Localization of plasminogen activators and plasminogen-activator inhibitors in human gingival tissues demonstrated by immunohistochemistry and in situ hybridization

The plasminogen-activating system plays an important part in tissue proteolysis in physiological as well as pathological processes. Plasminogen activators u-PA (urokinase) and t-PA (tissue) as well as the inhibitors PAI-1 and PAI-2 are present in gingival crevicular fluid in concentrations significantly greater than in plasma. This fact, and the finding that the concentrations of t-PA and PAI-2 are higher in areas with gingival inflammation, indicate local production of these components. The present study describes, by means of in situ hybridization and immunohistochemistry, the localization of the plasminogen activators and their inhibitors in gingival tissues from patients undergoing periodontal surgery. t-PA mRNA and t-PA antigen were primarily found in the epithelial tissues, predominantly in the sulcular and junctional regions, although occasionally in the oral epithelium and in blood vessels of the connective tissue. u-PA and u-PA-receptor signals were seen in single cells within the junctional and sulcular epithelia and adjacent to blood vessels close to the junctional epithelium, but rarely in the oral epithelium. Similar to t-PA, the predominant location of PAI-2 mRNA was the gingival epithelia. In the junctional and sulcular epithelia, PAI-2 mRNA was seen throughout the thickness, while in the oral epithelium the strongest signals were seen in stratum granulosum and stratum spinosum. PAI-1 mRNA was invariably found in the connective tissue associated with blood vessels. The present study confirms earlier indications of local production of plasminogen activators and their inhibitors in gingival tissues. In addition, the results demonstrate that t-PA and PAI-2 in these patients are produced predominantly in the epithelial tissues. Furthermore, the presence of t-PA and PAI-2 seems to be most pronounced in the areas likely to be subjected to bacterial assault.     

Disturbances of gingival fibroblast population homeostasis due to experimentally induced inflammation in the Cynomolgus monkey (Macaca fascicularis): potential mechanism of disease progression

We have studied the relationship between perturbations of fibroblast turnover in inflamed gingiva of different severities. To perform detailed spatial analyses of gingival fibroblast progenitor cells, inflammatory cell infiltrates and blood vessels, 3 Cynomolgus monkeys with healthy periodontium and 2 with naturally occurring gingivitis and ligature-induced periodontitis were pulse-labeled with ³H-thymidine. Morphometric analyses of radioautographs from mid-sagittal supra-alveolar gingival connective tissues of incisors were performed in sites subjacent to junctional, sulcular and oral epithelium, in the body of the lamina propria and just superior to the alveolar crest. The percentage of fibroblasts incorporating ³H-thymidine label, expressed as the labeling index (LI), was higher subjacent to the sulcular epithelium in periodontitis (1.73±0.37) than in healthy sites (1.06±0.22). This was not statistically significant (0.05 < p < 0.1) due to the small number of animals used. The sites subjacent to the sulcular epithelium also exhibited the largest increase in lymphocyte density from health to gingivitis (p < 0.01). In contrast, the LI of fibroblasts subjacent to the oral epithelium was 5-fold higher in healthy (0.82±0.17) compared to periodontitis sites (0.13 ± 0.09; p < 0.05). Labeled fibroblasts were found close to blood vessels in all compartments and in all disease states; distance to blood vessels was reduced in inflamed sites (p < 0.10). There were increased numbers of blood vessels per unit area in the lamina propria of gingivitis compared to healthy sites. However, there were no regional differences with respect to blood vessel numbers or area in sites subjacent to junctional epithelium with different disease states. The results indicate that: 1) experimentally-induced inflammation in the gingiva of Cynomolgus monkeys is associated with site-specific perturbations of cell turnover; 2) fibroblast progenitors are preferentially situated adjacent to blood vessels as in the periodontal ligament; 3) the vascular response to inflammation is a generalized increase in blood vessel numbers, but not their size; 4) reactive proliferation of fibroblasts may compensate for cell death in the lamina propria but is not detectable at the site of connective tissue attachment loss subjacent to the junctional epithelium. Failure to maintain the fibroblast progenitor population may be an important component of attachment loss in progressive periodontitis lesions.     

