cultures for up to 42 days. MMP-1, MMP-2, and MMP-9 in the media and inhibition of MMPs from these cultures were analyzed.

RESULTS

These experiments determined that skin fibroblasts grown with skin or gingival keratinocytes secrete increased amounts of MMP-1 compared to gingival fibroblasts; that the interaction of keratinocytes with fibroblasts decreases the amount of MMP-2 produced by the fibroblasts in 3-D cultures; that skin keratinocytes, but not gingival keratinocytes, interact with fibroblasts to upregulate expression of the active form of MMP-9; and that medium conditioned by gingival 3-D cultures does not contain an inhibitor of MMP-9.

CONCLUSION

Varying the type of fibroblast beneath the keratinocytes allowed us to determine that skin and gingival keratinocytes differentially regulate the production and activation of MMP-9, but not MMP-2, a finding that could influence the success of tissue grafting after periodontal surgery.

Histomorphometric study of the healing of human oral mucosa after gingivoplasty and low-level laser therapy

BACKGROUND AND OBJECTIVES

The aim of the present study was to analyze the effects of diode laser irradiation on the healing of human oral mucosa.

MATERIALS AND METHODS

After gingivoplasty, the right hemi-arch (test group) of 16 patients was irradiated with a diode laser. The left side (control group) was not irradiated. Incisional biopsies were performed on both sides at 7, 14, 21, and 60 days after surgery and morphometrically analyzed by light microscopy.

RESULTS

Epithelium width ranged from 260.6 to 393.5 microm. Volume densities of basal (20.2%), prickle cell (55.6%), and cornified (24.2%) layers remained stable. The peak number of neutrophils were 6 cells/mm(2) and the mononuclear cells were 44 cells/mm(2). Collagen fibers (80%) and fibroblasts (14%) occupied the main volume of connective tissue. The one-way ANOVA and the paired Student's t-test were used for statistical analysis (P < 0.05).

CONCLUSION

Low-level laser therapy did not accelerate the healing of oral mucosa after gingivoplasty.

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

This study examined the effects of a vegetable extract from Lupinus albus (LU105) on MMPs and TIMPs secreted by human gingival fibroblasts in culture. LU105 was extracted from seeds of L. albus and is freely soluble in water. Gelatin zymography showed that control human gingival fibroblasts maintained in culture for 48 h express pro-MMP2 (progelatinase A) in the culture medium while the active form of MMP2 (gelatinase A), the active form of MMP9 (gelatinase B), and pro-MMP9 (progelatinase B) are not detected. Fibroblasts derived from inflamed gingiva expressed in the culture medium increased amounts of pro-MMP2 (progelatinase A) compared with controls and significant amounts of pro-MMP9 (progelatinase B). LU105 diminished the expression by gingival fibroblasts derived from inflamed tissue of both pro-MMP2 and pro-MMP9. Furthermore LU105 did not modify the amount of TIMP2 expressed in culture by controls or by gingival fibroblasts derived from inflamed tissue. TIMP1 and MMP1 significantly decreased when LU105 was added in the culture media of gingival fibroblasts derived from inflamed tissue compared with control fibroblasts. Thus LU105 seems to offer an opportunity to restore a correct balance between MMP2, MMP9, MMP1, and their natural inhibitors, i.e., TIMP1 and TIMP2 in human inflamed gingiva.

Combined local application of tetracycline and bisphosphonate reduces alveolar bone resorption in rats

BACKGROUND

Recent animal studies have shown that a combination of chemically-modified tetracyclines together with bisphosphonates, when delivered systemically, are synergistically effective in suppressing periodontal bone loss. In the present study, we explored the combined efficacy of local delivery of alendronate and tetracyclines in reducing alveolar bone loss.

METHODS

Eighty-six (86) male Wistar rats were used in these experiments. The flap was elevated using a special periosteal elevator, on both sides of the mandible, as described previously. A gelfoam pellet containing the drugs was applied between the alveolar bone and the mucoperiosteal flap, according to the experimental protocol. The rats were divided into 5 treatment groups: 1) alendronate; 2) doxycycline hyclate 10% (DOXY); 3) tetracycline hydrochloride 1% (TET); 4) alendronate + DOXY; and 5) alendronate + TET. In the operated control sites (C), saline was applied. The rats were sacrificed 21 days following the flap procedure. Sections of the mandibles (1.5 mm), in a buccal-lingual direction, underwent microradiography and were analyzed for bone loss.

