Immunohistological localization of cell adhesion proteins and integrins in the periodontium

Dual peptide-functionalized hydrogels differentially control periodontal cell function and promote tissue regeneration

Restoring the tooth-supporting tissues lost during periodontitis is a significant clinical challenge, despite advances in both biomaterial and cell-based approaches. This study investigated poly(ethylene glycol) (PEG) hydrogels functionalized with integrin-binding peptides RGD and GFOGER for controlling periodontal ligament cell (PDLC) activity and promoting periodontal tissue regeneration. Dual presentation of RGD and GFOGER within PEG hydrogels potentiated two key PDLC functions, alkaline phosphatase (ALP) activity and matrix mineralization, over either peptide alone and could be tuned to differentially promote each function. Hydrogel matrix mineralization, fostered by high concentrations of GFOGER together with RGD, identified a PDLC phenotype with accelerated matrix adhesion formation and expression of cementoblast and osteoblast genes. In contrast, maximizing ALP activity through high RGD and low GFOGER levels resulted in minimal hydrogel mineralization, in part, through altered PDLC pyrophosphate regulation. Transplantation of PDLCs in hydrogels optimized for either outcome promoted cementum formation in rat periodontal defects; however, only hydrogels optimized for in vitro mineralization improved new bone formation. Overall, these results highlight the utility of engineered hydrogel systems for controlling PDLC functions and their promise for promoting periodontal tissue regeneration.

Bacterial adhesion to collagens: implications for biofilm formation and disease progression in the oral cavity

Collagen is the most abundant structural protein in the body and the main component of the extracellular matrix of most tissues, including dentine and periodontal tissues. Despite the well-characterized role of collagen and specifically type-I collagen, as a ligand for host cells, its role as a substrate for bacterial adhesion and biofilm formation is less explored. Therefore, the purpose of this review is to discuss recent findings regarding the adhesion of oral bacteria to collagen surfaces and its role in the progression and severity of oral and systemic diseases. Initial oral colonizers such as streptococci have evolved collagen-binding proteins (cbp) that are important for the colonization of dentine and periodontal tissues. Also, periodontal pathogens such as Porphyromonas gingivalis and Tannerella forsythia utilise cbps for tissue sensing and subsequent invasion. The implications of bacteria-collagen coupling in the context of collagen biomaterials and regenerative dentistry approaches are also addressed. Furthermore, the importance of interdisciplinary techniques such as atomic force microscopy for the nanocharacterization of bacteria-collagen interactions is also considered. Overall, understanding the process of oral bacterial adhesion onto collagen is important for developing future therapeutic approaches against oral and systemic diseases, by modulating the early stages of biofilm formation.

Telmisartan Prevents Alveolar Bone Loss by Decreasing the Expression of Osteoclasts Markers in Hypertensive Rats With Periodontal Disease

Periodontal disease (PD) is a prevalent inflammatory disease with the most severe consequence being the loss of the alveolar bone and teeth. We therefore aimed to evaluate the effects of telmisartan (TELM), an angiotensin II type 1 receptor (Agtr1) antagonist, on the PD-induced alveolar bone loss, in Wistar (W) and Spontaneous Hypertensive Rats (SHRs). PD was induced by ligating the lower first molars with silk, and 10 mg/kg TELM was concomitantly administered for 15 days. The hemimandibles were subjected to microtomography, ELISA was used for detecting tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), CXCL3, and CCL2, while qRT-PCR was used for analyzing expression of components of renin-angiotensin system (RAS) (Agt, Ace, Agt1r, Agt2r, Ace2, and Masr), and bone markers (Runx2, Osx, Catnb, Alp, Col1a1, Opn, Ocn, Bsp, Bmp2, Trap, Rank, Rankl, CtsK, Mmp-2, Mmp-9, and osteoclast-associated receptor (Oscar)). The SHR + PD group showed greater alveolar bone loss than the W + PD group, what was significantly inhibited by treatment with TELM, especially in the SHR group. Additionally, TELM reduced the production of TNF-α, IL-1β, and CXCL3 in the SHR group. The expression of Agt increased in the groups with PD, while Agtr2 reduced, and TELM reduced the expression of Agtr1 and increased the expression of Agtr2, in W and SHRs. PD did not induce major changes in the expression of bone formation markers, except for the expression of Alp, which decreased in the PD groups. The bone resorption markers expression, Mmp9, Ctsk, and Vtn, was higher in the SHR + PD group, compared to the respective control and W + PD group. However, TELM attenuated these changes and increased the expression of Runx2 and Alp. Our study suggested that TELM has a protective effect on the progression of PD, especially in hypertensive animals, as evaluated by the resorption of the lower alveolar bone. This can be partly explained by the modulation in the expression of Angiotensin II receptors (AT1R and AT2R), reduced production of inflammatory mediators, the reduced expression of resorption markers, and the increased expression of the bone formation markers.

A proof of concept gene-activated titanium surface for oral implantology applications

Dental implants are very successful medical devices, yet implant failures do occur due to biological and mechanical complications. Peri-implantitis is one such biological complication that is primarily caused by bacteria and their products at the implant soft tissue interface. Bacterial infiltration can be prevented by the formation of a reliable soft tissue seal encircling dental implants. Platelet-derived growth factor-BB (PDGF-BB) has significant chemotactic and proliferative effects on various mesenchymal cell types, including fibroblasts, and therefore can be an effective molecule to enhance the peri-implant soft tissue seal. To overcome the limitations of the recombinant protein form of PDGF-BB, such as cost and the need for supraphysiological doses, we have developed and characterized a titanium surface that is rendered bioactive by coating it with polyethylenimine-plasmid DNA (pDNA) nanoplexes in the presence of sucrose. Human embryonic kidney 293T (HEK293T) cells and human primary gingival fibroblasts (GFs) were successfully transfected in culture with enhanced green fluorescent protein (EGFP)-encoding pDNA or platelet-derived growth factor subunit B (PDGFB)-encoding pDNA loaded into nanoplexes and coated onto titanium disks in a dose-dependent manner. GFs were shown to secrete PDGF-BB for at least 7 days after transfection and displayed both minimal viability loss and increased integrin-α2 expression 4 days posttransfection.

Induction of migration of periodontal ligament cells by selective regulation of integrin subunits

The recruitment of tissue-resident stem cells is important for wound regeneration. Periodontal ligament cells (PDL cells) are heterogeneous cell populations with stemness features that migrate into wound sites to regenerate periodontal fibres and neighbouring hard tissues. Cell migration is regulated by the local microenvironment, coordinated by growth factors and the extracellular matrix (ECM). Integrin-mediated cell adhesion to the ECM provides essential signals for migration. We hypothesized that PDL cell migration could be enhanced by selective expression of integrins. The migration of primary cultured PDL cells was induced by platelet-derived growth factor-BB (PDGF-BB). The effects of blocking specific integrins on migration and ECM adhesion were investigated based on the integrin expression profiles observed during migration. Up-regulation of integrins α3, α5, and fibronectin was identified at distinct localizations in migrating PDL cells. Treatment with anti-integrin α5 antibodies inhibited PDL cell migration. Treatment with anti-integrin α3, α3-blocking peptide, and α3 siRNA significantly enhanced cell migration, comparable to treatment with PDGF-BB. Furthermore, integrin α3 inhibition preferentially enhanced adhesion to fibronectin via integrin α5. These findings indicate that PDL cell migration is reciprocally regulated by integrin α3-mediated inhibition and α5-mediated promotion. Thus, targeting integrin expression is a possible therapeutic strategy for periodontal regeneration.

