Immunolocalization of glycosaminoglycans in ageing, healthy and periodontally diseased human cementum

Elevated activity levels do not influence extrinsic fiber attachment morphology on the surface of muscle-attachment sites

Extrinsic fibers (EFs) are a type of penetrating collagenous fiber, closely related to the periodontal ligament, which help anchor soft tissue into bone. These fibers are associated with muscle attachment sites (entheses). Their size and grouping patterns are thought to be indicative of the loading history of the muscle. EFs are of particular significance in anthropology as potential tools for the reconstruction of behavior from skeletal remains and, specifically, entheses. In this study, we used a mouse model to experimentally test how activity level alters the morphology of EF insertion sites on the bone surface of a fibrocartilaginous enthesis, the biceps brachii insertion. Further, we adapted surface metrological techniques from studies of dental wear to perform automated, quantitative and non-destructive analysis of bone surface histology. Our results show that experimentally increased activity had no significant effect on the quantity or density of EF insertions at the enthesis, nor on the size of those insertions. Although EF presence does indicate muscle attachment, activity did not have an observable effect on EF morphology.

Histology of human cementum: Its structure, function, and development

Cementum was first demonstrated by microscopy, about 180 years ago. Since then the biology of cementum has been investigated by the most advanced techniques and equipment at that time in various fields of dental sciences. A great deal of data on cementum histology have been accumulated. These data have been obtained from not only human, but also non-human animals, in particular, rodents such as the mouse and rat. Although many dental histologists have reviewed histology of human cementum, some descriptions are questionable, probably due to incorrect comparison of human and rodent cementum. This review was designed to introduce current histology of human cementum, i.e. its structure, function, and development and to re-examine the most questionable and controversial conclusions made in previous reports.

Effect of proteoglycans at interfaces as related to location, architecture, and mechanical cues

INTRODUCTION

Covalently bound functional GAGs orchestrate tissue mechanics through time-dependent characteristics.

OBJECTIVE

The role of specific glycosaminoglycans (GAGs) at the ligament-cementum and cementum-dentin interfaces within a human periodontal complex were examined. Matrix swelling and resistance to compression under health and modeled diseased states was investigated.

MATERIALS AND METHODS

The presence of keratin sulfate (KS) and chondroitin sulfate (CS) GAGs at the ligament-cementum and cementum-dentin interfaces in human molars (N=5) was illustrated by using enzymes, atomic force microscopy (AFM), and AFM-based nanoindentation. The change in physical characteristics of modeled diseased states through sequential digestion of keratin sulfate (KS) and chondroitin sulfate (CS) GAGs was investigated. One-way ANOVA tests with P<0.05 were performed to determine significant differences between groups. Additionally, the presence of mineral within the seemingly hygroscopic interfaces was investigated using transmission electron microscopy.

RESULTS

Immunohistochemistry (N=3) indicated presence of biglycan and fibromodulin small leucine rich proteoglycans at the interfaces. Digestion of matrices with enzymes confirmed the presence of KS and CS GAGs at the interfaces by illustrating a change in tissue architecture and mechanics. A significant increase in height (nm), decrease in elastic modulus (GPa), and tissue deformation rate (nm/s) of the PDL-C attachment site (215±63-424±94nm; 1.5±0.7-0.4±0.2GPa; 21±7-48±22nm/s), and cementum-dentin interface (122±69-360±159nm; 2.9±1.3-0.7±0.3GPa; 18±4-30±6nm/s) was observed.

CONCLUSIONS

The sequential removal of GAGs indicated loss in intricate structural hierarchy of hygroscopic interfaces. From a mechanics perspective, GAGs provide tissue recovery/resilience. The results of this study provide insights into the role of GAGs toward conserved tooth movement in the socket in response to mechanical loads, and modulation of potentially deleterious strain at tissue interfaces.

