Plasmin is essential in preventing periodontitis in mice

Extracellular vimentin amplifies inflammation: Perspectives for immune injury and therapeutics for periodontitis

Periodontitis is an inflammatory disease triggered by microbial biofilms that promote immune dysfunction and tissue destruction of tooth-supporting tissues. The search for soluble mediators that amplify inflammatory responses and matrix degradation in periodontal tissues has implicated extracellular vimentin (ECV) as a signaling ligand and damage-associated molecular pattern in the pathogenesis of periodontitis. Intracellular vimentin filaments are essential for the structural integrity of cells and the preservation of matrix homeostasis. These are important determinants of health in the periodontium and many other organs. But in inflamed tissues, intracellular vimentin filaments are disassembled. Vimentin is subsequently released from cells into the extracellular space in a soluble form where it drives immune signaling and tissue destruction. We discuss the role of ECV as a signaling molecule in several tissues. We apply these data to understand how in inflammatory diseases like periodontitis, ECV amplifies immune responses that contribute to disease progression. Arising from these data, we consider novel therapeutic opportunities for limiting tissue destruction by targeting ECV for treatment of inflammatory disorders like periodontitis.

Osteogenic Differentiation of Human Gingival Fibroblasts Inhibits Osteoclast Formation

Gingival fibroblasts (GFs) can differentiate into osteoblast-like cells and induce osteoclast precursors to differentiate into osteoclasts. As it is unclear whether these two processes influence each other, we investigated how osteogenic differentiation of GFs affects their osteoclast-inducing capacity. To establish step-wise mineralization, GFs were cultured in four groups for 3 weeks, without or with osteogenic medium for the final 1, 2, or all 3 weeks. The mineralization was assessed by ALP activity, calcium concentration, scanning electron microscopy (SEM), Alizarin Red staining, and quantitative PCR (qPCR). To induce osteoclast differentiation, these cultures were then co-cultured for a further 3 weeks with peripheral blood mononuclear cells (PBMCs) containing osteoclast precursors. Osteoclast formation was assessed at different timepoints with qPCR, enzyme-linked immunosorbent assay (ELISA), TRAcP activity, and staining. ALP activity and calcium concentration increased significantly over time. As confirmed with the Alizarin Red staining, SEM images showed that the mineralization process occurred over time. Osteoclast numbers decreased in the GF cultures that had undergone osteogenesis. TNF-α secretion, a costimulatory molecule for osteoclast differentiation, was highest in the control group. GFs can differentiate into osteoblast-like cells and their degree of differentiation reduces their osteoclast-inducing capacity, indicating that, with appropriate stimulation, GFs could be used in regenerative periodontal treatments.

Ligneous periodontitis exacerbated by Behçet's disease in a patient with plasminogen deficiency and a stop-gained variant PLG c.1468C > T: a case report

BACKGROUND

Plasminogen serves as the precursor to plasmin, an essential element in the fibrinolytic process, and is synthesized primarily in the liver. Plasminogen activation occurs through the action of plasminogen activator, converting it into plasmin. This conversion greatly enhances the fibrinolytic system within tissues and blood vessels, facilitating the dissolution of fibrin clots. Consequently, congenital deficiency of plasminogen results in impaired fibrin degradation. Patients with plasminogen deficiency typically exhibit fibrin deposits in various mucosal sites throughout the body, including the oral cavity, eyes, vagina, and digestive organs. Behcet's disease is a chronic recurrent systemic inflammatory disease with four main symptoms: aphthous ulcers of the oral mucosa, vulvar ulcers, skin symptoms, and eye symptoms, and has been reported worldwide. This disease is highly prevalent around the Silk Road from the Mediterranean to East Asia. We report a case of periodontitis in a patient with these two rare diseases that worsened quickly, leading to alveolar bone destruction. Genetic testing revealed a novel variant characterized by a stop-gain mutation, which may be a previously unidentified etiologic gene associated with decreased plasminogen activity.

CASE PRESENTATION

This case report depicts a patient diagnosed with ligneous gingivitis during childhood, originating from plasminogen deficiency and progressing to periodontitis. Genetic testing revealed a suspected association with the PLG c.1468C > T (p.Arg490*) stop-gain mutation. The patient's periodontal condition remained stable with brief intervals of supportive periodontal therapy. However, the emergence of Behçet's disease induced acute systemic inflammation, necessitating hospitalization and treatment with steroids. During hospitalization, the dental approach focused on maintaining oral hygiene and alleviating contact-related pain. The patient's overall health improved with inpatient care and the periodontal tissues deteriorated.