Are Cementoblasts a Subpopulation of Osteoblasts or a Unique Phenotype?

Experimental studies have shown a great potential for periodontal regeneration. The limitations of periodontal regeneration largely depend on the regenerative potential at the root surface. Cellular intrinsic fiber cementum (CIFC), so-called bone-like tissue, may form instead of the desired acellular extrinsic fiber cementum (AEFC), and the interfacial tissue bonding may be weak. The periodontal ligament harbors progenitor cells that can differentiate into periodontal ligament fibroblasts, osteoblasts, and cementoblasts, but their precise location is unknown. It is also not known whether osteoblasts and cementoblasts arise from a common precursor cell line, or whether distinct precursor cell lines exist. Thus, there is limited knowledge about how cell diversity evolves in the space between the developing root and the alveolar bone. This review supports the hypothesis that AEFC is a unique tissue, while CIFC and bone share some similarities. Morphologically, functionally, and biochemically, however, CIFC is distinctly different from any bone type. There are several lines of evidence to propose that cementoblasts that produce both AEFC and CIFC are unique phenotypes that are unrelated to osteoblasts. Cementum attachment protein appears to be cementum-specific, and the expression of two proteoglycans, fibromodulin and lumican, appears to be stronger in CIFC than in bone. A theory is presented that may help explain how cell diversity evolves in the periodontal ligament. It proposes that Hertwig’s epithelial root sheath and cells derived from it play an essential role in the development and maintenance of the periodontium. The role of enamel matrix proteins in cementoblast and osteoblast differentiation and their potential use for tissue engineering are discussed.

Immunohistochemical localization of tenascin-C in rat periodontal ligament with reference to alveolar bone remodeling

We investigated the immunohistochemical localization of tenascin-C in 8-week-old rat periodontal ligaments. Tenascin-C immunoreactivity was detected in zones along with cementum and alveolar bone, and more intensely on the resorption surface of alveolar bone than on the formation surface. On the resorbing surface, tenascin-C immunoreactivity was detected in Howship's lacunae without osteoclasts, and in the interfibrous space of the periodontal ligaments, indicating that this molecule works as an adhesion molecule between bone and fibers of periodontal ligaments. Upon experimental tooth movement by inserting elastic bands (Waldo method), the physiological resorption surface of alveolar bone under compressive force showed enhanced bone resorption and enhanced tenascin-C immunoreactivity. However, on the physiological bone formation surface under compressive force, bone resorption was seen only occasionally, and no enhanced tenascin-C immunoreactivity was noted. In an experiment involving excessive occlusal loading to rat molars, transient bone resorption occurred within interradicular septa, but no enhanced tenascin-C immunoreactivity was seen in the periodontal ligaments. These results indicate that tenascin-C works effectively on the bone resorbing surface of physiological alveolar bone remodeling sites, rather than on the non-physiological transient bone resorbing surface. Fibronectin immunoreactivity was distributed evenly in the periodontal ligaments under experimental conditions. Co-localization of tenascin-C and fibronectin immunoreactivity was observed in many regions, but mutually exclusive expression patterns were also seen in some regions, indicating that fibronectin might not be directly involved in alveolar bone remodeling, but may play a role via interaction with tenascin-C.

Prospective potency of TGF-β1 on maintenance and regeneration of periodontal tissue

Periodontal ligament (PDL) tissue, central in the periodontium, plays crucial roles in sustaining tooth in the bone socket. Irreparable damages of this tissue provoke tooth loss, causing a decreased quality of life. The question arises as to how PDL tissue is maintained or how the lost PDL tissue can be regenerated. Stem cells included in PDL tissue (PDLSCs) are widely accepted to have the potential to maintain or regenerate the periodontium, but PDLSCs are very few in number. In recent studies, undifferentiated clonal human PDL cell lines were developed to elucidate the applicable potentials of PDLSCs for the periodontal regenerative medicine based on cell-based tissue engineering. In addition, it has been suggested that transforming growth factor-beta 1 is an eligible factor for the maintenance and regeneration of PDL tissue.

Sandblasted-acid-etched titanium surface influences in vitro the biological behavior of SaOS-2 human osteoblast-like cells

Osseointegrated dental implants have been successfully used over the past several years, allowing functional replacement of missing teeth. Surface properties of titanium dental implants influence bone cell response. Implant topography appears to modulate cell growth and differentiation of osteoblasts thus affecting the bone healing process. Optimal roughness and superficial morphology are still controversial and need to be clearly defined. In the present study we evaluated in vitro the biological behavior of SaOS-2 cells, a human osteoblast-like cell line, cultured on two different titanium surfaces, smooth and sandblasted-acid-etched, by investigating cell morphology, adhesion, proliferation, expression of some bone differentiation markers and extracellular matrix components. Results showed that the surface topography may influence in vitro the phenotypical expression of human osteoblast-like cells. In particular the tested sandblasted-acid-etched titanium surface induced a significantly increased Co I deposition and α2-β1 receptor expression as compared to the relatively smooth surface, promoting a probable tendency of SaOS-2 cells to shift toward a mature osteoblastic phenotype. It is therefore likely that specific surface properties of sandblasted-acid-etched titanium implants may modulate the biological behavior of osteoblasts during bone tissue healing.

Advanced glycation of type I collagen and fibronectin modifies periodontal cell behavior

BACKGROUND

Advanced glycation end products (AGEs) have been linked to pathogenic mechanisms of diabetes mellitus. However, little is known about the contribution of protein glycation to periodontal disease in patients with diabetes. Therefore, this study investigated whether glycation of type I collagen (COLI) and fibronectin (FN) modified the behavior of human gingival fibroblasts (hGFs) and periodontal ligament fibroblasts (hPDLs).

METHODS

Procedures for rapid in vitro glycation of COLI and FN used methylglyoxal (MG). Formation of AGEs was analyzed by changes in protein migration using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting with antibodies specific for MG-glycated proteins. Experiments then characterized the effects of glycated FN and COLI on the behavior of hGFs and hPDLs.

RESULTS

MG glycated COLI and FN in <6 hours. Confirming the specificity of the reactions, antibodies specific for MG-induced AGEs reacted with glycated FN and COLI but not with control proteins. In cell culture experiments, glycated FN was significantly less efficient in supporting the attachment of hGFs and hPDLs (P <0.05). Moreover, the morphologic parameters, including length, area, perimeter, and shape factor, were altered (P <0.001) for cells on both glycated proteins. Finally, cell migration was reduced on glycated FN and COLI (P <0.001).

CONCLUSIONS

MG treatment efficiently glycated COLI and FN, providing a new tool to study the effects of diabetes on periodontal disease. The substantial effects of glycated COLI and FN on hGF and hPDL behavior indicated that protein glycation contributed to the pathogenesis and altered periodontal wound healing observed in patients with diabetes.

