Bacterial endotoxin inhibits migration, attachment, and orientation of human gingival fibroblasts in vitro and delays collagen gel contraction

Enhancing attachment of human gingival fibroblasts to periodontally compromised teeth: A comparative analysis of hyaluronic acid, EDTA, enamel matrix derivatives

Background

Gingival recession is a characteristic indicator of periodontitis and one of the factors that contributes to increased tooth clinical crown length. Patients with root exposure frequently undergo periodontal surgical procedures in addition to adjunctive therapy to increase root coverage area and soft tissue stability.

Purpose

This study aimed to evaluate fibroblast-root surface adhesion and determine whether periodontitis-damaged root surface microstructure can be restored using ethylenediaminetetraacetic acid (EDTA) and an enamel matrix derivative (EMD), individually or in combination.

Material and methods

Teeth extracted from patients with periodontal disease were used to create 60 samples, with each group containing six specimens. The test groups were provided root planing or root condition-specific materials (hyaluronic acid [HA], 24% EDTA, EMD, or EDTA/EMD) for varying treatment time periods. In contrast, the control group did not undergo any surface modifications. The samples and fibroblast cells were incubated for 72 h. The number of living cells on the root surface in each group was calculated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay (cell viability assessment).

Results

The control, root planing, and EMD groups showed that the root surfaces treated with EDTA for 4 min had significantly better cell adhesion. Surface EDTA treatment for 2 min significantly promoted cell attachment compared to root planing treatment. The root surfaces modified with EDTA/EMD for 2 and 4 min showed significantly improved cellular migration and adhesion compared to the root surface treated with root planing.

Conclusion

EDTA and EDTA/EMD substantially affected the root surface, which was related to the length of the treatment process. This effect shifts the surface properties, alters fibroblast interactions with the root surface, and recruits more cells to cover a larger area.

Current perspectives of residual ridge resorption: Pathological activation of oral barrier osteoclasts

PURPOSE

Tooth extraction is a last resort treatment for resolving pathological complications of dentition induced by infection and injury. Although the extraction wound generally heals uneventfully, resulting in the formation of an edentulous residual ridge, some patients experience long-term and severe residual ridge reduction. The objective of this review was to provide a contemporary understanding of the molecular and cellular mechanisms that may potentially cause edentulous jawbone resorption.

STUDY SELECTION

Clinical, in vivo, and in vitro studies related to the characterization of and cellular and molecular mechanisms leading to residual ridge resorption.

RESULTS

The alveolar processes of the maxillary and mandibular bones uniquely juxtapose the gingival tissue. The gingival oral mucosa is an active barrier tissue that maintains homeostasis of the internal organs through its unique barrier immunity. Tooth extraction not only generates a bony socket but also injures oral barrier tissue. In response to wounding, the alveolar bone socket initiates regeneration and remodeling through coupled bone formation and osteoclastic resorption. Osteoclasts are also found on the external surface of the alveolar bone, interfacing the oral barrier tissue. Osteoclasts in the oral barrier region are not coupled with osteoblastic bone formation and often remain active long after the completion of wound healing, leading to a net decrease in the alveolar bone structure.

CONCLUSIONS

The novel concept of oral barrier osteoclasts may provide important clues for future clinical strategies to maintain residual ridges for successful prosthodontic and restorative therapies.

Implications of endotoxins in wound healing: a narrative review

Bacterial toxins are thought to play a role in delayed wound healing in critically colonised and infected wounds. Endotoxins are released from Gram-negative bacteria when they are lysed by host phagocytic cells during an immune response, or by antimicrobial agents, potentially leading to a detrimental effect on the host tissues. Endotoxins can affect all aspects of the wound healing process, leading to delayed healing and contributing to wound chronicity. Release of endotoxins by bacteria can also have serious systemic effects (for example, septic shock) that can lead to high levels of patient mortality. This review summarises the role and implications on wound healing of bacterial endotoxins, describing the impact of endotoxins on the various phases of the wound healing response. There is a paucity of in vivo/clinical evidence linking endotoxins attributed to a wound (via antibiotic treatment) or their release from infecting bacteria with parameters of delayed wound healing. Future work should investigate if this link is apparent and determine the mechanism(s) by which such detrimental effects occur, offering an opportunity to identify possible treatment pathways. This paper describes the phenomenon of antimicrobial-induced endotoxin release and summarises the use of wound dressings to reduce wound bioburden without inducing microbial death and subsequent release of endotoxins, thus limiting their detrimental effects.