CONCLUSIONS

Collaborative efforts between medical and dental professionals are paramount in comprehensively evaluating and treating patients with intricate complications from rare diseases. Furthermore, the PLG c.1468C > T (p.Arg490*) stop-gain mutation could contribute to the association between plasminogen deficiency and related conditions.

Plasmin-Mediated Fibrinolysis in Periodontitis Pathogenesis

The hemostatic and inflammatory systems work hand in hand to maintain homeostasis at mucosal barrier sites. Among the factors of the hemostatic system, fibrin is well recognized for its role in mucosal homeostasis, wound healing, and inflammation. Here, we present a basic overview of the fibrinolytic system, discuss fibrin as an innate immune regulator, and provide recent work uncovering the role of fibrin-neutrophil activation as a regulator of mucosal/periodontal homeostasis. We reason that the role of fibrin in periodontitis becomes most evident in individuals with the Mendelian genetic defect, congenital plasminogen (PLG) deficiency, who are predisposed to severe periodontitis in childhood due to a defect in fibrinolysis. Consistent with plasminogen deficiency being a risk factor for periodontitis, recent genomics studies uncover genetic polymorphisms in PLG, encoding plasminogen, being significantly associated with periodontal disease, and suggesting PLG variants as candidate risk indicators for common forms of periodontitis.

The Recruitment and Activation of Plasminogen by Bacteria-The Involvement in Chronic Infection Development

The development of infections caused by pathogenic bacteria is largely related to the specific properties of the bacterial cell surface and extracellular hydrolytic activity. Furthermore, a significant role of hijacking of host proteolytic cascades by pathogens during invasion should not be disregarded during consideration of the mechanisms of bacterial virulence. This is the key factor for the pathogen evasion of the host immune response, tissue damage, and pathogen invasiveness at secondary infection sites after initial penetration through tissue barriers. In this review, the mechanisms of bacterial impact on host plasminogen-the precursor of the important plasma serine proteinase, plasmin-are characterized, principally focusing on cell surface exposition of various proteins, responsible for binding of this host (pro)enzyme and its activators or inhibitors, as well as the fibrinolytic system activation tactics exploited by different bacterial species, not only pathogenic, but also selected harmless residents of the human microbiome. Additionally, the involvement of bacterial factors that modulate the process of plasminogen activation and fibrinolysis during periodontitis is also described, providing a remarkable example of a dual use of this host system in the development of chronic diseases.

The Role of the Plasminogen/Plasmin System in Inflammation of the Oral Cavity

The oral cavity is a unique environment that consists of teeth surrounded by periodontal tissues, oral mucosae with minor salivary glands, and terminal parts of major salivary glands that open into the oral cavity. The cavity is constantly exposed to viral and microbial pathogens. Recent studies indicate that components of the plasminogen (Plg)/plasmin (Pm) system are expressed in tissues of the oral cavity, such as the salivary gland, and contribute to microbial infection and inflammation, such as periodontitis. The Plg/Pm system fulfills two major functions: (a) the destruction of fibrin deposits in the bloodstream or damaged tissues, a process called fibrinolysis, and (b) non-fibrinolytic actions that include the proteolytic modulation of proteins. One can observe both functions during inflammation. The virus that causes the coronavirus disease 2019 (COVID-19) exploits the fibrinolytic and non-fibrinolytic functions of the Plg/Pm system in the oral cavity. During COVID-19, well-established coagulopathy with the development of microthrombi requires constant activation of the fibrinolytic function. Furthermore, viral entry is modulated by receptors such as TMPRSS2, which is necessary in the oral cavity, leading to a derailed immune response that peaks in cytokine storm syndrome. This paper outlines the significance of the Plg/Pm system for infectious and inflammatory diseases that start in the oral cavity.