A simple cell motility assay demonstrates differential motility of human periodontal ligament fibroblasts, gingival fibroblasts, and pre-osteoblasts

During periodontal regeneration, multiple cell types can invade the wound site, thereby leading to repair. Cell motility requires interactions mediated by integrin receptors for the extracellular matrix (ECM), which might be useful in guiding specific cell populations into the periodontal defect. Our data demonstrate that fibroblasts exhibit differential motility when grown on ECM proteins. Specifically, gingival fibroblasts are twice as motile as periodontal ligament fibroblasts, whereas osteoblasts are essentially non-motile. Collagens promote the greatest motility of gingival fibroblasts in the following order: collagen III>collagen V>collagen I. Differences in motility do not correlate with cell proliferation or integrin expression. Osteoblasts display greater attachment to collagens than does either fibroblast population, but lower motility. Gingival fibroblast motility on collagen I is generally mediated by alpha2 integrins, whereas motility on collagen III involves alpha1 integrins. Other integrins (alpha10 or alpha11) may also contribute to gingival fibroblast motility. Thus, ECM proteins do indeed differentially promote the cell motility of periodontal cells. Because of their greater motility, gingival fibroblasts have more of a potential to invade periodontal wound sites and to contribute to regeneration. This finding may explain the formation of disorganized connective tissue masses rather than the occurrence of the true regeneration of the periodontium.

Human gingival fibroblast integrin subunit expression on titanium implant surfaces

BACKGROUND

Implant surface characteristics have been shown to modify cell behavior and regulate integrin expression. Integrin expression and resultant integrin-mediated cellular activity are essential components of tissue healing and homeostasis. Although both osseous and soft tissue healing around dental implants are critical to clinical success, there is limited information available on the effect of implant surfaces on integrin expression in soft tissues. Therefore, the aim of this study was to examine integrin expression for gingival fibroblasts on titanium surfaces and the influence of titanium surface roughness on integrin expression and cell morphology.

METHODS

Human gingival fibroblasts were cultured on smooth (polished) and rough (sand-blasted acid-etched) titanium surfaces and a cell culture plastic (control) surface. To analyze integrin expression, total RNA was isolated from experimental and control cells, and levels of integrin subunit mRNA were assessed by reverse transcription-polymerase chain reaction (RT-PCR) using primers specific for the alpha2, alpha4, alpha5, alpha(v), and beta1 integrin subunits and aldolase (internal control). PCR products were analyzed by polyacrylamide gel electrophoresis (PAGE), confirmed via DNA sequencing, and quantified using computer-assisted densitometry. The expression of the integrin subunits was analyzed at the protein level using flow cytometry, as well as fluorescence and confocal laser microscopy. Cell morphology was evaluated using scanning electron microscopy (SEM).

RESULTS

Our experiments demonstrated cellular expression of the alpha2, alpha4, alpha5, alpha(v), and beta1 integrin subunits at both mRNA and protein levels on all surfaces. In addition, the alpha4 and beta1 mRNA levels were significantly increased on smooth titanium relative to plastic surfaces (P <.05) with intermediate mRNA levels found on the rough titanium surfaces. The smooth titanium surfaces exhibited a flat monolayer of cells, while rough titanium surfaces showed cells orienting themselves along surface irregularities.

CONCLUSIONS

These results demonstrate the presence of multiple integrin subunits in human gingival fibroblasts grown in contact with titanium implant surfaces and that titanium surface roughness alters cellular morphology but appears to have limited effects on integrin expression. This study provides insight into the complicated cellular and molecular events occurring at the implant surface that may be critical to optimizing the soft tissue interactions with the soft tissue-implant interface.

AlphaVbeta3 integrin ligands enhance volume-sensitive calcium influx in mechanically stretched osteocytes

We propose that specific osteocyte-matrix interactions regulate the volume-sensitive calcium influx pathway, which we have shown is mediated by stretch-activated cation channels (SA-Cat) and is essential for the stretch-activated anabolic response in bone. The current study measured the hypotonic swelling-induced increase in cytosolic calcium concentration, [Ca(2+)](i), in rat osteocytes, and found that cells adherent to different matrices behave differently. Osteopontin and vitronectin, matrix molecules that bind the alpha(V)beta(3) integrin, induced larger responses to the hypotonic swelling than other matrix molecules that bind other integrins. Addition of echistatin, which is a soluble alpha(V)beta(3) ligand, significantly enhanced the hypotonic [Ca(2+)](i) increase in addition to inducing an immediate increase in [Ca(2+)](i) by itself. These results strongly support the contention that alpha(V)beta(3) integrin signaling in osteocytes interacts with that in mechanotransduction, which is downstream of SA-Cat.

Immortalization of cementoblast progenitor cells with Bmi-1 and TERT

A cementoblast progenitor cell line designated BCPb8 was successfully isolated from dental follicle cells immortalized with Bmi-1 and hTERT. BCPb8 showed the potential to differentiate into cementoblasts on implantation into immunodeficient mice. BCPb8 was confirmed to be the first established cementoblast progenitor cell line and will provide a useful model for investigating cementogenesis.

INTRODUCTION

The dental follicle is the mesenchymal tissue surrounding the developing tooth germ. During tooth root development, progenitor cells present in the dental follicle are believed to play a central role in the formation of periodontal components (cementum, periodontal ligament, and alveolar bone). However, little more is known about the biology of these progenitors. Previously, we observed that cultured bovine dental follicle cells (BDFCs) contained putative cementoblast progenitors. To further analyze the biology of these cells, we attempted to isolate cementoblast progenitors from immortalized BDFC through expression of the polycomb group protein, Bmi-1, and human telomerase reverse transcriptase (hTERT).

MATERIALS AND METHODS

BDFCs were transduced with replication-deficient retroviruses carrying human Bmi-1(LXSN-Bmi-1), and hTERT (LXSH-hTERT) for immortalization. Single cell clones were established from immortalized BDFC, and differentiation into cementoblasts was assessed by implantation into immunodeficient mice.

RESULTS AND CONCLUSION

BDFCs expressing Bmi-1 and hTERT showed an extended life span-90 population doublings more than normal BDFCs-and still contained cells with the potential to differentiate into cementoblasts on implantation into immunodeficient mice. From these cells, we established a clonal cell line, designated BCPb8, which formed cementum-like tissue that was reactive to the anti-cementum-specific monoclonal antibody 3G9 and expressed mRNA for bone sialoprotein, osteocalcin, osteopontin, and type I collagen on implantation. Thus, by using Bmi-1 and hTERT, we succeeded in immortalizing cementoblast progenitor cells from BDFC without affecting differentiation potential. The BCPb8 cell line is the first immortalized clonal cell line of cementoblast progenitors and could be a useful tool not only to study cementogenesis but also to develop regeneration therapy for patients with periodontitis.

Biomimetic approach on human periodontal ligament cells using synthetic oligopeptides

BACKGROUND

Periodontal ligament (PDL) cells, connecting root cementum with alveolar bone, are important for periodontal wound healing. In order to obtain a predictable periodontal regeneration, selective adhesion and proliferation of PDL cells are essential. The purpose of this study was to investigate the effects of synthetic peptides mimicking cell-binding domain of fibronectin (FN) on human PDL cells.