The effect of topical application of dextran on the gingiva of the beagle dog.

Dextrans derived from Leuconostoc mesenteroides were placed on clinically healthy gingiva of Beagle dogs once a day for 21 days. Control gingival tissues received saline. Both healthy controls and dextran-treated tissues were brushed daily. Inflamed control tissues were obtained by allowing plaque to accumulate for 21 days. Tissues receiving daily application of dextran solutions developed chronic gingival inflammation but displayed no clinical signs of gingivitis. Healthy control gingival tissues showed no clinical signs of gingivitis and minor histologic inflammatory changes. Tissues exposed to dental plaque showed the typical clinical and histological inflammatory changes of gingivitis. Thus dextran, a substance similar to the extracellular polysaccharide found in dental plaque, was able to penetrate the sulcular epithelium, enter healthy gingival connective tissue and cause chronic inflammation. This connective tissue inflammation occurred without inducing any of the clinical signs of gingivitis. Therefore, it is concluded that dextran produced one component of the gingivitis response, chronic histologic inflammation, independent of another major component of the disease, clinical inflammation.     

Distribution and organization of lymphatic vessels in the mouse gingiva: An immunohistochemical study with LYVE-1

OBJECTIVE: This study introduced the usefulness of LYVE-1 immunoreactivity for identification of lymphatic vessels in decalcified tissues, and demonstrated the fine distribution and organization of these vessels in mouse gingiva. DESIGN: After confirming the specificity of anti-mouse LYVE-1, frozen sections of mouse decalcified gingiva were immunostained with the antibody. RESULTS: The LYVE-1-positive lymphatic vessels were clearly found in the connective tissue under the gingival epithelium; these vessels appeared to pass through the lamina propria of the gingiva toward the alveolar crest and run along the external surface of the alveolar bone. The lymphatic vessels were sparse and apart from the oral gingival and sulcular epithelia, while they were dense adjacent to the junctional epithelium. CONCLUSIONS: The dense network of the lymphatic vessels adjacent to the junctional epithelium, which is apparently exposed to foreign antigens, may act as an efficient drainage pathway of the excessive interstitial fluid and immune cells, and play an active role in the immune defense of the gingiva. The present study also revealed the absence of lymphatic connection between gingiva and periodontal ligament.     

Human gingival Langerhans cells in health and disease

Epithelial Langerhans cells in samples of healthy and diseased gingival tissue were studied using ATPase histochemistry and the monoclonal antibodies OKT6 and anti HLA-DR. In healthy gingiva Langerhans cells were seen in both oral and sulcular epithelium; they were generally positioned in the basal layers. No Langerhans cells were seen in junctional epithelium. In diseased tissue there was a large increase in the number of Langerhans cells in both oral and sulcular epithelium with many more being situated in the stratum spinosum. There was an increase in the expression of the Class 2 antigen, HLA-DR, and morphological polarization occurred with dendrites preferentially orientated towards the surface. No Langerhans cells were seen in the pocket lining epithelium of periodontally diseased gingiva.     

Histopathology of initial gingivitis in humans

Abstract The present study concerns the inflammatory alterations in the gingival margin during initial gingivitis in 11–13 year old human subjects. At day 0 of the experiment, all participants had clean teeth and healthy gingiva. All active oral hygiene measures were excluded for 4 days. From upper and lower premolars, which were extracted for orthodontic reasons, contralateral gingival biopsies, including the tooth and the adjacent gingiva, were obtained on days 0 and 4. The presence of inflammatory cells in the junctional epithelium and the adjacent connective tissue was determined quantitatively in semi-thin sections. The collagen content of the gingival margin was also determined. From day 0 to day 4 there was only a slight increase in the number of neutrophilic granulocytes in the junctional epithelium and adjacent connective tissue, while a more pronounced increase was found in the number of mononuclear leukocytes. A loss of collagen was noticed in 4 of the subjects, while 2 did not show any changes in collagen content. The inflammatory reaction seen in the present study differs somewhat from that observed in adult humans and adult dogs. The results correspond more to the reaction seen in juvenile dogs.     