Fibrin is a critical regulator of neutrophil effector function at the oral mucosal barrier

Tissue-specific cues are critical for homeostasis at mucosal barriers. Here, we report that the clotting factor fibrin is a critical regulator of neutrophil function at the oral mucosal barrier. We demonstrate that commensal microbiota trigger extravascular fibrin deposition in the oral mucosa. Fibrin engages neutrophils through the αMβ2 integrin receptor and activates effector functions, including the production of reactive oxygen species and neutrophil extracellular trap formation. These immune-protective neutrophil functions become tissue damaging in the context of impaired plasmin-mediated fibrinolysis in mice and humans. Concordantly, genetic polymorphisms in PLG, encoding plasminogen, are associated with common forms of periodontal disease. Thus, fibrin is a critical regulator of neutrophil effector function, and fibrin-neutrophil engagement may be a pathogenic instigator for a prevalent mucosal disease.

Sex-specific genetic factors affect the risk of early-onset periodontitis in Europeans

AIMS

Various studies have reported that young European women are more likely to develop early-onset periodontitis compared to men. A potential explanation for the observed variations in sex and age of disease onset is the natural genetic variation within the autosomal genomes. We hypothesized that genotype-by-sex (G × S) interactions contribute to the increased prevalence and severity.

MATERIALS AND METHODS

Using the case-only design, we tested for differences in genetic effects between men and women in 896 North-West European early-onset cases, using imputed genotypes from the OmniExpress genotyping array. Population-representative 6823 controls were used to verify that the interacting variables G and S were uncorrelated in the general population.

RESULTS

In total, 20 loci indicated G × S associations (P < 0.0005), 3 of which were previously suggested as risk genes for periodontitis (ABLIM2, CDH13, and NELL1). We also found independent G × S interactions of the related gene paralogs MACROD1/FLRT1 (chr11) and MACROD2/FLRT3 (chr20). G × S-associated SNPs at CPEB4, CDH13, MACROD1, and MECOM were genome-wide-associated with heel bone mineral density (CPEB4, MECOM), waist-to-hip ratio (CPEB4, MACROD1), and blood pressure (CPEB4, CDH13).

CONCLUSIONS

Our results indicate that natural genetic variation affects the different heritability of periodontitis among sexes and suggest genes that contribute to inter-sex phenotypic variation in early-onset periodontitis.

Plasminogen Receptors and Fibrinolysis

The ability of cells to promote plasminogen activation on their surfaces is now well recognized, and several distinct cell surface proteins have been demonstrated to function as plasminogen receptors. Here, we review studies demonstrating that plasminogen bound to cells, in addition to plasminogen directly bound to fibrin, plays a major role in regulating fibrin surveillance. We focus on the ability of specific plasminogen receptors on eukaryotic cells to promote fibrinolysis in the in vivo setting by reviewing data obtained predominantly in murine models. Roles for distinct plasminogen receptors in fibrin surveillance in intravascular fibrinolysis, immune cell recruitment in the inflammatory response, wound healing, and lactational development are discussed.

Porphyromonas gingivalis initiates coagulation and secretes polyphosphates - A mechanism for sustaining chronic inflammation?

BACKGROUND

Periodontitis is a chronic inflammation resulting in destruction of tooth-supporting bone. Chronic inflammation is characterized by extravascular fibrin deposition. Fibrin is central to destruction of bone; monocytes bind to fibrin and form osteoclasts, thus providing a link between coagulation and the tissue destructive processes in periodontitis. The oral microbiome is essential to oral health. However, local ecological changes, such as increased biofilm formation, result in a dysbiotic microbiome characterized by an increase of protease-producing species e.g. Porphyromonas gingivalis. Proteases initiate inflammation and may cleave coagulation factors. Polyphosphates (polyP) may also provide bacteria with procoagulant properties similar to platelet-released polyP. P. gingivalis has also been found in remote locations related to vascular pathology and Alzheimer's disease.

OBJECTIVES

The aim of this study was to investigate procoagulant activity of ten different species of oral bacteria present in oral health and disease as well as presence of polyP and fibrin formation in planktonic and biofilm bacteria.

METHODS

Oral bacteria were studied for protease production and procoagulant activity. The presence of polyP and formation of fibrin was observed using confocal microscopy.

RESULTS

P. gingivalis showed strong protease activity and was the only species exerting procoagulant activity. Confocal microscopy showed polyP intracellularly in planktonic bacteria and extracellularly after biofilm formation. Fibrin formation emanated from planktonic bacteria and from both bacteria and polyP in biofilm cultures.

CONCLUSIONS

The procoagulant activity of P. gingivalis could explain its role in chronic inflammation, locally in oral tissues as well as in remote locations.