METHODS

Two types of oligopeptides, Gly3-Pro-His-Ser-Arg-Asn-Gly6-Arg-Gly-Asp-Gly (G3PHSRNG6RGDG) and Gly3-His-Pro-Asn-Arg-Ser-Gly6-Arg-Gly-Asp-Gly (G3HPNRSG6RGDG), were constructed using a solid-phase peptide synthesizer. Fibronectin type III ninth to tenth domain (FN III 9-10) and Arg-Gly-Asp-Ser (RGDS) were prepared for comparison with the effects of synthetic peptides. These peptides were coated onto 96-well cell culture plates with 0.001 approximately 100 microM concentrations. Cultured human PDL cells were then applied to the peptide-coated wells at a density of 1 x 10(4)/well. After 1 hour incubation at 37 degrees C, adhered cells were fixed, stained, and examined by phase contrast microscopy for cell spreading assay. Attached PDL cells were solubilized with 2% sodium dodecyl sulfate (SDS) for the cell attachment assay by measuring absorbance at 595 nm in microplate reader. Western blot analysis was performed to determine extracellular signal-regulated kinase (ERK1/2) activity.

RESULTS

Cell attachment and spreading assays revealed that G3PHSRNG6RGDG (> or = 10 microM) possesses similar adhesive behavior to FN III 9-10. G3PHSRNG6RGDG showed a comparable ERK1/2 activity when compared to FN III 9-10.

CONCLUSIONS

G3PHSRNG6RGDG enhanced an attachment and spreading of human PDL cells thereby increasing ERK1/2 activity. Taken together, it is anticipated that this peptide might be a potential tool for arranging a biologically attractive environment for PDL cells, which would enhance periodontal regeneration efficacy.

Role of Hertwig's epithelial root sheath cells in tooth root development

During tooth development, after the completion of crown formation, the apical mesenchyme forms the developing periodontium while the inner and outer enamel epithelia fuse below the level of the crown cervical margin to produce a bilayered epithelial sheath termed Hertwig's epithelial root sheath (HERS). The role of HERS cells in root formation is widely accepted; however, the precise function of these cells remains controversial. Functions suggested have ranged from structural (subdivide the dental ectomesenchymal tissues into dental papilla and dental follicle), regulators of timing of root development, inducers of mesenchymal cell differentiation into odontoblasts and cementoblasts, to cementoblast cell precursors. The characterization of the HERS phenotype has been hindered by the small amount of tissue present at a given time during root formation. In this study, we report the establishment of an immortal HERS-derived cell line that can be maintained in culture and then induced to differentiate in vitro. Characterization of the HERS phenotype using reverse transcriptase-polymerase chain reaction and Western blot immunostaining suggests that HERS cells initially synthesize and secrete some enamel-related proteins such as ameloblastin, and then these cells appear to change their morphology and produce a mineralized extracellular matrix resembling acellular cementum. These studies suggest that the acellular and cellular cementum are synthesized by two different types of cells, the first one by HERS-derived cementoblasts and the later by neural crest-derived cementoblasts.

Immunohistochemical localisation of extracellular matrix proteins in the periodontium during cementogenesis in the rat molar

OBJECTIVE

The development of the periodontium involves the coordinated expression of numerous extracellular matrix (ECM) macromolecules and their receptors (integrins). The aim of this study was to determine the expression of selected hard and soft tissue matrix molecules and the integrin alpha5beta1 in the periodontal tissues, during cementogenesis in the rat molar.

METHODS

Using immunohistochemical methods, the distribution of the extracellular matrix proteins, fibronectin, tenascin, and bone sialoprotein (BSP), as well as the integrin subunits alpha5 and beta1 were studied in rats aged 3, 5 and 8 weeks.

RESULTS

Fibronectin was widely distributed in the gingival epithelium, gingival connective tissue and in the periodontal ligament. Tenascin expression was less marked compared with fibronectin, but was more distinctly associated with cells and peri-cellular areas of the epithelial-connective tissue interface, the gingiva and within the periodontal ligament. The fibronectin-receptor alpha5beta1 integrins were expressed by epithelial cells, periodontal ligament cells and gingival fibroblasts. A notable finding was the increased staining intensity of fibronectin, tenascin and alpha5beta1 integrin in all 5-week old molar sections in the periodontal ligament matrix and cells, apical to the cemento-enamel junction (CEJ) along the alveolar crest (AC) ridge height. Bone sialoprotein was distinctly associated with the hard tissues of the periodontium as acellular cementum and alveolar bone matrix expressed bone sialoprotein throughout all sections, in all age groups.

CONCLUSIONS

In conclusion, this study has demonstrated the selective distribution of several hard and soft tissue matrix molecules during periodontogenesis. The results highlight the complex nature of interactions of various proteins and molecules during development. The interactions between these molecules and their specific roles in development and regeneration await further investigation.

Effects of echistatin and an RGD peptide on orthodontic tooth movement

We tested whether orthodontic tooth movement (OTM) could be blocked by local administration of echistatin or an arginine-glycine-aspartic acid (RGD) peptide, agents known to perturb bone remodeling, adjacent to maxillary molars in rats. These molecules were incorporated into ethylene-vinyl acetate (ELVAX), a non-biodegradable, sustained-release polymer. In vitro experiments showed that the echistatin and RGD peptide were released from ELVAX in active forms at levels sufficient to disrupt osteoclasts. Biotinylated RGD peptide was released from ELVAX into the PDL after surgical implantation. ELVAX loaded with either RGD peptide or echistatin and surgically implanted next to the maxillary molars inhibited orthodontic tooth movement (p < 0.01). The RGD peptide also reduced molar drift (p < 0.05). This study shows the feasibility of using ELVAX to deliver integrin inhibitors adjacent to teeth to limit local tooth movement in response to orthodontic forces.

Cementum and periodontal wound healing and regeneration

The extracellular matrix (ECM) of cementum resembles other mineralized tissues in composition; however, its physiology is unique, and it contains molecules that have not been detected in other tissues. Cementum components influence the activities of periodontal cells, and they manifest selectivity toward some periodontal cell types over others. In light of emerging evidence that the ECM determines how cells respond to environmental stimuli, we hypothesize that the local environment of the cementum matrix plays a pivotal role in maintaining the homeostasis of cementum under healthy conditions. The structural integrity and biochemical composition of the cementum matrix are severely compromised in periodontal disease, and the provisional matrix generated during periodontal healing is different from that of cementum. We propose that, for new cementum and attachment formation during periodontal regeneration, the local environment must be conducive for the recruitment and function of cementum-forming cells, and that the wound matrix is favorable for repair rather than regeneration. How cementum components may regulate and participate in cementum regeneration, possible new regenerative therapies using these principles, and models of cementoblastic cells are discussed.

Expression of integrins by human periodontal ligament and gingival fibroblasts and their involvement in fibroblast adhesion to enamel matrix-derived proteins

We showed recently that human periodontal ligament (PDL) and gingival fibroblasts adhere and spread on enamel matrix protein (EMP) coatings. In the present study, we investigated whether this interaction can be attributed to integrin expression. Human PDL and gingival fibroblasts were cultured for periods up to 24 h on EMP coatings, in the presence of synthetic RGD-containing peptide or an antibody against the beta1 integrin subunit. The cells were first cultured for 24 h under serum-free conditions and then cultured on EMP coatings for 48 h. Integrin expression levels were assessed by flow cytometry analysis. It was found that attachment and spreading on EMP was inhibited by the synthetic RGD-containing peptide, but not by a synthetic RGE-peptide. Both PDL and gingival fibroblasts showed expression of the integrin subunits, alpha2, alpha5, beta1, and the integrin, alphavbeta3. Incubation with an antibody against the beta1 subunit significantly inhibited the attachment and spreading of PDL and gingival fibroblasts on EMP coatings. We conclude that integrins are involved in the interaction of PDL and gingival fibroblasts with EMP.