A re-evaluation of scaling and root planing

BACKGROUND

Extensive reviews on the role of scaling and root planing (SRP) in the treatment of periodontitis have been previously published. This commentary will address the importance of subgingival calculus in the progression and treatment of periodontitis and addresses factors that make the execution of a "definitive" SRP a critical part of therapy.

METHODS

A search for articles, using keywords relevant to the subject , (e.g., periodontitis, dental scaling, root planing, dental calculus, biofilm, inflammation) was conducted using PubMed, Ovid Medline, Cochrane Reviews and the ADA Center for Evidence Based Dentistry data bases. Additionally, references cited in relevant articles were also considered.

RESULTS

Surfaces of subgingival calculus are covered with a biofilm of metabolically active bacteria. Periodontal inflammation is clearly related to the presence of calculus and biofilm. The primary goal of SRP is removal of subgingival calculus and biofilm deposits to create a biologically compatible root surface and reduce the inflammatory burden. Current evidence suggests that inflammation associated with periodontal infections affects both the immediate oral environment and the patient's systemic health.

CONCLUSION

SRP is still critical to the treatment of periodontitis. SRP involving deep probing depths (≥ 5 mm) and root surfaces with anatomical and surface irregularities, regardless of the type of instrumentation, requires time, exceptional skill and perseverance, and patient compliance with periodontal maintenance. Sites with persistent nonresponding probing depths and signs of inflammation following a definitive SRP, should be considered for surgical intervention.

Early root surface colonization by human periodontal ligament fibroblasts following treatment with different biomaterials

OBJECTIVES

The present in-vitro study examined the effects of different biomaterials on early root surface colonization by human periodontal ligament (PDL) fibroblasts using confocal-laser-scanning-microscopy (CLSM).

MATERIALS AND METHODS

Fifteen periodontally-diseased teeth were extracted, treated with scaling/root planing and longitudinally cut to obtain 30 root fragments. Fragments were treated either with 24% EDTA following application of enamel matrix derivative (EMD), 24% EDTA or EMD only, nanocrystalline hydroxyapatite (NHA) paste or oily calcium hydroxide suspension (OCHS) for 1 h each. The analogue untreated root specimens served as controls. Root fragments were incubated with human PDL fibroblasts and cellular proliferation and morphology were evaluated after 1, 3, 5 and 8 days using CLSM-visualization and image recognition software.

RESULTS

The rate of cellular proliferation was different among treatment modalities examined (p = 0.019). Except treatment with NHA paste all treatment modalities improved cellular proliferation on root surfaces at all different points of time compared with the control specimens. A significant difference between treatment modalities was observed between EMD and NHA paste (p = 0.008). No synergistic effect could be demonstrated comparing root surface conditioning with 24% EDTA and EMD application compared to 24% EDTA or EMD application only.

CONCLUSION

The present results suggest that initial root surface colonization by PDL fibroblasts may be enhanced by root surface conditioning with 24% EDTA and application of EMD, application of 24% EDTA or EMD alone and OCHS. The addition of 24% EDTA for root surface conditioning prior to EMD application provided no synergistic effects in terms of early root surface colonization by PDL fibroblasts.