Ligneous Periodontitis in a Patient with Type 1 Plasminogen Deficiency: A Case Report and Review of the Literature

Background

Ligneous periodontitis or destructive membranous periodontal disease is a rare condition involving gingival tissues, which is due to plasminogen deficiency and fibrin deposition. Plasminogen deficiency is an ultrarare autosomal recessive disease. The disease is characterized by gingival enlargement and periodontal tissue destruction that leads to rapid tooth loss despite treatment attempts. A defect in fibrinolysis and abnormal wound healing are the main pathogenesis of this condition. It is caused by mutations in PLG, the gene coding for plasminogen, which results in decreased levels and functional activity. Case Presentation. In this case report, clinical and histopathological findings of a 26-year-old male patient who presented with generalized membranous gingival enlargement are presented. He was the third child of consanguineous parents and had multicystic congenital hydrocephalus at birth. Besides the gingival enlargement, he also presented ligneous conjunctivitis since childhood. The intraoral examination revealed generalized periodontal breakdown. Radiographs showed alveolar bone loss present in every quadrant. All blood investigations were normal except for plasminogen deficiency. A biopsy sample was excised from affected gingiva and a series of histopathological evaluation was performed. Based on clinical and histopathological evidence, a diagnosis of destructive membranous periodontal disease or ligneous periodontitis was made. A clinical exome assay for the PLG gene was also done. It was confirmed as Type 1 plasminogen deficiency.

Conclusion

Ligneous periodontitis has been rarely reported in India. The reasons could be because of the rarity of the disease or missed diagnosis. The need to take a proper history and perform a proper clinical examination and histopathologic evaluation has to be stressed when diagnosing and treating gingival enlargements. If a genetic condition is suspected, genetic screening is also needed. All these will help the clinician in correctly diagnosing the disease and formulating a proper treatment plan for managing the condition.

Plasmin inhibition by bacterial serpin: Implications in gum disease

Tannerella forsythia is a periodontopathogen that expresses miropin, a protease inhibitor in the serpin superfamily. In this study, we show that miropin is also a specific and efficient inhibitor of plasmin; thus, it represents the first proteinaceous plasmin inhibitor of prokaryotic origin described to date. Miropin inhibits plasmin through the formation of a stable covalent complex triggered by cleavage of the Lys³⁶⁸-Thr³⁶⁹ (P2-P1) reactive site bond with a stoichiometry of inhibition of 3.8 and an association rate constant (k_ass) of 3.3 × 10⁵ M^-1s^-1. The inhibition of the fibrinolytic activity of plasmin was nearly as effective as that exerted by α₂-antiplasmin. Miropin also acted in vivo by reducing blood loss in a mice tail bleeding assay. Importantly, intact T. forsythia cells or outer membrane vesicles, both of which carry surface-associated miropin, strongly inhibited plasmin. In intact bacterial cells, the antiplasmin activity of miropin protects envelope proteins from plasmin-mediated degradation. In summary, in the environment of periodontal pockets, which are bathed in gingival crevicular fluid consisting of 70% of blood plasma, an abundance of T. forsythia in the bacterial biofilm can cause local inhibition of fibrinolysis, which could have possible deleterious effects on the tooth-supporting structures of the periodontium.

Novel LRAP-binding partner revealing the plasminogen activation system as a regulator of cementoblast differentiation and mineral nodule formation in vitro

Amelogenin isoforms, including full-length amelogenin (AMEL) and leucine-rich amelogenin peptide (LRAP), are major components of the enamel matrix, and are considered as signaling molecules in epithelial-mesenchymal interactions regulating tooth development and periodontal regeneration. Nevertheless, the molecular mechanisms involved are still poorly understood. The aim of the present study was to identify novel binding partners for amelogenin isoforms in the cementoblast (OCCM-30), using an affinity purification assay (GST pull-down) followed by mass spectrometry and immunoblotting. Protein-protein interaction analysis for AMEL and LRAP evidenced the plasminogen activation system (PAS) as a potential player regulating OCCM-30 response to amelogenin isoforms. For functional assays, PAS was either activated (plasmin) or inhibited (ε-aminocaproic acid [aminocaproic]) in OCCM-30 cells and the cell morphology, mineral nodule formation, and gene expression were assessed. PAS inhibition (EACA 100 mM) dramatically decreased mineral nodule formation and expression of OCCM-30 differentiation markers, including osteocalcin (Bglap), bone sialoprotein (Ibsp), osteopontin (Spp1), tissue-nonspecific alkaline phosphatase (Alpl) and collagen type I (Col1a1), and had no effect on runt-related transcription factor 2 (Runx2) and Osterix (Osx) mRNA levels. PAS activation (plasmin 5 µg/µl) significantly increased Col1a1 and decreased Bglap mRNA levels (p < .05). Together, our findings shed new light on the potential role of plasminogen signaling pathway in the control of the amelogenin isoform-mediated response in cementoblasts and provide new insights into the development of targeted therapies.