Chondroitin sulphate (WF6 epitope) levels in peri-miniscrew implant crevicular fluid during orthodontic loading

The aim of this study was to monitor changes in chondroitin sulphate (CS; WF6 epitope) levels in peri-miniscrew implant crevicular fluid (PMICF) during orthodontic loading. Ten patients (seven males and three females; aged 22.0 +/- 3.4 years), who required orthodontic treatment with extraction of all four premolar teeth, participated in the study. Twenty miniscrew implants (used as orthodontic anchorage) were placed, two in each patient, buccally and bilaterally in the alveolar bone between the roots of the maxillary posterior teeth. Sentalloy closed-coil springs (50 g) were used to load the miniscrew implants and to move the maxillary canines distally. During the unloaded period, PMICF samples were collected on days 1, 3, 5, and 7 after miniscrew implant placement and on days 14, 21, 28, and 35 during the loaded period. Clinical mobility assessments of the miniscrew implants were recorded at each visit. The competitive enzyme-linked immunosorbent assay with monoclonal antibody WF6 was used to detect CS (WF6 epitope) levels in the PMICF samples. The differences between the CS (WF6 epitope) levels during the unloaded and loaded periods were determined by a Mann-Whitney U-test. During the loaded period, two miniscrew implants were considered to have failed. The CS (WF6 epitope) levels during the unloaded period ranged from 0.00 to 758.03 ng/ml and those during the loaded period from 0.00 to 1025.11 ng/ml. Medians of CS (WF6 epitope) levels, around 'immobile' miniscrew implants, between the unloaded and loaded periods were not significantly different (P = 0.07). CS (WF6 epitope) levels in PMICF can be detected and may be used as biomarkers for assessing alveolar bone remodelling around miniscrew implants during orthodontic loading.

An immunohistochemical study of the extracellular matrix of entheses associated with the human pisiform bone

The immunohistochemical labelling patterns of the extracellular matrix at the insertion of the flexor carpi ulnaris tendon and the entheses at both ends of the pisometacarpal and pisohamate ligaments were compared in order to relate the molecular composition of the attachment sites to their mechanical environment. Tissue was obtained from elderly dissecting room cadavers and labelled with a panel of monoclonal antibodies directed against collagens, glycosaminoglycans, proteoglycans and matrix proteins. All entheses were fibrocartilaginous and labelled positively for molecules typically associated with articular cartilage (type II collagen, chondroitin 6 sulphate, aggrecan and link protein). Labelling for type II collagen was most conspicuous at the attachment of the flexor carpi ulnaris tendon. In the ligaments, type II collagen labelling was always greater at the pisiform end. Matrilin 1 was universally present at all five entheses examined and fibromodulin labelling was most intense around the tidemark. Fibromodulin may thus be involved in anchorage and/or the control of mineralization at the hard-soft tissue interface of entheses. The greater prominence of fibrocartilage at the pisiform enthesis of the flexor carpi ulnaris tendon than at any ligament attachment may relate to the marked change in the tendon insertional angle that occurs with wrist movements. We also suggest that the more fibrocartilaginous character of the proximal compared with the distal ends of the ligaments relates to the fact that the pisiform is anchored in position and is thus at the centre of rotation of any movement of ligaments attached to it.

Confocal laser scanning microscopy of human cementocytes: Analysis of three-dimensional image reconstruction

In order to define a practical method for a quantitative-qualitative analysis of dental hard tissue cells, we have studied cementocytes of human teeth using Confocal Laser Scanning Microscopy (CLSM), a research technique based on laser light microscopic analysis of biological samples stained for fluorescence observation. One thousand and eight hundred cementocyte images were analyzed. CLSM allowed improved tissue imaging, bi-dimensional pictures with better resolution at cellular level and, in particular, the possibility of a three-dimensional image reconstruction, thus providing a dynamic view of the cell under different situations. CLSM allowed a careful morphological observation and dimensional analysis of cementocytes at cellular resolution: cementocyte dimensional parameters like cell body without cell processes, cell dimensions with cell processes, and the number of cellular processes could be obtained. In conclusion, this study reports the fine definition of cementocytes at microscopic level by CSLM and the results warrant the use of this technique for further comparative analyses between normal and pathological cementocyte cells, e.g. cementum neoplasia and periodontal disease which still await a clear analytical description at cellular level.

The cementum-dentin junction also contains glycosaminoglycans and collagen fibrils