Attachment of human periodontal ligament cells to enamel matrix-derived protein is mediated via interaction between BSP-like molecules and integrin alpha(v)beta3

BACKGROUND

Although enamel matrix-derived protein (EMD) can stimulate attachment of human periodontal ligament (HPDL) cells to the root surface, the biological mechanism of this phenomenon is unclear. The purpose of this study was to determine which molecules in EMD are involved in the attachment of HPDL cells, and which types of integrins on the cell surface mediate the interaction between the cells and EMD.

METHODS

HPDL explants were obtained from tooth surfaces extracted from 4 individuals, and cells taken from the individual explants were separately harvested and subcultured through as many as 5 passages. Cells were incubated on EMD-coated culture plates with and without neutral antibodies for integrins or RGD-sequence blocking peptides and stained with toluidine blue. Proteins in EMD that were able to induce cell attachment were identified by incubating sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) replicas with HPDL cells; the cell-binding regions were detected by staining the cells with toluidine blue. Characteristics of the cell-binding proteins in the EMD were identified by Western blot analysis.

RESULTS

It was shown that anti-alpha(v)beta3 antibody and GRGDSP peptide markedly reduced attachment of HPDL cells to EMD. When the cells were incubated with SDS-PAGE replicas, distinct cell attachment was observed at a molecular mass of approximately 55 kDa. The cell-binding ability of this protein was completely blocked by treatment with anti-alpha(v)beta3 antibody or GRGDSP peptide. In the Western blot analysis, the 55 kDa protein was recognized by anti-bone sialoprotein (BSP) antibody as a single band.

CONCLUSIONS

Our study provides the first evidence that the attachment of HPDL cells to EMD can be mediated by interaction between a BSP-like molecule and integrin alpha(v)beta3 on the cell surface.

Extracellular matrix molecules improve periodontal ligament cell adhesion to anorganic bone matrix

Bone replacement graft (BRG) materials are used in periodontal therapy to encourage new bone formation. Extracellular matrix proteins may improve periodontal ligament fibroblast (PDLF) attachment to these materials. We demonstrate that PDLFs adhere well to the extracellular matrix (ECM) proteins fibronectin, vitronectin, laminin, and collagen types I and IV. PDLFs express numerous ECM-receptor integrin subunit transcripts (alpha1, alpha2, alpha3, alpha4, alpha5, alpha11, beta1, beta5, and beta8) at high levels, while others (alpha6, alpha9, alphaV, beta3, beta6, and beta7) are expressed at reduced levels. Despite the fact that PDLFs adhere well to fibronectin and collagen type IV bound to plastic, and express integrins that recognize these ECM proteins, they do not attach well to anorganic bovine bone matrix (ABM) coated with these same proteins. However, the addition of vitronectin, laminin, or collagen type I to these same ABMs substantially increased PDL cell attachment. Thus, selective use of ECM proteins may be clinically useful in promoting cell attachment to ABM and bone regrowth.

Gingival, dermal, and periodontal ligament fibroblasts express different extracellular matrix receptors

BACKGROUND

Fibroblasts are the predominant cells of the periodontal ligament and the gingiva and have important roles in the function and regeneration of the tooth support apparatus. The goal of this study was to investigate the possible differences in the adhesion properties and expression of extracellular matrix (ECM) receptors among different fibroblast populations.

METHODS

The adhesion of gingival (GF), dermal (DF), and periodontal ligament fibroblast (PDLF) cultures to ECM proteins (fibronectin, laminin, vitronectin, RGD peptide, collagen type I, and collagen type IV) adsorbed to tissue culture plastic was evaluated fluorometrically. Quantitative reverse transcription-polymerase chain reactions (RT-PCR) were performed using primers specific for 19 integrin subunits to quantify ECM receptor transcript expression.

RESULTS

Our data demonstrated that GF and PDLF adhere to vitronectin and collagen types I and IV more avidly than do DF. PDLF adhered well to laminin, whereas GF and DF did not. Quantitation of integrin expression demonstrated that the different fibroblast types expressed different integrin transcripts, further demonstrating their innate differences.

CONCLUSIONS

The 3 fibroblast types studied behave differently and expressed different ECM receptors. However, gingival fibroblasts and periodontal ligament fibroblasts are more similar in their attachment and integrin expression than either is to dermal fibroblasts. Therefore, experiments using DF will not necessarily be valid for oral tissues.

Effect of nicotine on fibroblast beta 1 integrin expression and distribution in vitro

BACKGROUND

Integrins are a family of transmembrane cell surface glycoproteins, and those with the beta 1-subunit function in both cell-to-cell and cell-to-substrate adhesion. The purpose of this study was to determine nicotine's effect on the expression and distribution of the beta 1 integrin subunit on the human gingival fibroblast cell surface.

METHODS

Pure nicotine was diluted in medium to the following concentrations: 0 (control), 0.025, 0.05, 0.1, 0.2, and 0.4 microM. Human gingival fibroblasts (HFG) were grown for 24 hours in each concentration and fluorescein-labeled with a mouse monoclonal anti-human beta 1 antibody and secondarily incubated with a urease-labeled anti-mouse IgG antibody. After a final wash, the cells were incubated with urea/bromcresol blue substrate for 15 minutes at 37 degrees C and measured in a microplate reader at 570 nm.

RESULTS

The integrin beta 1-subunit was detected on the HGF surface membrane by fluorescence labeling, and cell-enzyme-linked immunosorbent assay testing demonstrated its decreased expression with increasing nicotine concentrations that were statistically different at the concentrations of 0.2 and 0.4 microM versus controls (P < 0.05).

CONCLUSIONS

Nicotine concentrations of 0.2 and 0.4 microM significantly decrease beta 1 integrin expression in human gingival fibroblasts that may affect cell-cell and cell-substratum adhesion during wound healing.

Extracellular matrix cell adhesion peptides: functional applications in orthopedic materials

This review describes research on selected peptide sequences that affect cell adhesion as it applies in orthopedic applications. Of particular interest are the integrin-binding RGD peptides and heparin-binding peptides. The influence of these peptides on cell adhesion is described. Cell adhesion is defined as a sequence of four steps: cell attachment, cell spreading, organization of an actin cytoskeleton, and formation of focal adhesions. RGD sequences clearly influence cell attachment and spreading, whereas heparin-binding sequences appear to be less efficient. Collectively, these sequences appear to promote all steps of cell adhesion in certain cell types. This review also addresses issues related to peptide immobilization, as well as potential complexities that may develop as a result of using these versatile cell-binding sequences. Also described are future directions in the field concerning use of existing and more sophisticated peptide substrata.

Enamel matrix-derived protein stimulates attachment of periodontal ligament fibroblasts and enhances alkaline phosphatase activity and transforming growth factor beta1 release of periodontal ligament and gingival fibroblasts

BACKGROUND

Although it is claimed that enamel matrix-derived proteins (EMP) can be used to promote new attachment formation around periodontally involved teeth, the underlying biological mechanism is not understood. It was the aim of the present study to investigate the effects of EMP on the behavior of human periodontal ligament (HPLF) and gingival fibroblasts (HGF) in vitro, with special focus on their attachment properties, the expression of alkaline phosphatase (ALP) activity, the release of transforming growth factor (TGF)beta1, and their proliferative rate.

METHODS

Fibroblast populations were obtained from 10 individuals with a healthy periodontium and cultured in chemically defined medium on culture plates coated with EMP, purified collagen type I, or their respective vehicles. Experiments were performed in the absence of serum for periods up to 48 hours.