Rare Diseases with Periodontal Manifestations

Background: The object of this paper was to provide an overview of rare diseases (RDs) with periodontal manifestations and allocate them to relevant categories. Methods: In ROMSE, a database for “Rare Diseases with Orofacial Involvement”, all 541 entities were analyzed with respect to manifestations of periodontal relevance. Inclusion criteria were periodontally relevant changes to the oral cavity, in accordance with the 2018 version of the Classification of Periodontal and Peri-Implant Diseases and Conditions. Rare diseases were recorded, using the methodology described, and subsequently compared with the Orphanet Classification of Rare Diseases. Results: A total of 76 RDs with periodontal involvement were recorded and allocated in accordance with the Classification of Periodontal and Peri-Implant Diseases and Conditions. Of the 541 RDs analyzed as having known orofacial manifestations, almost 14 percent indicated a periodontally compromised dentition. Conclusions: Around 14 percent of RDs with an orofacial involvement showed periodontally relevant manifestations, which present not only as a result of gingivitis and periodontitis, but also gingival hyperplasia in connection with an underlying disease. Thus, dentists play an important role in therapy and early diagnoses of underlying diseases based on periodontally relevant manifestations.

Urokinase-plasminogen activator protects periodontal ligament fibroblast from oxidative induced-apoptosis and DNA damage

BACKGROUND AND OBJECTIVE

Urokinase-plasminogen activator (uPA) is a serine protease expressed at high basal level in normal gingival cervical fluid. Despite its known pathologic role in tissue proteolysis in periodontitis, little is known concerning uPA physiological function in oral tissue. Recent evidence in cancer cells has implicated the uPA system in DNA repair and anti-apoptotic pathways. This study is aimed to evaluate the protective function of urokinase against oxidative DNA damage in periodontal ligament (PDL) fibroblast, and to propose a new biological role for uPA in oral cavity.

MATERIAL AND METHODS

PDL cells were isolated from human wisdom teeth obtained from healthy donors. An oxidative stress model was created in which PDL cells were incubated with 20, 30, 40 and 60 μmol/L hydrogen peroxide. Twenty-four hours before and after peroxide treatment, cells were treated with uPA and amiloride. Cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay, apoptosis by DAPI-staining and annexin V/propidium iodide assay, and DNA breaks by alkaline comet assay. For estimating DNA damage level, γ-H2AX expression was studied using flow cytometry and immunostaining.

RESULTS

The incubation of the peroxide-treated cells with uPA significantly increased cell viability and decreased apoptosis. A significant decrease in the number of γ-H2AX foci was seen at 30 μmol/L hydrogen peroxide in uPA-treated cells. uPA inhibition as a result of amiloride treatment, in turn, induced a reduction in cell viability. In addition, there was a significant decrease in the levels of DNA damage in uPA-treated groups as measured by the comet assay.

CONCLUSION

The present study brings support to the theory that uPA may have a protective role for periodontal tissue and could protect PDL fibroblasts from oxidative DNA damage and apoptosis.

Plasminogen is a critical regulator of cutaneous wound healing

Wound healing is a complicated biological process that consist of partially overlapping inflammatory, proliferation and tissue remodelling phases. A successful wound healing depends on a proper activation and subsequent termination of the inflammatory phase. The failure to terminate the inflammation halts the completion of wound healing and is a known reason for formation of chronic wounds. Previous studies have shown that wound closure is delayed in plasminogendeficient mice, and a role for plasminogen in dissection of extracellular matrix was suggested. However, our finding that plasminogen is transported to the wound by inflammatory cells early during the healing process, where it potentiates inflammation, indicates that plasminogen may also have other roles in the wound healing process. Here we report that plasminogen-deficient mice have extensive fibrin and neutrophil depositions in the wounded area long after re-epithelialisation, indicating inefficient debridement and chronic inflammation. Delayed formation of granulation tissue suggests that fibroblast function is impaired in the absence of plasminogen. Therefore, in addition to its role in the activation of inflammation, plasminogen is also crucial for subsequent steps, including resolution of inflammation and activation of the proliferation phase. Importantly, supplementation of plasminogen-deficient mice with human plasminogen leads to a restored healing process that is comparable to that in wild-type mice. Besides of being an activator of the inflammatory phase during wound healing, plasminogen is also required for the subsequent termination of inflammation. Based on these results, we propose that plasminogen may be an important future therapeutic agent for wound treatment.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Genes Critical for Developing Periodontitis: Lessons from Mouse Models