The presence of glycosaminoglycans (GAGs) and their contribution to mechanical properties of the cementum-dentin junction (CDJ) were investigated using nanometer scale characterization techniques. Five to two millimeter thick transverse sections from the apical ends of human molars were ultrasectioned at room temperature under wet conditions using a diamond knife and an ultramicrotome. The structure of the CDJ under dry and wet conditions before and after digestion of GAGs and collagen fibrils was studied using an atomic force microscope (AFM). The mechanical properties of the untreated and enzyme treated CDJ under wet conditions were studied using an AFM-based nanoindenter. GAG digestion was performed for 1, 3, and 5 h at 37 degrees C using chondroitinase-ABC. Collagen fibril digestion was performed for 24 and 48 h at 37 degrees C using collagenase. As reported previously, AFM scans of dry untreated CDJ (control) revealed a valley, which transformed into a peak under wet conditions. The height differences relative to cementum and dentin of untreated and treated CDJ were determined by measuring the CDJ profile under dry and wet conditions. The depth of the valley of GAG and collagen-digested CDJ was greater than that of undigested CDJ under dry conditions. The height of the peak of GAG-digested CDJ was significantly higher than that of the undigested CDJ under wet conditions. The collagen-digested CDJ under wet conditions is assumed to form a valley because of the removal of collagen fibrils from the CDJ. However, the depth of the valley was lower compared to the depth under dry conditions. Wet AFM-based nanoindentation showed that the elastic modulus and hardness of control (3.3+/-1.2 and 0.08+/-0.03 GPa) were significantly higher (ANOVA & SNK, P < 0.05) than chondroitinase-ABC treated CDJ (0.9+/-0.4 and 0.02+/-0.004 GPa) and collagenase treated CDJ (1.5+/-0.6 and 0.04+/-0.01 GPa). No significant difference in mechanical properties between chondroitinase-ABC and collagenase treated CDJ was observed. Based on the results it was concluded that the 10-50 microm wide CDJ is a composite that includes, chondroitin-4-sulfate, chondroitin-6-sulfate, and possibly dermatan sulfate, and collagen fibrils. The association of GAGs with the collagen fibrils provides the observed controlled hydration and partially contributes toward the stiffness of the CDJ under wet conditions.

Marker of cemento-periodontal ligament junction associated with periodontal regeneration

OBJECTIVE

The purpose of this study was to identify factors promoting formation of the cemento-periodontal ligament junction.

BACKGROUND

Regeneration of the cemento-periodontal ligament junction is an important factor in recovery of the connective tissue attachment to the cementum and it is important to identify all specific substances that promote its formation. To clarify the substances involved in cemento-periodontal ligament junction formation, we produced a monoclonal antibody (mAb) to human cemento-periodontal ligament junction (designated as the anti-TAP mAb) and examined its immunostaining properties and reactive antigen.

METHODS

Hybridomas producing monoclonal antibody against human cemento-periodontal ligament junction antigens were established by fusing P3U1 mouse myeloma cells with spleen cells from BALB/c mice immunized with homogenized human cemento-periodontal ligament junction. The mAb, the anti-TAP mAb for cemento-periodontal ligament junction, was then isolated. The immunoglobulin class and light chain of the mAb were examined using an isotyping kit. Before immunostaining, antigen determination using an enzymatic method or heating was conducted. Human teeth, hard tissue-forming lesions, and animal tissues were immunostained by the anti-TAP mAb.

RESULTS

The anti-TAP mAb was positive in human cemento-periodontal ligament junction and predentin but negative in all other human and animal tissues examined. In the cemento-osseous lesions, the anti-TAP mAb was positive in the peripheral area of the cementum and cementum-like hard tissues and not in the bone and bone-like tissues. The anti-TAP mAb showed IgM (kappa) and recognized phosphoprotein.

CONCLUSION

The anti-TAP mAb is potentially useful for developing new agents promoting cementogenesis and periodontal regeneration.

Immunohistochemical localization and expression of fibromodulin in adult rat periodontium and inflamed human gingiva

OBJECTIVE

The aim of this study was to determine the distribution and expression of fibromodulin in adult rat periodontal tissues and inflamed human gingiva.

MATERIALS AND METHODS

The distribution of fibromodulin in rat molar periodontium and human gingival tissue was studied by immunohistochemistry. The expression of fibromodulin mRNA from human gingival fibroblasts, periodontal ligament fibroblasts and osteoblasts was studied by reverse transcription-polymerase chain reaction (RT-PCR). For comparative purposes, the distribution and mRNA expression of collagen types I and III, as well as the two small leucine-rich proteoglycans decorin and biglycan were also studied.

RESULTS

In the adult rat periodontium, fibromodulin was distributed in the suprabasal gingival epithelium, gingival and periodontal fibroblasts as well as their surrounding extracellular matrices. Strong expression was noted in the palatal gingival tissues and the interfaces of the periodontal ligament with alveolar bone and cementum. In human gingival tissues, staining of fibromodulin was detected in the connective tissue of inflamed gingiva associated with both gingivitis and periodontitis; whereas, weak staining for this molecule was noted in healthy gingival tissues. The expression of mRNA for fibromodulin was strongest in the cultured osteoblasts. Periodontal ligament fibroblasts showed only a weak level of expression for fibromodulin mRNA.