Vascular changes during the development of the rat gingiva

Permeability of the dento-gingival vessels was studied during the development of the gingiva in rats. Groups of animals, aged 19 to 150 days, were injected intravenously with colloidal carbon, and the gingival vessels were observed both macroscopically and microscopically. As the tooth cusps emerged into the oral cavity, vessels labelled with carbon were observed in the connective tissue overlying the tooth and, two to four days later, tracer particles were found in the vessels adjacent to the junctional epithelium. The leaking vessels had a linear pattern beneath the dento-gingival junction in young animals, while in adult rats these vessels formed loops. In the interdental papilla, labelled vessels were observed initially only in the gingiva adjacent to the distal of the first molars, and two days later also in the gingiva facing the mesial of the second molars. There was a progressive increase in gingival blood vessels labelled with carbon until the rats were 150 days old. The results indicate that the inflammatory process and the increased vascular permeability in the gingiva are initialed during tooth eruption and show quantitative and morphological modifications during the organization of the sulcular and junctional epithelia.     

Patterns of cytokeratin expression in human gingival epithelia

Specimens of human gingiva were collected from teenage and adult subjects and frozen sections were stained with an extensive panel of monoclonal antibodies with defined specificities for individual cytokeratins. The results indicated different and distinctive patterns of keratin expression by the oral gingival, oral sulcular and the junctional epithelia. It was observed that epithelium with staining characteristics of sulcular epithelium extended over the gingival crest onto the oral surface of the gingiva. Junctional epithelium showed the unusual pattern of co-expression of keratins typical of the stratifying and of the simple epithelial phenotypes. The patterns of gingival keratin expression are compared with those of other mucosal epithelia. The findings are discussed in relation to mechanisms that may determine or influence the junctional epithelial phenotype.     

Effect of experimental neutropenia on initial gingivitis in dogs

Abstract – The role of neutrophilic granulocytes in the loss of gingival collagen has been studied by inducing experimental neutropenia during initial gingivitis in beagle dogs. Neutropenia was induced for 4 d in three animals with normal gingiva by repeated injections of rabbit anti-neutrophil serum. During neutropenia microbial plaque was allowed to form on the teeth. Samples of junctional (crevicular) leukocytes and gingival fluid were taken on days 0 and 4. Block biopsies of buccal gingiva were obtained on day 4. Stained semi- and ultrathin sections were used for histometric and serologic tissue analysis. Gingival fluid flow increased from day 0 to day 4 in all dogs while junctional leukocytes increased in one dog only. Subgingival plaque had formed in most biopsies, and in the junctional epithelium very few neutrophilic granulocytes were present. In the coronal connective tissue subjacent to the junctional epithelium lymphoid cells, structurally abnormal neutrophilic granulocytes and monocytes/macrophages were diffusely scattered. The gingival collagen appeared mainly displaced by the inflammatory cells rather than dissolved. The data suggest that neutrophilic granulocytes may contribute to the loss of gingival collagen during initial gingivitis in dogs. The neutrophils also seem to be of importance for the limitation of subgingival plaque growth along the tooth surface.     