RESULTS

DOXY alone was most effective in reducing bone loss. Alendronate was also effective in reducing bone loss as shown in previous reports. TET did not reduce bone loss significantly when used alone. In combination with alendronate TET was synergistically effective. The combined local treatment of alendronate + DOXY showed no additive effect.

CONCLUSIONS

In the present study, we found that tetracyclines can be most effective in reducing alveolar bone loss when applied locally. The combined local treatment of alendronate and tetracycline may have a synergistic effect.

Expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in healthy and diseased human gingiva

BACKGROUND

The purpose of this study was to quantify the amount of matrix metalloproteinases such as MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, and MMP-13 and tissue inhibitors of metalloproteinases TIMP-1 and TIMP-2 expressed by human gingival explants in culture media and the area fraction (AA%) of gingival collagen fibers according to the degree of inflammation, to investigate a possible correlation between these enzymes and collagen loss.

METHODS

Gingival tissue specimens from 6 healthy controls (group 1), 17 patients with mild gingival inflammation (group 2), 10 patients with moderate gingival inflammation (group 3), and 9 patients with severe gingival inflammation (group 4) were placed in organ culture for 3 days. The MMPs and TIMPs in the culture media were quantified using zymography, dot blotting, and Western blotting. Paraffin gingival sections were stained with sirius red F3Ba for visualization of collagen fibers, then the area fraction (AA%) occupied by the gingival fibers was determined by automated image analysis.

RESULTS

The AA% occupied by collagen fibers significantly decreased from group 1 (53%) to group 4 (35%). The decrease in collagen fibers was inversely correlated with the significant increase in MMP-1, MMP-9, and MMP-13 (dot blotting analysis), with the increase of the active form of MMP-2, and with the active form and proform of MMP-9 (zymography analysis).

CONCLUSION

The present study showed that metalloproteinases, particularly MMP-2, MMP-9, MMP-1, and MMP-13, are involved in the gingival extracellular matrix degradation during periodontitis.

A new approach to treat tissue destruction in periodontitis with chemically modified dextran polymers

Periodontitis are diseases of the supportive tissues of the teeth provoked by bacteria and characterized by gingival inflammation and bone destruction. We have developed a new strategy to repair tissues by administrating agents (RGTA) that mimic heparan sulfates by protecting selectively some of the growth factors naturally present within the injured tissue and interfering with inflammation. After periodontitis induction in hamsters, the animals were left untreated or received weekly i.m. injections of RGTA1507 at a dose of 100 microg/kg, 400 microg/kg, 1.5 mg/kg, or 15 mg/kg for 4 wk. RGTA treatment significantly reduced gingival tissue inflammation, thickened the pocket epithelium by increasing cell proliferation, and enhanced collagen accumulation in the gingiva. A marked reduction in bone loss was observed, resulting from depression of osteoclasia and robust stimulation of bone formation at the dose of 1.5 mg/kg. RGTA treatment for 8 wk at this dose reversed macroscopic bone loss, sharply contrasting with the extensive bone destruction in the untreated animals. RGTA treatment decreased gelatinase A (MMP-2) and B (MMP-9) pro-forms in gingival tissues. Our data indicate that a 4 wk treatment dose-dependently attenuated gingival and bone manifestations of the disease, whereas a longer treatment restored alveolar bone close to controls. By modulating and coordinating host responses, RGTA has unique therapeutic properties and is a promising candidate for the treatment of human periodontitis.

Are cytokines linked to collagen breakdown during periodontal disease progression?

BACKGROUND

Evidence of the role of cytokines produced by resident and inflammatory cells during inflammation is well established. The aim of this study was to quantify in healthy and diseased human gingiva the area fraction (AA%) occupied by collagen fibers and the amount of cytokines such as interleukin (IL)-1beta, IL-4, IL-6, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta, and epidermal growth factor (EGF) to investigate a possible correlation between such cytokines, collagen degradation, and the gingival index.

METHODS

Gingival tissue specimens from 6 healthy controls (group 1), 6 patients with mild gingival inflammation (group 2), 6 patients with moderate gingival inflammation (group 3), and 6 patients with severe gingival inflammation (group 4) were cultured for 72 hours, and the cytokines present in the culture media were quantified using an enzyme-linked immunosorbent assay (ELISA). Paraffin gingival sections from the 24 subjects were stained with sirius red F3Ba for visualization of collagen fibers, then the area fraction (AA%) occupied by the gingival fibers was determined by automated image analysis.