CONCLUSIONS

Fibromodulin is differentially expressed throughout the periodontium being primarily associated with collagen type I in non-mineralized sites. In addition fibromodulin showed an upregulation in inflamed gingival tissue.

Immunohistochemical localization of fibromodulin in the periodontium during cementogenesis and root formation in the rat molar

BACKGROUND

Cementum is essential for periodontal regeneration, as it provides anchorage between the root surface and the periodontal ligament. A variety of macromolecules present in the extracellular matrix of the periodontium, including proteoglycans, are likely to play a regulatory role in cementogenesis. Recently, the small leucine-rich proteoglycan, fibromodulin, has been isolated from bovine periodontal ligament and localized in bovine cementum, as well as in human periodontal ligament.

OBJECTIVE

The aim of this study was to examine the distribution of fibromodulin during cementogenesis and root formation.

METHODS

A standard indirect immunoperoxidase technique was employed, using an antifibromodulin polyclonal antibody on sections of molar teeth from rats aged 3, 5 and 8 weeks.

RESULTS

Immunoreactivity to fibromodulin was evident in the periodontal ligament in all sections. An intense positive stain was observed in the extracellular matrix where the periodontal ligament fibers insert into the alveolar bone and where the Sharpey's fibers insert into the cementum. There was no staining evident in the mineralized cellular and acellular cementum. The intensity of immunoreactivity to the antifibromodulin antibody increased proportionally with increasing tissue maturation.

CONCLUSION

The results from this study suggest that fibromodulin is a significant component of the extracellular matrix in the periodontal ligament during development, and may play a regulatory role in the mineralization process or maintaining homeostasis at the hard-soft tissue interface during cementogenesis.

Differential distribution of glycosaminoglycans in human cementifying fibroma and fibro-osseous lesions

OBJECTIVE

Differential diagnosis of cementifying fibroma, ossifying fibroma and fibrous dysplasia by histological evaluation is often difficult. The aim of this study was to examine the immunoreactivities for keratan sulfate (KS) and chondroitin-4-sulfate (C4S) glycosaminoglycans of the histological samples obtained from mandibles of patients with these diseases.

MATERIALS AND METHODS

The samples were collected from three patients with cementifying fibroma, two with ossifying fibroma and three with fibrous dysplasia and were subjected to immunohistochemical analyses.

RESULTS

The results demonstrated that a significant immunoreactivity for KS was found in lacunae housing cells in the cementum-particles of cementifying fibromas, while both ossifying fibromas and fibrous dysplasias showed no significant immunoreactivity for KS. For C4S, while the former showed little immunoreactivity, the latter two cases exhibited intensive immunostaining in the pre- and poorly mineralized matrices.

CONCLUSIONS

These results suggest that cementifying fibromas could be distinguished from these fibro-osseous tumors by using immunohistochemical analysis for KS and C4S.

The skeletal attachment of tendons--tendon "entheses"

Tendon entheses can be classed as fibrous or fibrocartilaginous according to the tissue present at the skeletal attachment site. The former can be "bony" or "periosteal", depending on whether the tendon is directly attached to bone or indirectly to it via the periosteum. At fibrocartilaginous entheses, the uncalcified fibrocartilage dissipates collagen fibre bending and tendon narrowing away from the tidemark; calcified fibrocartilage anchors the tendon to the bone and creates a diffusion barrier between the two. Where there are additional fibrocartilaginous specialisations in the tendon and/or bone next to the enthesis, an "enthesis organ" is created that reduces wear and tear. Little attention has been paid to bone at entheses, despite the obvious bearing this has on the mechanical properties of the interface and the clinical importance of avulsion fractures. Disorders at entheses (enthesopathies) are common and occur in conditions such as diffuse idiopathic skeletal hyperostosis and the seronegative spondyloarthropathies. They are also commonly seen as sporting injuries such as tennis elbow and jumper's knee.

Proteoglycans and orthodontic tooth movement

Proteoglycans represent an important and diverse family of extracellular matrix components within the connective tissues of the periodontium. This review focuses on the function and metabolism of the various proteoglycans in periodontal tissues, such as alveolar bone and periodontal ligament, and considers their potential fate in response to an orthodontic force. Such considerations provide an important background in evaluating the potential for proteoglycan metabolites, alongside other connective tissue metabolites, as biomarkers for assessing the deep-seated metabolic changes and as a diagnostic tool in monitoring orthodontic tooth movement.