Cyclosporin A-induced gingival overgrowth in the rat: a histological, ultrastructural and histomorphometric evaluation

This investigation was undertaken to further study cyclosporin A (CsA)-induced gingival overgrowth. Thirty mg/kg/d of vehicle or CsA solutions were given orally to 6-wk-old male Sprague-Dawley rats. After 4, 9, 14 and 19 wk 2 control and 2 experimental rats were anaesthetized, tissues fixed by intracardiac perfusion of fixative solution and jaws processed for Epon inclusion. Histological and ultrastructural studies conducted in a gingival portion (free gingiva) revealed the presence of hyalinization areas and of multinucleated cells (MCs) containing collagen fibrils (connective tissue), of amorphous areas and disorders of keratinization (epithelia). Histomorphometric evaluation indicated that in the CsA rats the mean cross-sectional area of the free gingiva was 2.52-fold increased compared to the controls. The connective tissue comprised 41.43% of this area (instead of 31.49% in controls). Additional histomorphometric evaluation was performed in 3 groups of free gingival portions: control (C group), CsA-non-respondent (CsA-nR) and CsA-respondent (CsA-R). The cross-sectional gingival areas studied were slightly lower than the mean area of all the control sites previously defined (groups C and CsA-nR) or showed the higher degrees of enlargement (CsA-R). In the CsA-R group the mean cross-sectioned area of the vessel profiles was increased and the number of fibroblast profiles decreased. In the CsA-nR group the number of vessel profiles and that of MCs profiles were increased. In the epithelia of the CsA-R group were increased (a) keratinized epithelia: thickness; thickness of the inner and of the outer compartments; surface area of spinous cell profiles; (b) oral gingival epithelium: number of cell layers (inner compartment); (c) oral sulcular epithelium: surface area of granular cell profiles; (d) junctional epithelium: thickness; number of cell layers. These results indicate that (a) the CsA induced modifications are not limited to enlarged gingiva (b) the overgrowth of the GCT is the result of a vasodilatation and of an increase in the volume of the extracellular matrix and (c) the increase of the epithelial thickness is mainly the result of a cell hypertrophy in the keratinized epithelia and of a cell hyperplasia in the junctional epithelium.     

Initial gingivitis in dogs

The gingival characteristics after four days of gingivitis development have been studied in three Beagle dogs. Gingival normality was induced by regular tooth cleaning and gingivitis was provoked by abolishing oral hygiene procedures and giving the animals a soft diet. Measurements of the gingival fluid flow and the amount of crevicular leukocytes served to clinically assess the gingival condition. Semi- and ultra-thin sections from contralateral biopsies of buccal gingival tissues from premolars obtained on day 0 and day 4 respectively were subjected to stereologic analysis based on morphometric point counting procedures. On day 0 of the experiment two dogs revealed minute amounts of gingival fluid and crevicular leukocytes and the gingival tissues of these dogs were normal. The third dog had somewhat higher amounts of the gingival parameters and the connective tissue adjacent to the junctional epithelium harboured a small lymphoid infiltrate occupying 8.3 ± 2.8% of the gingival tissues. On day 4 the gingival fluid flow and the amounts of crevicular leukocytes were increased in all dogs compared to their values on day 0. The coronal con nective tissue in the two dogs with initially normal gingiva revealed on day 4 an infiltrated portion which occupied 6.1 ± 2.4% of the gingival tissues. The infiltrate was predominated by neutrophilic granulocytes, monocytes, macrophages, immunoblasts and small lymphocytes. A 60% loss of the collagen density in the infiltrated fraction was noted between biopsies from day 0 and day 4 in these two dogs. The tissues of the dog which entered the experiment with a preestablished lymphoid infiltrate reacted with similar but more intense inflammatory processes on day 4 than those of the dogs with normal gingiva on day 0. The results indicate that initial gingivitis in dogs is characterized by acute exudative inflammation and immunopathological processes as well as by a marked loss of collagen fibers in the connective tissue located beneath the coronal part of the junctional epithelium. Possible mechanisms responsible for the observed alterations have been discussed.     