RESULTS

It was shown that HGF barely attached and spread on EMP-coated substrata, whereas HPLF attached and spread within 24 hours. However, when cultured on purified collagen type I, both cell types showed rapid attachment and spreading. Furthermore, the expression of ALP activity was significantly enhanced under the influence of EMP, especially in HPLF. HPLF and HGF both released significantly higher levels of TGFbeta1 in the presence of EMP. EMP did not influence 3H-thymidine incorporation by HPLF and HGF.

CONCLUSIONS

Our results indicate that HPLF and HGF respond differently to EMP. A more rapid attachment of HPLF to this substratum might contribute, during the initial stages of periodontal healing, to selective outgrowth and colonization of exposed root surfaces in vivo.

Role of interactions between integrins and extracellular matrix components in healthy epithelial tissue and establishment of a long junctional epithelium during periodontal wound healing: a review

Following the surgical treatment of adult periodontitis, the epithelial regeneration of the periodontal attachment is non-physiological and thus unsatisfactory, if membranes or artificial bone material are not used. Re-epithelialization is based on the proliferation, migration, and differentiation of basal epithelial cells which are in contact with a wound matrix and whose molecular makeup differs from the extracellular matrix of intact regions. Interactions between basal epithelial cells and the extracellular matrix are mediated by special receptors on the cell surface which are known as integrins and belong to the family of cellular adhesion molecules (CAM). Various studies indicate that integrin-mediated interaction plays a decisive role in regulating the proliferation, migration, and differentiation of the epithelial cells. This review provides an overview of the in vivo and in vitro expression of integrins by epithelial cells and the interaction between integrins and extracellular matrix (ECM) in the case of a stationary epithelium and during wound healing. The regulation of these cell-cell and cell-matrix interactions may represent a method for inhibiting non-physiological epithelial regeneration on the molecular level.

Isoform-specific attachment of osteoprogenitors to laminins: mapping to the short arms of laminin-1

The recruitment of osteoblast progenitors involves their migration and attachment to the sites of bone formation through interactions with matrix proteins. In a time-limited cell attachment assay, coated laminin-1 inhibits the adhesion of most rat calvaria cells but attaches specifically to osteoprogenitors, as quantified by the number of bone colonies (nodules) formed in the cultures. In order to determine the molecular mechanisms involved in osteoprogenitor attachment to laminin-1, we investigated the effects of laminin-5, a N-truncated laminin variant. In contrast to laminin-1, laminin-5 increased (1.5-fold) rat calvaria cell attachment and did not display any specific affinity for osteoprogenitors. In competition experiments on laminin-5, blocking antibodies directed against either the integrin chain beta1 or the C-terminal portion of laminin-5, as well as thermic denaturation of the protein at 80 degrees C, inhibited rat calvaria cell attachment, suggesting the implication of integrin alpha3beta1 binding to the conformation-dependent C-terminal end of laminin-5. Stepwise thermic denaturation did not suppress the anti-adhesive activity of laminin-1, while osteoprogenitor recruitment was abolished after denaturation above 60 degrees C, suggesting that different domains are involved in these two effects. The anti-beta1 antibody further decreased RC cell attachment to laminin-1, providing evidence for concomitant anti-adhesive and beta1-dependent cell attachment activities. Blocking of beta1 integrin subunit did not, however, reduce osteoprogenitor recruitment. Finally, purified elastase digestion fragment E1+, encompassing the N-terminal short arms of laminin-1, reproduced the effects of the complete molecule in the assay, while C-terminal fragment E8 did not display any cell attachment or osteoprogenitor recruitment properties. In conclusion, the anti-adhesive and osteoprogenitor-selective effects of laminin-1 on rat calvaria cell populations are distinct, beta1-integrin-independent properties mapping to the short arms of the molecule and thus not displayed by the truncated laminin-5.

Monoclonal antibodies against integrin subunits alpha6 and beta1 inhibit migration of gingival epithelium in organ culture

BACKGROUND

The main problem in the posterior instrumental treatment of periodontitis is the re-epithelization of the periodontal defects, leading to the formation of an unphysiological, long junctional epithelium inhibiting the regeneration of periodontal attachment. A precondition for the re-epithelization is the interaction between epithelial cells and their extracellular matrix mediated by integrins. Integrins are cellular adhesion molecules (CAM), binding to different structures of the extracellular matrix, e.g., collagen, laminin, or fibronectin.

METHODS

Biopsy specimens of marginal gingiva, composed of epithelium and subepithelial connective tissue, were cultivated on microporous membranes in tissue culture plates. The culture medium was supplemented with monoclonal antibodies directed against human integrin subunits. The period of cultivation was 6 days and the medium was replaced daily. After cultivation, the tissue development was analyzed by histological and immunohistochemical methods.

RESULTS

We found that the combination of antibodies directed against the integrin subunits alpha6 and beta1 inhibited the migration of epithelium completely in 9 out of 10 cultures, whereas control cultures containing none or only irrelevant antibodies demonstrated connective tissues completely covered by epithelium.

CONCLUSIONS

Influencing the regeneration of periodontal tissue on a molecular basis by using antibodies directed against integrin subunits may be of future interest in postsurgical treatment of periodontal diseases.

TGF-beta1 influences early gingival wound healing in rats: an immunohistochemical evaluation of stromal remodelling by extracellular matrix molecules and PCNA

The effect of topically applied transforming growth factor beta1 (TGF-beta1) on the rat gingival wound healing process after flap surgery was evaluated by immunohistochemistry for extracellular matrix molecules (ECM), such as tenascin, heparan sulfate proteoglycan (HSPG) and type IV collagen, and for proliferating cell nuclear antigen (PCNA) in fibroblasts. TGF-beta1 solution was applied to the surgical wound experimental sites. Two microg/microl were applied at the time of the operation, and 1 microg/microl at days 1 and 2 after surgery, with contralateral control sites receiving the vehicle alone. Periodontal tissues were histologically examined at 3 and 7 days post-surgery. Tenascin was found to be more strongly stained in the granulation tissue from experimental sites at 3 days post-surgery. At 7 days postsurgery, HSPG-positive areas in granulation tissue had become smaller and there was a prominent proliferation of PCNA-positive fibroblast-like cells and type IV collagen-positive blood vessels. These results suggest that TGF-beta1 applied to surgical wounds influences early proliferation of gingival fibroblast-like cells, the formation of blood vessels, and ECM remodelling. In conclusion, TGF-beta1 application appears to promote granulation tissue formation in periodontal wound healing.

The response of periodontal ligament cells to fibronectin

Fibronectin (fn) is an extracellular matrix (ECM) molecule important in cell adhesion and migration and in wound healing. It is also likely important in periodontal ligament (PDL) cell-ECM interactions, and thus in regenerating periodontal tissues. In this study we characterized PDL cells and their interactions with FN, testing different PDL cell isolates taken from healthy and diseased conditions. PDL cells were characterized by their morphology, integrin profile, motility, and bone nodule formation. Cells were then assayed for adhesion, proliferation, and chemotaxis in response to FN or FN fragments. Cell isolates were morphologically heterogeneous and fibroblastic, had a normal-appearing actin cytoskeleton and a wide range of migration potentials, and formed bone-like nodules in vitro. They expressed alpha5, beta1, alpha v, and alpha4 integrin subunits, known receptors for FN, and in fact they bound FN preferentially at 5 and 10 microg/ml. Intact FN induced greater PDL cell proliferation and chemotaxis than did FN fragments (120-kDa cell-binding, 60-kDa heparin-binding, and 45-kDa collagen-binding). PDL cells harvested from diseased and healthy conditions were no different on the basis of these assays. These data demonstrate that PDL cells are a mixed population of fibroblastic cells, capable of forming a mineralized matrix. They also suggest that maximal proliferation and chemotaxis require specific FN domains that are present on the intact molecule but not its fragments.