A histological and electron-microscopic study of the architecture and ultrastructure of human periodontal tissues

The structure of periodontal tissues is still far less understood than their clinical relevance would demand. Here the periodontal ligament and radicular cementum in healthy human teeth were studied by light microscopy, transmission and scanning electron microscopy. These observations showed that the extracellular matrix of periodontal ligament is composed of a loose plexus of wavy collagen fibrils immersed in a highly hydrated interfibrillar matrix. Only close to their cemental insertion do these fibrils gather in thick, parallel fascicles (Sharpey's fibres). As these cross the mineralization front, they become infiltrated by the mineral phase and continue directly with the cementum matrix. Sharpey's fibres, "extrinsic" and "intrinsic" fibres all appear to be the same fibres, which bend and branch repeatedly during their course within the thickness of the cementum. Because of its physical continuity with the cementum, a limited portion of the periodontal ligament approximately corresponding to the length of Sharpey's fibres remains unaffected by enzymatic digestion of the interfibrillar matrix while the rest of the ligament is completely dissolved. The findings here indicate that the periodontal ligament and dental cementum join by a continuity rather than a contiguity of structures; that the collagen-mineral relation in cementum has distinctive features in comparison to other hard tissues; that extrinsic and intrinsic fibres of cementum and the adjoining portion of periodontal ligament form a structural, mechanical and metabolic unit distinct from the central, more metabolically active portion of the periodontal ligament.

Stromelysin-1 (MMP-3) in forming enamel and predentine in rat incisor-coordinated distribution with proteoglycans suggests a functional role

Stromelysin-1 (matrix metalloproteinase-3) or proteoglycanase was visualized by light and electron microscopy immunolabelling in the forming zone of rat incisors. In predentine, labelling was more dense at the transition zone between the inner proximal third and the two outer thirds. Odontoblast processes were also positively stained, mostly in predentine and to a lesser degree in dentine. The dentine-enamel junction was intensely labelled, whereas dentine and forming enamel were only faintly stained. Gold-antibodies complexes were seen inside secretory ameloblasts and odontoblasts in cytosolic locations. The distribution of stromelysin-1 was compared with the distribution of 2-B-6 epitope, an antibody recognizing chondroitin-4-sulphate/dermatan sulphate and which showed a decreasing gradient from the proximal zone to the distal part of predentine. In contrast, both 5-D-4, an anti-keratan sulphate antibody and an anti-lumican antibody displayed a reversed distribution, with an increase seen from the proximal and central thirds to the distal part of predentine. This coordinated distribution suggests that stromelysin-1 may have a functional role, being implicated in predentine in the degradation of chondroitin-4-sulphate/dermatan sulphate-containing proteoglycans, and consequently allowing keratan sulphate proteoglycan concentration to increase near the border where mineralization is initiated.

The proteoglycans of human cementum: immunohistochemical localization in healthy, periodontally involved and ageing teeth

Cementum is believed to play a regulatory role in periodontal regeneration through a variety of macromolecules present in its extracellular matrix (ECM), among which are the proteoglycans (PG). The PG of human cementum have not been fully characterized. This study has used a standard indirect immunoperoxidase technique to investigate the presence and distribution of PG species within the ECM of human cementum. Freshly extracted human permanent teeth were separated into 8 age groups; each group was subdivided to include healthy and periodontally involved teeth, which were then fixed, demineralized and wax-embedded. Sections were incubated with polyclonal antibodies recognizing protein core epitopes in the large chondroitin sulphate PG versican and the small interstitial PG decorin, biglycan, fibromodulin and lumican. Immunoreactivity to versican, decorin, biglycan and lumican was evident at the borders and lumina of a proportion of lacunae and canaliculi surrounding cementocytes in cellular cementum, as well as on inserted periodontal ligament (PDL) fibres. Biglycan was also present along incremental lines in cellular cementum, whereas staining for fibromodulin was negative. In acellular cementum, no immunoreactivity was evident with any of the antibodies used except on inserted PDL fibres. These results indicate that versican, decorin, biglycan and lumican are components of the ECM of cellular, but not of acellular cementum. Neither age nor periodontal diseases appear to qualitatively influence the PG population of cementum. The distribution of PG epitopes around a proportion of cementocytes suggests the existence of different cementocyte subpopulations, or a differential response of these cells to yet undefined stimuli.