Patterns of cytokeratin expression in the epithelia of inflamed human gingiva and periodontal pockets

Fourteen specimens of periodontal pockets and the associated marginal gingiva were collected and either frozen for examination using antibodies against various defined cytokeratin specificities or processed for 2-dimensional gel electrophoresis. The epithelium forming the pocket lining typically extended into the connective tissue of the pocket wall in the form of a network of finger-like strips. Immunocytological staining indicated that keratins (K) 5, 6, 14 and 19 were expressed by almost all cells of the pocket lining and K13 and K16 by the suprabasal cells. The coronal region of the pocket lining showed some cells staining for K4, Staining for K8 and K18 was seen in the apieal region of the pocket lining and in the finger-like extensions of epithelium into the connective tissue. Compared with normal gingiva, the sulcular and the oral gingival epithelia showed a marked increase in staining for K19. Surprisingly, the pattern of keratin expression of the epithelium of the pocket lining was found to be essentially similar to that of normal junctional epithelium and the anatomical position of the boundaries between each epithelial phenotype were not significantly altered. These patterns of keratin expression were confirmed by the 2D electrophoretic analyses of microdissected regions of epithelium. The potential significance of inflammation to the epithelial changes associated with pocket formation is discussed.     

Expression pattern of adhesion molecules in junctional epithelium differs from that in other gingival epithelia

BACKGROUND AND OBJECTIVE: The gingival epithelium is the physiologically important interface between the bacterially colonized gingival sulcus and periodontal soft and mineralized connective tissues, requiring protection from exposure to bacteria and their products. However, of the three epithelia comprising the gingival epithelium, the junctional epithelium has much wider intercellular spaces than the sulcular epithelium and oral gingival epithelium. Hence, the aim of the present study was to characterize the cell adhesion structure in the junctional epithelium compared with the other two epithelia. MATERIAL AND METHODS: Gingival epithelia excised at therapeutic flap surgery from patients with periodontitis were examined for expression of adhesion molecules by immunofluorescence. RESULTS: In the oral gingival epithelium and sulcular epithelium, but not in the junctional epithelium, desmoglein 1 and 2 in cell-cell contact sites were more abundant in the upper than the suprabasal layers. E-cadherin, the main transmembranous molecule of adherens junctions, was present in spinous layers of the oral gingival epithelium and sulcular epithelium, but was scarce in the junctional epithelium. In contrast, desmoglein 3 and P-cadherin were present in all layers of the junctional epithelium as well as the oral gingival epithelium and sulcular epithelium. Connexin 43 was clearly localized to spinous layers of the oral gingival epithelium, sulcular epithelium and parts of the junctional epithelium. Claudin-1 and occludin were expressed in the cell membranes of a few superficial layers of the oral gingival epithelium. CONCLUSION: These findings indicated that the junctional epithelium contains only a few desmosomes, composed of only desmoglein 3; adherens junctions are probably absent because of defective E-cadherin. Thus, the anchoring junctions connecting junctional epithelium cells are lax, causing widened intercellular spaces. In contrast, the oral gingival epithelium, which has a few tight junctions, functions as a barrier.     

Expression of blood group antigen-related carbohydrates by human gingival epithelia

A panel of monoclonal antibodies was used to examine differentiation-related carbohydrate structures on the surfaces of gingival epithelial cells. The patterns of binding observed indicate distinct differences in the expression of the epitopes examined for three regions of the gingival epithelia corresponding approximately to the regions defined anatomically as the junctional, oral sulcular and oral epithelia. However, epithelium with the staining pattern of oral sulcular epithelium consistently extended beyond the sulcular region to cover the gingival crest and often the uppermost part of the oral aspect of the gingiva. Differential staining of basal and suprabasal cells indicated an unusual pattern of differentiation of the junctional epithelium. The phenotype of this epithelium appears to differ from patterns reported for any other oral epithelium and the possible functional significance of this difference is discussed.     