Porphyromonas gingivalis lipopolysaccharide induces shedding of syndecan-1 expressed by gingival epithelial cells

Syndecans are constitutively shed from growing epithelial cells as the part of normal cell surface turnover. However, increased serum levels of the soluble syndecan ectodomain have been reported to occur during bacterial infections. The aim of this study was to evaluate the potential of lipopolysaccharide (LPS) from the periodontopathogen Porphyromonas gingivalis to induce the shedding of syndecan-1 expressed by human gingival epithelial cells. We showed that the syndecan-1 ectodomain is constitutively shed from the cell surface of human gingival epithelial cells. This constitutive shedding corresponding to the basal level of soluble syndecan-1 ectodomain was significantly increased when cells were stimulated with P. gingivalis LPS and reached a level comparable to that caused by phorbol myristic acid (PMA), an activator of protein kinase C (PKC) which is well known as a shedding agonist. The syndecan-1 shedding was paralleled by pro-inflammatory cytokine interleukin-1 beta (IL-1beta), IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) release. Indeed, secretion of IL-1beta and TNF-alpha increased following stimulation by P. gingivalis LPS and PMA, respectively. When recombinant forms of these proteins were added to the cell culture, they induced a concentration-dependent increase in syndecan-1 ectodomain shedding. A treatment with IL-1beta converting enzyme (ICE) specific inhibitor prevented IL-1beta secretion by epithelial cells stimulated by P. gingivalis LPS and decreased the levels of shed syndecan-1 ectodomain. We also observed that PMA and TNF-alpha stimulated matrix metalloproteinase-9 secretion, whereas IL-1beta and P. gingivalis LPS did not. Our results demonstrated that P. gingivalis LPS stimulated syndecan-1 shedding, a phenomenon that may be mediated in part by IL-1beta, leading to an activation of intracellular signaling pathways different from those involved in PMA stimulation.

Anaerobic cocci populating the deep tissues of chronic wounds impair cellular wound healing responses in vitro

BACKGROUND

Anaerobic cocci are estimated to be present in the deep tissues of over 50% of chronic skin wounds. While the part they play in the chronicity of these wounds is uninvestigated, anaerobic cocci have previously been shown to be involved in other chronic inflammatory human conditions.

METHODS

In this study the anaerobic microflora of the deep tissues of 18 patients with refractory chronic venous leg ulcers (mean age 80.3 years; mean duration > 24 months) was characterized using strict anaerobic culture conditions. The effect of the anaerobic organisms isolated from these tissues on extracellular matrix (ECM) proteolysis and cellular wound healing responses was studied using in vitro models.

RESULTS

Anaerobic organisms were present in the deep tissues of 14 of 18 wounds and were principally Peptostreptococcus spp. The effects of three Peptostreptococcus spp. isolated from these wounds (P. magnus, P. vaginalis and P. asaccharolyticus) on cellular wound healing responses were compared with those of two pathogenic organisms also isolated from these wounds (Pseudomonas aeruginosa and Citrobacter diversus). While the direct ECM proteolytic activity exhibited by the Peptostreptococcus spp. was limited, they did significantly inhibit both fibroblast and keratinocyte proliferation, but only at high concentrations. However, at lower concentrations peptostreptococcal supernatants profoundly inhibited keratinocyte wound repopulation and endothelial tubule formation. The magnitude of these effects varied between strains and they were distinct from those demonstrated by Pseudomonas aeruginosa and Citrobacter diversus.

CONCLUSIONS

These studies confirm the importance of anaerobic organisms in chronic wounds and demonstrate an indirect, strain-specific mechanism by which these microorganisms may play a part in mediating the chronicity of these wounds.

The effect of bacterial endotoxin on the early tensile strength of healing surgical wounds

Wound healing in the oral cavity occurs in a bacteria-rich environment, which may affect its outcome. Furthermore, it takes place where forces are frequently applied to the healing tissue. The effect of bacterial endotoxin on the development of tensile strength in healing wounds was studied using surgical skin wounds in rats as a model. Collagen membranes soaked with 0.01 microg of bacterial endotoxin were inserted into surgical skin wounds, and their effect was studied on days 6 and 10. Membranes with no endotoxin served as controls. Endotoxin inhibited the early development of tensile strength in 6 days, healing wounds by 38%, whereas the collagen membrane alone had no effect. Dexamethasone (0.5 mg/kg every 72 h) had a suppressive effect on the development of tensile strength in healing noncontaminated wounds, but not in those containing bacterial endotoxin. These results suggest that bacterial endotoxin may interfere with the early healing of wounds. Understanding the mechanisms of this inhibition may result in treatments that will allow this response to be faster and more reproducible.