Since the etiology of periodontitis in humans is not fully understood, genetic mouse models may pinpoint indispensable genes for optimal immunological protection of the periodontium against tissue destruction. This review describes the current knowledge of genes that are involved for a proper maintenance of a healthy periodontium in mice. Null mutations of genes required for leukocyte cell–cell recognition and extravasation (e.g., Icam-1, P-selectin, Beta2-integrin/Cd18), for pathogen recognition and killing (e.g., Tlr2, Tlr4, Lamp-2), immune modulatory molecules (e.g., Cxcr2, Ccr4, IL-10, Opg, IL1RA, Tnf-α receptor, IL-17 receptor, Socs3, Foxo1), and proteolytic enzymes (e.g., Mmp8, Plasmin) cause periodontitis, most likely due to an inefficient clearance of bacteria and bacterial products. Several mechanisms resulting in periodontitis can be recognized: (1) inefficient bacterial control by the polymorphonuclear neutrophils (defective migration, killing), (2) inadequate antigen presentation by dendritic cells, or (3) exaggerated production of pro-inflammatory cytokines. In all these cases, the local immune reaction is skewed toward a Th1/Th17 (and insufficient activation of the Th2/Treg) with subsequent osteoclast activation. Finally, genotypes are described that protect the mice from periodontitis: the SCID mouse, and mice lacking Tlr2/Tlr4, the Ccr1/Ccr5, the Tnf-α receptor p55, and Cathepsin K by attenuating the inflammatory reaction and the osteoclastogenic response.

Resveratrol suppresses the alveolar bone resorption induced by artificial trauma from occlusion in mice

OBJECTIVE

Besides inflammatory bone loss, trauma from occlusion (TO)-induced alveolar bone loss increases the risk of future tooth loss. We have shown that resveratrol, a polyphenol, possesses anti-inflammatory characteristics and a suppressive effect on osteoclastogenesis. Therefore, we investigated the effects of resveratrol on TO-induced bone loss in mice.

MATERIAL AND METHODS

Trauma from occlusion was induced by overlaying composite resin onto the maxillary first molar of C57BL/6 mice. TO-induced mice were administered either resveratrol or vehicle for 15 days from 5 days before TO induction. The mice administered vehicle only served as controls. The effect of resveratrol on bone resorption was assessed histologically. Gene expression in gingival and periodontal ligament tissues was analyzed. In vitro effect of resveratrol on the differentiation of RAW 264.7 cells and bone marrow-derived macrophages into osteoclastic cells was analyzed.

RESULTS

Resveratrol administration significantly decreased the bone loss and suppressed the elevated expression of osteoclastogenesis-related gene in periodontal ligament tissue by TO. Resveratrol treatment also suppressed the differentiation of both RAW 264.7 cells and bone marrow-derived macrophages into osteoclastic cells.

CONCLUSION

Resveratrol administration suppressed the TO-induced alveolar bone loss by suppressing osteoclast differentiation, suggesting that resveratrol is effective in preventing both inflammation and mechanical stress-induced alveolar bone resorption.

The Role of Proteinase-Activated Receptors 1 and 2 in the Regulation of Periodontal Tissue Metabolism and Disease

Proteinase-activated receptors 1 (PAR1) and 2 (PAR2) are the most highly expressed members of the PAR family in the periodontium. These receptors regulate periodontal inflammatory and repair processes through their activation by endogenous and bacterial enzymes. PAR1 is expressed by the periodontal cells such as human gingival fibroblasts, gingival epithelial cells, periodontal ligament cells, osteoblasts, and monocytic cells and can be activated by thrombin, matrix metalloproteinase 1 (MMP-1), MMP-13, fibrin, and gingipains from Porphyromonas gingivalis. PAR2 is expressed by neutrophils, osteoblasts, oral epithelial cells, and human gingival fibroblasts, and its possible activators in the periodontium are gingipains, neutrophil proteinase 3, and mast cell tryptase. The mechanisms through which PARs can respond to periodontal enzymes and result in appropriate immune responses have until recently been poorly understood. This review discusses recent findings that are beginning to identify a cardinal role for PAR1 and PAR2 on periodontal tissue metabolism.