RESULTS

The present study revealed significant differences (P < 0.05) between means of AA% in group 1 (53%), group 2 (41%), group 3 (39.5%), and group 4 (35%) for collagen fibers. Compared to controls, there were significant increases of IL-1beta (groups 3 and 4), IL-6, and TNF-alpha (group 3); a significant decrease of IL-4 (groups 2, 3, and 4) and TGF-beta (groups-2 and, 3); and no change of EGF. The collagen AA% was significantly correlated with the amounts of IL-4 and TGF-beta, and significantly inversely correlated with the amounts of IL-1beta for all 3 inflamed groups and IL-6 and TNF-alpha for groups 2 and 3.

CONCLUSION

The present study showed that EGF was not changed in inflamed gingival tissue and that IL-1beta and IL-4 were particularly and intensively correlated with collagen loss. These 2 cytokines could be markers of clinical severity during active periodontitis.

Strain relaxation of fibroblasts in the marginal periodontium is the common trigger for alveolar bone resorption: a novel hypothesis

In summary, the present commentary proposes a hypothesis that alveolar bone remodeling and bone loss in periodontitis, periodontal surgery, and in orthodontic tooth movement is triggered by a common "strain relaxation" signaling pathway of gingival and periodontal fibroblasts. The abrupt splitting, degradation, or relaxation of collagen fibers in the marginal periodontium produces a "strain relaxation" signal in the local fibroblasts which reside on these fibers, activating an ECM-integrin-cytoskeleton pathway. A cascade of cellular reactions which lead to osteoclastic bone resorption starting on the inner aspect (periodontal) of the alveolar bone then persists. A novel therapeutic approach is suggested here by using locally delivered drugs intervening in the cell contractile apparatus.

Expression of N-acetyltransferases in periodontal granulation tissue

Smoking is a major risk of periodontal diseases. At the site of first contact, the gingiva is exposed to aromatic amines and polycyclic hydrocarbons. These are metabolized by the N-acetyltransferases (NAT), leading to local detoxification and/or activation reactions contributing to the risk of periodontal destruction in smokers. The purpose of this study was to detect the expression of N-acetyltransferase isoenzymes NAT1 and NAT2 in periodontal granulation tissue. In 24 specimens obtained from periodontitis patients or control subjects, mRNA encoding for NAT1 and NAT2 was detected by RT-PCR, and proteins were identified by immunohistochemistry. In periodontal granulation tissues, immunoreactivity for NAT1 and NAT2 was detected in infiltrating leukocytes and fibroblasts. In normal gingiva, both enzymes were found in epithelial cells, whereas NAT1 was also detected in endothelial cells. The results suggest that these enzymes may play a role in the defense against xenobiotics and the accelerated progression of periodontal disease in smokers.

Is collagen breakdown during periodontitis linked to inflammatory cells and expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases in human gingival tissue?

BACKGROUND

Evidence of the role of matrix metalloproteinases (MMPs) produced by resident and inflammatory cells in periodontal destruction is now well established. The purpose of this study was to quantify, in healthy and diseased upper gingival connective tissue, the area fraction (AA%) occupied by collagen fibers, the cell number belonging to inflammatory cell subsets, and the amounts of MMPs and TIMPs (tissue inhibitors of MMPs) in order to investigate the possible correlations, if any, between such molecules, collagen loss, and inflammatory cell subsets.

METHODS

Gingival tissue specimens from 6 healthy controls (C) and 6 patients with severe periodontitis (P) were divided into 2 groups. The first group of specimens was frozen and used for the staining of collagen fibers by sirius red F3Ba and for immunohistochemistry with antibodies against CD8, CD4, CD22, CD68, and TIA-1 molecules. The second group was used for organ culture, zymography, Western blotting, and dot blotting. Morphometric and automated image analysis was performed for the evaluation of the area fraction occupied by collagen fibers, the number of inflammatory cell subsets and for enzymatic activities developed by MMPs, and the amounts of TIMPs expressed during periodontal disease.

RESULTS

In group P, the area fraction of collagen fibers (33 +/- 10%) was significantly decreased (P < 0.0002) when compared to group C (60 +/- 7%), and was correlated with the number of all inflammatory cells and amounts of MMPs and TIMPs. In group P, there were significant increases of CD8+, CD22+, CD68+, and TIA-1+ cells, as well as increases in the amounts of MMP-1, MMP-2, MMP-3, MMP-9, and the active form of MMP-9. The active form of MMP-9 and the amount of TIMP-1 were positively correlated with the number of CD22+, CD68+, and TIA-1+ cells.

CONCLUSIONS

The present study showed an imbalance between MMPs and TIMPs associated with the pathologic breakdown of the extracellular matrix during periodontitis. The active form of MMP-9 could be a marker for the clinical severity of periodontal disease.