Effects of irradiation of an erbium:YAG laser on root surfaces

The application of erbium:YAG laser (Er:YAG) irradiation has been investigated for periodontal therapy. The purpose of this study was to evaluate the effects of Er:YAG laser irradiation on root surfaces using a scanning electron microscope (SEM) and to determine the laser's ability to remove lipopolysaccharides (LPS). Infrared spectrophotometry was used to investigate the effects of the laser on LPS applied to root dentin pellets. Premolars extracted for orthodontic reasons were prepared for this study. The crowns were resected below the cemento-enamel junction, longitudinally sectioned, and the contents of the pulp chamber were removed. Then 15 root tips (5 x 5 x 1 mm) were classified into 3 groups of 5 each as follows: group 1, tips without any treatment; group 2, planed tips with the cement layers left untouched; and group 3, planed until the dentin surface was disclosed. The center of each specimen was used as the experimental irradiated area and the peripheral area served as a control. The quantity of vapor delivered by Er:YAG laser was highly increased, and the irradiated areas displayed little morphogenetic changes. The lyophilized sample LPS 0111 B4 from E. coli was then mixed with potassium bromide and pressed into a tablet, which was examined at 4,000-650 Kayser. The lyophilized LPS had a peak at 2.94 microns. LPS on the root dentin pellets was cleared away as much as possible by 150 washings in pyrogen-free water using an ultrasonic cleaner. Five microliters of 24 EU LPS solution was dropped on the root dentin pellets, which were then irradiated by the Er:YAG laser, and washed using the ultrasonic cleaner in pyrogen-free water. The amount of the extracted LPS solution was determined by spectrophotometer at 405 nm. The Er:YAG laser could remove 83.1% of the LPS. This study suggests that Er:YAG laser irradiation might be useful for root conditioning in periodontal therapy. However, clinical testing is necessary to establish what, if any, utility the Er:YAG laser has as a part of periodontal therapy.

A comparison of the ability of intra-oral and extra-oral fibroblasts to stimulate extracellular matrix reorganization in a model of wound contraction

Intra-oral wounds, like wounds in children, demonstrate privileged healing when compared with adult wounds at extra-oral sites. This study investigated whether this preferential healing is related to an increased ability of oral mucosal fibroblasts to reorganize extracellular matrix (ECM) when compared with their dermal counterparts. ECM reorganization was investigated by means of a fibroblast-populated collagen lattice (FPCL) system. The effect of donor age was also investigated in this system. Differences in ECM reorganization and FPCL contraction were evident: FPCL contraction was more rapid by oral mucosal fibroblasts than dermal fibroblasts (p < 0.01). FPCL contraction was also greater in child (donor < 10 years) than adult (donor > 18 years) oral mucosal fibroblasts (p < 0.01). These differences were not related to phenotypic differences in cell viability (p > 0.5), DNA synthesis (p > 0.05), and cell number (p > 0.5) within the FPCLs, or cellular attachment to collagen (p > 0.07). FPCL contraction was not stimulated by the addition of conditioned medium from oral mucosal or dermal fibroblasts (p > 0.05). These data show that the significantly increased ability of oral mucosal fibroblasts to reorganize ECM in vitro, when compared with dermal fibroblasts, represents a distinct phenotypic contractile difference, rather than differences in their production of soluble mediators or cell attachment to ECM.