Rapidly progressive periodontitis combined with plasma cell gingivitis: a case report

A case of rapidly progressive periodontitis combined with plasma cell gingivitis with marked enlargement of the gingiva was presented. Clinically, in the plasma cell gingivitis, the gingiva appear red, friable and bleed easily; usually it does not induce loss of attachment. Histologically, a dense infiltration of the normal plasma cells in the connective tissue is a common finding. A hypersensitivity reaction to some antigens, often flavorings or spices, is generally recognized. In this case, a rapidly progressive loss of attachment was observed, so rapidly progressive periodontitis was diagnosed. Differential diagnosis of the plasma cell gingivitis could be determined by histological and ultrastructural examination. Allergens, however, could not be identified. Conventional periodontal therapy, including intensive plaque control, could not cure the plasma cell gingivitis completely but recurrence of gingival enlargement and loss of attachment could be well controlled.     

Permeability of rodent junctional epithelium to exogenous protein

It has generally been assumed that oral sulcular epithelium, being nonkeratinized, is a vulnerable region which allows bacterial products to pass from the gingival sulcus to the subjacent connective tissue. It has also been suggested that inducing keratinization of the oral sulcular epithelium might create a better barrier to such material. However, this approach ignores the effect of a permeable junctional epithelium, for if exogenous material penetrates this epithelium then the presence of keratinization may be unimportant. Rats possess an orthokeratinized oral sulcular epithelium and so represent what might be considered as an ideal sulcus lining. The protein tracers horseradish peroxidase or microperoxidase were instilled into the gingival sulcus of anesthetized rats. After 1 h, the animals were killed and fixative applied topically and by perfusion. The mandibles were detached, decalcified in EDTA to permit removal at the gingival attachment and sectioning, reacted with diaminobenzidine and H₂O₂ to visualize the tracer, and prepared for light and electron microscopic examination. Controls consisted of: a) animals that had not been treated with horseradish peroxidase, and b) horseradish peroxidase-treated animals incubated without H₂O₂. Microscopic examination revealed penetration of the tracers through the junctional epithelium and into the underlying connective tissue, but never through the adjacent oral sulcular and gingival epithelium. These results suggest that material placed in the sulcus can enter the connective tissue via the junctional epithelium even when the adjacent oral sulcular epithelium forms a keratinized barrier.     

Plaque-induced gingival inflammation in the absence of attached gingiva in dogs

The purpose of this experiment was to evaluate the effect of plaque infection on gingival units (1) with or without support of attached gingiva and (2) with different height of the attachment apparatus. 7 beagle dogs were used. Prior to the initiation of the study 4 different types of "dentogingival" units had been established in each dog by the use of excisional and grafting procedures, namely (1) normal non-operated free gingival units supported by a wide zone of attached gingiva and normal height of the attachment apparatus, (2) regenerated free gingival units supported by loosely attached alveolar mucosa and normal height of the attachment apparatus, (3) regenerated free gingival units supported by loosely attached alveolar mucosa and reduced height of the attachment apparatus and (4) regenerated free gingival units supported by a wide zone of attached gingiva and reduced height of the supporting apparatus. A baseline examination involved assessments of plaque, gingivitis, gingival exudate, probing depth, clinical attachment level, position of the "soft tissue margin" and width of attached gingiva. Following this examination 2 of the dogs were scheduled for biopsy and sacrificed. The remaining 5 dogs were for 40 days placed on a diet regimen which allowed plaque accumulation. The clinical examination was repeated and biopsies sampled at the end of this period. Following preparation the biopsy material was subjected to histometric and morphometric analysis. The results showed that the free gingiva which regenerated following surgical excision of the entire gingiva or following soft tissue grafting, was in most respects, clinically as well as histologically, similar to the "normal" free gingiva. The data obtained after 40 days of plaque accumulation did not reveal any differences between the various "dentogingival" units regarding size and apical extension of the infiltrated portion of the connective tissue. It was concluded that a free gingival unit which is supported by loosely attached alveolar mucosa is not more susceptible to inflammation than a free gingival unit which is supported by a wide zone of attached gingiva.     