Synthetic integrin-binding peptides promote adhesion and proliferation of human periodontal ligament cells in vitro

Periodontal ligament (PDL) cells have been shown to express several integrins (alphav, alpha5, beta1, beta3) that use RGD (arginine-glycine-aspartic Acid)-dependent mechanisms for the recognition and binding of their ligands. The objective of this study was to evaluate the effects of certain integrin-binding cyclic and linear synthetic RGD-containing peptides on PDL cells' adhesion, proliferation, and de novo protein synthesis in vitro. Fifth passages of normal human PDL cells established from teeth extracted from patients (ages 12 to 14) for orthodontic reasons were used for all experiments. Synthetic peptides containing the EPRGDNYR sequence in two different spatial conformations (linear and cyclic) were covalently attached to bovine serum albumin (BSA). Type I collagen, EPRGDNYR-BSA conjugates, 1:1 mixtures of type I collagen and conjugates, as well as BSA (a negative control) were coated on bacteriological plastic and evaluated for their attachment-promoting activities. In addition, the effects of these substrates on cell proliferation were evaluated by [3H]thymidine incorporation by the PDL cells. For attachment and spreading, the cyclic forms of EPRGDNYR-BSA conjugate and type I collagen were most potent, followed by linear EPRGDNYR-BSA conjugate. The effects of all collagen/conjugate mixtures were equivalent to that of type I collagen except for the collagen/linear EPRGDNYR-BSA mixture, which was less potent. The cyclic EPRGDNYR-BSA conjugate was the most effective substrate to stimulate cell proliferation, and it was followed in potency by the linear peptide-BSA conjugate. Collagen alone did not stimulate [3H]thymidine incorporation above the control level. Mixtures of collagen with all of the conjugates showed stimulatory effects similar to that of the cyclic peptide-BSA conjugate. No significant differences in de novo protein synthesis were detected. These results suggest that the synthetic RGD-containing peptides attached to a carrier are potent ligands for the human PDL cells, and that they could provide a basis for the development of new strategies aimed at the regeneration of the periodontium.

Flow cytometry analysis of gingival and periodontal ligament cells

Gingival and periodontal ligament (PDL) fibroblasts are the major cellular components of periodontal soft connective tissues, but the precise differences between these cells are not yet known. In the present study, we have therefore examined the phenotypic and functional features of the cells obtained from gingival and PDL biopsy samples. Spindle-shaped cells characteristic of fibroblasts were the main cell type observed in vitro, although epithelial cells were also present in primary gingival cell cultures. Flow cytometry was used to measure the size and granularity of the cultured cells, and showed that the gingival fibroblasts were smaller and less granular compared with the PDL cells. The expression of certain key extracellular matrix (ECM) proteins, fibronectin, collagen type I, and tenascin was measured by flow cytometry. Analysis of the fluorescence profiles of these cultures showed that the majority of cells expressed fibronectin and that the average fluorescence intensity of this antigen in the PDL cells was higher than that in the gingival fibroblasts. Moreover, the fibronectin-positive PDL cells apparently comprised two subpopulations which expressed fibronectin at different levels, suggesting that the cells in the PDL cultures were functionally heterogeneous. The level of collagen type I was also found to be up-regulated in the PDL compared with the gingival cells and, as with fibronectin, was expressed at two different levels by subsets of the PDL cells. In contrast, tenascin was expressed at very similar levels by both the gingival fibroblasts and PDL cells. In addition, measurement of alkaline phosphatase, a marker enzyme for mineralized tissue-forming cells, showed that the PDL cells had higher activity than the gingival fibroblasts and that the alkaline phosphatase activity in the PDL cells was far more markedly up-regulated by dexamethasone. Our findings demonstrate that, despite their similar spindle-shaped appearance, fibroblasts derived from gingival and PDL tissues appear to display distinct functional activities which are likely to play a vital part in the maintenance of tissue integrity and regenerative processes.

Leukocyte adhesion molecules

Recruitment of leukocytes is critical to many of the processes studied in oral biology. With the development of new tools such as monoclonal antibody production and transgenic mice, the specific adhesion molecules thought to be important in leukocyte recruitment have been identified and their function examined. These molecules can be divided into three major classes: selectins, members of the immunoglobulin superfamily, and integrins. They mediate interactions between leukocytes and endothelial cells, facilitating the initial process of leukocyte rolling, firm attachment to endothelium, transendothelial migration, diapedesis, and migration along connective tissue. The goal of this paper is to provide an understanding of which molecules are involved in the above processes by discussing their cellular distribution, counter-receptors, and physiologic function.

Laminin binding to a heat-modifiable outer membrane protein of Actinobacillus actinomycetemcomitans

The interaction of Actinoabacillus actinomycetemcomitans with the basement membrane protein, laminin, was examined in a 125I-labeled protein-binding assay. The binding of laminin increased by lowering the pH. The ability to bind laminin was decreased in cells at the stationary phase of growth and by the presence of blood in the culture medium. Laminin binding to this bacterium was saturable, and the affinity constant was 4.6 nM. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blot (ligand blot) analysis of cell-envelope and outer membrane of A. actinomycetemcomitans displayed a 125I-laminin-reactive protein band with a molecular weight of 29 k. The laminin-binding protein was the previously described outer membrane protein A of A. actinomycetemcomitans. It was identified by its heat-modifiable property, detergent-solubility profile and reactivity with outer membrane protein A-specific polyclonal antiserum. At acidic pH, 25I laminin bound to several cell-envelope components of A. actinomycetemcomitans, but at neutral pH, laminin bound only to the heat-modifiable protein. Despite the existence of the laminin-binding protein, cells grown in blood-containing media did not bind laminin. Several mammalian proteins interfered with laminin-bacterial interaction, including lactoferrin, which binds to the same bacterial protein that inhibited and displaced the laminin-bacterial interaction.

Immunohistochemical localization of very late activation integrins in healthy and diseased human gingiva

The beta 1-integrins (VLA family) are cellular adhesion molecules (CAM) that play a major role in cell-cell and cell-matrix interactions. The expression pattern of CAM was studied in 5 clinically normal volunteers with healthy gingiva and in 18 patients with clinically different stages of periodontitis. In healthy human gingiva alpha 2, alpha 3 and alpha 6 integrin chains were found in a characteristic distribution, showing a broad continuous expression on the junctional and sulcular epithelium sites. The expression of these integrins was demonstrated primarily on the basal cell layers and in some cells of the stratum spinosum. Inflammatory stages of periodontitis revealed further upregulation of alpha 2, alpha 3 and alpha 6 integrins into the junctional and sulcular epithelial cells, which correlated with the stage of the periodontitis and the extent of the cellular infiltration. alpha 4 and alpha 6 were found to be the predominant beta 1 integrin chains on inflammatory cells. The amount of alpha 4 and alpha 6 positive infiltrative cells increased with the number of inflammatory cells. VCAM-1, the corresponding cell-cell ligand of VLA-4 (alpha 4) was present on the majority of subepithelial vessels in all stages of gingivitis and periodontitis. The alpha 5 subunit was expressed on both endothelium and gingival connective tissue cells. Samples from advanced periodontitis cases showed a higher number of alpha 5 positive mononuclear cells. In comparison to normal epidermis, human gingival epithelial cells express higher levels of integrins. This expression is further upregulated in advanced stages of periodontitis, indicating changes of the beta 1 integrin organization.