Lipopolysaccharide increases cell surface-associated fibronectin in fibroblasts in vitro

This study assessed the fibronectin expression by fibroblasts derived from noninflamed and inflamed gingiva by measuring the amount of cell surface-associated fibronectin and fibronectin released into the medium. The effects of added lipopolysaccharide from Porphyromonas gingivalis, Prevotella nigrescens and Escherichia coli on both types of fibroblasts were also studied. In the absence of lipopolysaccharide, the amounts of the two types of fibronectin were significantly larger in the fibroblasts from inflamed than from noninflamed gingiva. The specific lipopolysaccharide had no effect on the amount of fibronectin released into the medium by either fibroblast type. The amount of cell surface-associated fibronectin increased significantly when lipopolysaccharide (0.1 and 1 microgram/ml) was added to the cells from the noninflamed gingiva (the effect was evident in the order: P. gingivalis>P.nigrescens>E. coli). Lipopolysaccharide from P. gingivalis significantly increased the cell surface-associated fibronectin even at a low concentration of lipopolysaccharide (0.01 microgram/ml). In fibroblasts from the inflamed gingiva, only the lipopolysaccharide from P. gingivalis was effective in increasing the amount of cell surface-associated fibronectin. Our findings showed that the fibronectin expression was increased in the fibroblasts from inflamed gingiva and that lipopolysaccharide from P. gingivalis increased the cell surface-associated fibronectin.

A methodical study of shape changes in human oral cells perturbed by a simulated orthodontic strain in vitro

Cells are known to alter their shape as a response to physical and chemical changes. Mechanical loads applied to teeth produced cellular perturbations resulting in orthodontic movement. An in vitro model was developed to simulate the in vivo strain of orthodontic movement. Calibrated forces were applied to human periodontal ligament cells and buccal mucosal fibroblasts (controls). A biaxial strain-producing device was used to stretch vital cells growth on flexible polytetrafluorethylene membranes. In addition, a new cell adhesive, Cell Tak, was employed to examine the effect of an adhesive substrate on the cellular response to two known loads. The shape changes of unstrained (control) and strained cells were evaluated by time-lapse telemicroscopy, and plots of time-dependent alterations in area and shape were recorded. The fusiform cells became more rounded over a given time of up to 1400 s. The responses appeared to be independent of cell type, the strain employed, and the presence of cell adhesive. Scanning electron microscopy demonstrated, irrespective of cell type, that the surface of stressed cells produced a striking number of microvilli as compared with the relatively smooth-surfaced controls.

Platelet-derived growth factor reduces the inhibitory effects of lipopolysaccharide on gingival fibroblast proliferation

Lipopolysaccharide from a variety of bacterial sources is known to inhibit gingival fibroblast proliferation and synthetic activity and has been implicated in the pathogenesis of periodontal inflammation. However, it may be involved not only in pathogenesis but also be responsible for delayed wound healing following periodontal therapy. The aim of this investigation was to determine whether the inhibitory effect of LPS on gingival fibroblast proliferation could be reversed by growth factors. Human gingival fibroblasts were cultured in the presence of varying concentrations of platelet-derived growth factor (PDGF) or Salmonella enteritidis LPS to determine the optimal concentrations for stimulation and inhibition of proliferation respectively. The effect of PDGF on LPS inhibition of fibroblast proliferation was studied by combining PDGF and LPS together at the outset of the experimental period or adding PDGF to cells which had been previously primed with LPS. Cell proliferation was monitored by incorporation of 3H-thymidine into precipitable DNA. The results indicated that maximal inhibition of fibroblast proliferation was obtained with 50 micrograms/ml LPS and maximal stimulation of proliferation with 5 ng/ml PDGF. PDGF was found to restore the proliferative activity of the cells exposed to LPS to approximately 60% of their control counterparts. A similar value was obtained for cultures exposed to PDGF after an extended priming period of LPS exposure. Subtle differences were noted in the time taken for cells to complete their cell cycle in the various culture conditions and this may reflect variations in subpopulations of cells in their response to various mitogenic stimuli. Overall the results indicate that PDGF has the capacity to significantly negate and reverse the inhibitory effects of LPS on human gingival fibroblast proliferation.