Fibrinolytic activity of human gingiva in the presence or absence of plaque bacteria

Activators of fibrinolysis are found in the gingival connective tissue and in the sulcular epithelium. The influence of plaque bacteria and the related inflammatory reaction on the fibrinolytic activity has been evaluated in the human gingiva. An autohistographic technique was applied to sections taken from three groups of 6 specimens each: group A from clinically healthy sites with plaque index = 1 and no bleeding on probing; group B from areas with unambiguous visual signs of gingivitis, with plaque index = 2-3 and bleeding on probing; group C from sites previously treated with professional toothcleaning twice a week for 3 months and with chlorhexidine mouthrinses twice a day for the final 3 wk, in order to obtain a virtually complete elimination of the plaque bacteria. In group C the plaque index was 0 and there was no bleeding on probing. Connective tissue fibrinolytic activity was present in all the sections from the three groups. The sulcular fibrinolytic activity was observed in all the sections taken from the specimens of groups A and B. In contrast, no fibrinolytic activity was observed over the sulcular area in any section taken from the specimens of group C. Therefore, this study does not support previous claims that healthy sulcular epithelium is capable of releasing activators of fibrinolysis. It can be concluded that the presence of any amount of plaque bacteria is associated with sulcular fibrinolytic activity. Contrarily, the elimination of plaque bacteria is associated with the absence of any detectable sign of fibrinolytic activity in the gingival sulcus.     

Endothelial cell leukocyte adhesion molecule-1 (ELAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression in gingival tissue during health and experimentally-induced gingivitis

The changes in vascular adhesion molecule expression and numbers of infiltrating leukocytes during a 21-day experimental gingivitis episode were investigated immunohistochemically. Monoclonal antibodies to ELAM-1 (1.2B6), ICAM-1 (6.5B5), CD3 (OKT3-pan-T cell) and neutrophils (PMN-elastase) were used to identify positive vessels and leukocytes within gingival biopsies taken on d 0, 7, 14 and 21. Vascular endothelium expressed ELAM-1 and ICAM-1 both in clinically 'healthy' tissue (d 0) and in experimentally inflamed tissue (d 7 to 21). Positive vessels were found mainly in the connective tissue subjacent to the junctional epithelium where the highest numbers of T cells and neutrophils were also seen. Although T cells were found in all tissue areas studied, neutrophils were largely concentrated in the junctional epithelium and the subjacent connective tissue but were absent from the oral epithelial region. As the experimental gingivitis developed, the number of T cells or neutrophils in the different tissue regions did not change significantly although the most intense vascular ICAM-1 and ELAM-1 staining redistributed to the CT adjacent to the junctional epithelium. A prominent feature was the intense ICAM-1 positive staining of the junctional epithelium and its absence in the closely adjacent oral epithelium, in both clinically 'healthy' and inflamed tissue. The gradient of ICAM-1 in junctional epithelium, with the strongest staining on the crevicular aspect plus the vascular expression of ELAM-1 and ICAM-1 in both clinically 'healthy' and inflamed tissue may be crucial processes which direct leukocyte migration towards the gingival crevice.     

In situ hybridization study on tissue inhibitors of metalloproteinases (TIMPs) mRNA-expressing cells in human inflamed gingival tissue

This study presents the exact cell types and localization of tissue inhibitors of metalloproteinases (TIMPs) production sites in periodontal diseased gingiva by means of in situ hybridization. Gingival tissue specimens were fixed, embedded and hybridized in situ with specific digoxigenin-labeled cRNA probes (386 and 496 bp). TIMP-1 and -2 mRNAs were expressed on macrophages, mononuclear cells, capillary endothelial cells and some fibroblasts throughout the gingival tissue. In periodontitis, TIMP-1 and -2 mRNA-expressing cells showed significantly different localization. TIMP-1 mRNA was broadly observed in the gingival connective tissue while TIMP-2 mRNA was predominantly expressed in the connective tissue adjacent to the pocket epithelium (p < 0.01). Fewer TIMPs mRNA were observed in minimal gingivitis than in periodontitis, especially in the middle zone of gingival tissue. Thus, TIMP-1 and TIMP-2 mRNA was detected differentially and site-specifically in periodontal diseased gingival tissue.