Turnover in periodontal connective tissues: dynamic homeostasis of cells, collagen and ground substances

The connective tissues of the periodontium are composed of two soft tissues and two hard tissues--each of which has unique features. This review considers the constituents of normal, healthy periodontal connective tissues together with an appraisal of the changes in the connective tissue matrices of the periodontium which occur during the development of periodontitis. Recent developments in this field have paved the way for new and exciting vistas in periodontal diagnosis and regeneration which, ultimately, are two important goals in periodontal therapy.

ICAM-1-expressing pocket epithelium, LFA-1-expressing T cells in gingival tissue and gingival crevicular fluid as features characterizing inflammatory cell invasion and exudation in adult periodontitis

Activated T lymphocytes constitute a major component of inflammatory cells in the early periodontal lesion, and also appear in the gingival crevicular fluid. In an attempt to clarify the relationship between the ICAM-1 (CD54) expression of pocket epithelium in gingiva and the infiltrating lymphocyte population, we carried out an analysis of CD11a+(LFA-1 alpha), CD25+(IL-2R alpha) and CD4+(Th) cells subjacent to ICAM-1-expressing pocket epithelia and CD11a+CD25+CD4+ cells in gingival crevicular fluid (GCF). GCF was collected by crevicular washing from 16 patients with periodontitis (P group) and 3 subjects with healthy gingiva (H group). Peripheral blood (PB) was collected at the same time. Mononuclear cells were isolated by Ficoll-paque gradient centrifugation from GCF and PB. Monoclonal antibodies (mAb) to CD11a, CD25, and CD4 were used for three-color flow cytometry. Gingival biopsies were obtained from 7 patients in P group and 3 subjects in H group. Serial cryostat sections (6 microns in thickness) were prepared from each biopsy, on which a double staining was performed. The number of CD11a+CD25+CD4+ cells and the fluorescence intensity of FITC conjugated anti-CD11a were significantly higher in GCF than in PB (p < 0.001 to p < 0.01). CD11a+CD25+CD4+ cells were not detected in GCF in H group. The pocket epithelia expressed CD54 in P group, but not in H group. The number of CD11a+, CD25+ and CD4+ cells infiltrating the connective tissue subjacent to the upper, middle and lower parts of the CD54 positive pocket epithelium (n = 16) was 141 +/- 26, 38 +/- 13, 144 +/- 29 (cells/0.04 mm2), respectively, whereas in the CD54 negative pocket epithelium, it was (n = 5) 9 +/- 2, 3 +/- 1, 8 +/- 3. In P group, the CD11a+CD25+CD4+ cell number in GCF correlated with CD25+, CD11a+ cells in the connective tissue subjacent to the CD54+ pocket epithelium. These results indicate that expression of ICAM-1 in pocket epithelium is relevant to the migration of CD11a, CD25, CD4 positive cells in connective tissue subjacent to the pocket epithelium into the periodontal pocket. Assessing the relationship of our findings and other adhesion molecules would offer important clues to the understanding of T cell migration in affected gingiva.

Immunohistochemical expression of extracellular matrix components of normal and healing periodontal tissues in the beagle dog

Periodontal regeneration requires formation of periodontal tissues lost due to periodontal disease. To better understand the formation of new periodontal tissues during periodontal repair and regeneration, immunohistochemical expression of extracellular matrix components of normal as well as healing periodontal tissues was evaluated and compared using the avidin-biotin complex immunohistochemical technique. For this purpose, horizontal furcation defects were created around mandibular P2 and P4 of 6 dogs after extraction of P1 and P3. The root surfaces were conditioned with citric acid and expanded polytetrafluoroethylene (ePTFE) membranes were placed and retained 0.5 mm above the cemento-enamel junction. The mucoperiosteal flaps were sutured in a coronal position. Two animals were sacrificed at 2, 4, and 8 weeks, and mesio-distal tissue slices containing normal or healing periodontal tissues were demineralized, dehydrated, and embedded in paraffin. Immunohistochemical localization of type I collagen (CI), fibronectin (FN), secreted protein, acidic and rich in cysteine (SPARC), vitronectin (VN), and bone sialoprotein (BSP) was performed on 6 microns thick sections. Morphological results demonstrated that at 2 weeks after defect creation, lesions were filled primarily with granulation tissue which was gradually replaced by newly-formed fibrous connective tissue, periodontal ligament (PDL), cementum, and bone between 4 and 8 weeks. The results of immunohistochemical study revealed that at 2 weeks the granulation tissue, especially in the intercellular spaces of inflammatory cells, was intensively stained for FN and VN. At 4 and 8 weeks, staining for CI, FN, and VN was found in fibrous connective tissue, the newly-formed PDL, cementum, and osteoid. Further the attachment zone of the PDL collagen fibers to cementum showed intense staining for FN. Immunostaining for SPARC was positive in the new PDL, cementum, and bone, while staining for BSP was restricted to the new cementum and bone. Interestingly, the PDL, especially in areas adjacent to active bone formation, demonstrated intense staining for BSP. However, fibrous connective tissue and PDL proper were unstained for BSP. These results indicate that FN and VN are involved in the early stages of periodontal repair, and periodontal regeneration is achieved through formation of periodontal tissues that are composed of different matrix components specific to different types of periodontal tissues.

The immunopathology of chronic inflammatory periodontal disease

Chronic inflammatory periodontal disease is known to be under the control of the immune response. However, the precise mechanism of the immunopathogenesis of this lesion has not yet been fully elucidated. In this review, the regulatory role of both lymphoid and non-lymphoid cells as well as cytokines and accessory molecules in the course of chronic inflammatory periodontal disease is discussed. Finally, based upon previous evidences, an attempt to establish a model of chronic inflammatory periodontal disease is made herein.

Osteopontin adhesion receptors on gingival fibroblasts

Osteopontin (OPN) promotes attachment and spreading of cells in an RGD dependent fashion, suggesting that OPN interacts with integrins on cell surfaces. Here in, we show that LM-609, a monoclonal antibody to the alpha v beta 3 integrin (a vitronectin receptor), inhibited OPN-mediated attachment of gingival fibroblasts. To characterize the cell surface receptors responsible for this interaction, we performed OPN-sepharose affinity chromatography using detergent extracts of 35S-methionine or 125I-surface labeled gingival fibroblasts. Proteins bound to the OPN-matrix were eluted with EDTA and subjected to SDS-PAGE under reducing conditions. EDTA eluates from both 125I-surface labeled and 35S-methionine labeled extracts demonstrated prominent bands in the 90kDa and 50kDa regions, by both autoradiography and fluorography, respectively. These studies suggest that OPN is associated with other cell surface molecules in addition to alpha v beta 3. Furthermore, these as yet to be characterized proteins, may prove to have a stronger affinity for OPN than alpha v beta 3.