Factors in virulence expression and their role in periodontal disease pathogenesis

The classic progression of the development of periodontitis with its associated formation of an inflammatory lesion is characterized by a highly reproducible microbiological progression of a Gram-positive microbiota to a highly pathogenic Gram-negative one. While this Gram-negative microbiota is estimated to consist of at least 300 different microbial species, it appears to consist of a very limited number of microbial species that are involved in the destruction of periodontal diseases. Among these "putative periodontopathic species" are members of the genera Porphyromonas, Bacteroides, Fusobacterium, Wolinella, Actinobacillus, Capnocytophaga, and Eikenella. While members of the genera Actinomyces and Streptococcus may not be directly involved in the microbial progression, these species do appear to be essential to the construction of the network of microbial species that comprise both the subgingival plaque matrix. The temporal fluctuation (emergence/disappearance) of members of this microbiota from the developing lesion appears to depend upon the physical interaction of the periodontal pocket inhabitants, as well as the utilization of the metabolic end-products of the respective species intimately involved in the disease progression. A concerted action of the end-products of prokaryotic metabolism and the destruction of host tissues through the action of a large number of excreted proteolytic enzymes from several of these periodontopathogens contribute directly to the periodontal disease process.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of endotoxin inhibition of human gingival fibroblast attachment to type I collagen

Bacterial endotoxin inhibits the attachment of human gingival fibroblasts to collagen. The present study attempted to elucidate the possible mechanism of this inhibition. Two mechanisms were considered: direct toxicity to the cells and steric interference. Collagen substrates were prepared by rat type I collagen being air-dried in the wells of 24 multi-well plates. Experimental collagen substrates were treated with 50 micrograms of endotoxin/well, while untreated collagen substrates served as controls. Two mL of cell suspension (10(4) cells/mL) was added to each well, and these were incubated at 37 degrees C for two h. The average cell number/mm2 attached to experimental and control substrates was determined. Cell attachment to endotoxin-treated collagen was inhibited by 78%, compared with that to untreated collagen. The washing of the endotoxin-treated collagen for two h did not affect the inhibition of cell attachment, whereas after 24 h of washing, cell attachment was inhibited by 54%, compared with that to untreated collagen. Pre-incubation of the cells in endotoxin for two h did not affect their attachment to collagen. The addition of fetal calf serum (15%) to the experimental system completely reversed the inhibition of fibroblast attachment to endotoxin-treated collagen. These findings suggest that endotoxin interferes with fibroblast attachment to collagen through a steric phenomenon, possibly by blocking the binding sites on the collagen molecule recognized by the membrane receptor for collagen.

Effect of lipopolysaccharide on proteoglycan synthesis by adult human gingival fibroblasts in vitro

The effect of lipopolysaccharide preparations from Salmonella enteritidis, Bacteroides gingivalis, and Actinobacillus actinomycetemcomitans on human gingival fibroblasts was studied. Lipopolysaccharide from all sources inhibited fibroblast proliferation in the concentration range of 0.5 to 50 micrograms/ml, with the lipopolysaccharide from A. actinomycetemcomitans having the strongest inhibitory effect. Assessment of the effect of lipopolysaccharide on gingival fibroblast metabolism indicated both total protein and proteoglycan synthesis to be inhibited with increasing concentrations of lipopolysaccharide. As for the antiproliferative effect, lipopolysaccharide from A. actinomycetemcomitans had the greatest inhibitory effect on cell synthetic activity. This inhibitory effect was determined by pulse-chase experiments to be a true depression in synthesis. Furthermore, the effect was independent of lipopolysaccharide-induced changes in cell proliferation and prostaglandin synthesis. This study confirmed the toxic effect of lipopolysaccharide on fibroblasts and, in particular, indicated that various lipopolysaccharide preparations vary in their potency to influence cell proliferation and extracellular matrix synthesis.