Enhanced Osteogenesis of ADSCs by the Synergistic Effect of Aligned Fibers Containing Collagen I

The topographical features and material composition of scaffolds have a powerful influence on cell behaviors such as proliferation and differentiation. Here, scaffolds consisting of aligned fibers with incorporated bioactive collagen I were tested for their ability to enhance osteogenesis in vitro. Rat adipose-derived mesenchymal stem cells (ADSCs) were seeded on the scaffolds and their morphology, proliferation, and osteogenic differentiation were examined. Aligned scaffolds with collagen I showed the best osteogenic properties. Also, adhesion-related genes showed the higher expression on aligned scaffolds with collagen I. Our findings indicate that fiber alignment combined with incorporation of collagen I increases the capacity of electrospun scaffolds to induce enhanced and directed osteogenesis. Such scaffolds may, therefore, have potential for improving guided oral bone regeneration.

Relevance of the plasminogen system in physiology, pathology, and regeneration of oral tissues - From the perspective of dental specialties

Plasmin is a proteolytic enzyme that is crucial in fibrinolysis. In oral tissues, the plasminogen system plays an essential role in physiological and pathological processes, which in addition to fibrinolysis include degradation of extracellular matrix, inflammation, immune response, angiogenesis, tissue remodeling, cell migration, and wound healing. Oral tissues reveal a change in the plasminogen system during pathological processes such as periodontitis, peri-implantitis, or pulpitis, as well as in response to mechanical load. The plasminogen system is also a key element in tissue regeneration. The number of studies investigating the plasminogen system in dentistry have grown continuously in recent years, highlighting its increasing relevance in dental medicine. In this review, we present the diverse functions of the plasminogen system in physiology and its importance for dental specialists in pathology and regeneration. We thus provide an overview of the current knowledge on the role of the plasminogen system in the different fields of dentistry, including endodontics, orthodontics, periodontics, and oral surgery.

Co-culture of bone marrow stem cells and macrophages indicates intermediate mechanism between local inflammation and innate immune system in diabetic periodontitis

Diabetic periodontitis (DP), which has been shown to cause alveolar bone loss, is among the most common complications associated with diabetes. The precise mechanisms underlying alveolar bone loss in patients with DP remain unclear. Therefore, the present study established a co-culture system of bone marrow stem cells (BMSCs) and macrophages, in order to investigate the potential mechanisms underlying DP-associated alveolar bone loss in vitro. In addition, Porphyromonas gingivalis (PG) periodontal infection and high glucose levels were used to induce DP in mice. The present study evaluated the protein expression levels of various chemokines and the migration of BMSCs and macrophages. The protein expression levels of extracellular signal-regulated kinase 1 and 2, c-Jun N-terminal kinase and p38 mitogen-activated protein kinase (MAPK) were significantly increased in the BMSCs exposed to high glucose and PG, which may have been due to the activation of MAPK. In addition, DP induction in mice was associated with the release of chemokine (C-C motif) ligand 2 (CCL2) from BMSCs and the secretion of chemokine (C-C Motif) receptor 2 (CCR2) and tumor necrosis factor-α from macrophages, which was associated in turn with enhanced adhesion and chemotaxis of macrophages. The results of the present study suggested that DP led to the upregulation of CCL2 in the periodontal tissues and enhanced macrophage infiltration via the CCL2/CCR2 axis, which in turn promoted alveolar bone loss.

Comparison of Experimental Diabetic Periodontitis Induced by Porphyromonas gingivalis in Mice

Periodontitis is one of the severe complications in diabetic patients and gingival epithelium plays an initial role on the onset and progression of this disease. However the potential mechanism is yet sufficiently understood. Meanwhile, the research on the correlational experimental animal models was also insufficient. Here, we established periodontitis with type 2 diabetes in db/db and Tallyho/JngJ (TH) mice and periodontitis with type 1 diabetes in streptozotocin induced diabetes C57BL/6J (STZ-C57) mice by oral infection of periodontal pathogen Porphyromonas gingivalis W50. We demonstrated that periodontal infected mice with high blood glucose levels showed dramatically more alveolar bone loss than their counterparts, in which infected db/db mice exhibited the most bone defects. No contrary impact could be observed between this periodontal infection and onset and severity of diabetes. The expressions of PTPN2 were inhibited whereas the expression of JAK1, STAT1, and STAT3 increased dramatically in gingival epithelia and the serum TNF-α also significantly increased in the mice with diabetic periodontitis. Our results indicated that the variations of inflammation-related protein expressions in gingival epithelia might lead to the phenotype differences in the mice with diabetic periodontitis.

uPA Attenuated LPS-induced Inflammatory Osteoclastogenesis through the Plasmin/PAR-1/Ca(2+)/CaMKK/AMPK Axis

Chronic inflammatory diseases, such as rheumatoid arthritis and periodontitis-caused bone destruction, results from an increase of bone-resorbing osteoclasts (OCs) induced by inflammation. However, the detailed mechanisms underlying this disorder remain unclear. We herein investigated that the effect of urokinase-type plasminogen activator (uPA) on inflammatory osteoclastogenesis induced by lipopolysaccharide (LPS), which is a potent stimulator of bone resorption in inflammatory diseases. We found that the uPA deficiency promoted inflammatory osteoclastogenesis and bone loss induced by LPS. We also showed that LPS induced the expression of uPA, and the uPA treatment attenuated the LPS-induced inflammatory osteoclastogenesis of RAW264.7 mouse monocyte/macrophage lineage cells. Additionally, we showed that the uPA-attenuated inflammatory osteoclastgenesis is associated with the activation of plasmin/protease-activated receptor (PAR)-1 axis by uPA. Moreover, we examined the mechanism underlying the effect of uPA on inflammatory osteoclastogenesis, and found that uPA/plasmin/PAR-1 activated the adenosine monophosphate-activated protein kinase (AMPK) pathway through Ca2+/calmodulin dependent protein kinase kinase (CaMKK) activation, and attenuated inflammatory osteoclastogenesis by inactivation of NF-κB in RAW264.7 cells. These data suggest that uPA attenuated inflammatory osteoclastogenesis through the plasmin/PAR-1/Ca2+/CaMKK/AMPK axis. Our findings may provide a novel therapeutic approach to bone loss caused by inflammatory diseases.

Periodontitis associated with plasminogen deficiency: a case report

BACKGROUND

Plasminogen deficiency is a rare autosomal recessive disease, which is associated with aggressive periodontitis and gingival enlargement. Previously described treatments of plasminogen deficiency associated periodontitis have shown limited success. This is the first case report indicating a successful therapy approach consisting of a non-surgical supra- and subgingival debridement in combination with an adjunctive systemic antibiotic therapy and a strict supportive periodontal regimen over an observation period of 4 years.

CASE PRESENTATION

The intraoral examination of a 17-year-old Turkish female with severe plasminogen deficiency revealed generalized increased pocket probing depths ranging from 6 to 9 mm, bleeding on probing over 30%, generalized tooth mobility, and gingival hyperplasia. Alveolar bone loss ranged from 30% to 50%. Clinical attachment loss corresponded to pocket probing depths. Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola, Prevotella intermedia, Prevotella nigrescens and Eikenella corrodens have been detected by realtime polymerase chain reaction. Periodontal treatment consisted of full mouth disinfection and adjunctive systemic administration of amoxicillin (500 mg tid) and metronidazole (400 mg tid). A strict supportive periodontal therapy regimen every three month in terms of supra- and subgingival debridement was rendered. The reported therapy has significantly improved periodontal health and arrested disease progression. Intraoral examination at the end of the observation period 3.5 years after non-surgical periodontal therapy showed generalized decreased pocket probing depths ranging from 1 to 6 mm, bleeding on probing lower 30%, and tooth mobility class I and II. Furthermore, microbiological analysis shows the absence of Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola after therapy.

CONCLUSION

Adjunctive antibiotic treatment may alter the oral microbiome and thus, the inflammatory response of periodontal disease associated to plasminogen deficiency and diminishes the risk of pseudomembrane formation and progressive attachment loss. This case report indicates that patients with plasminogen deficiency may benefit from non-surgical periodontal treatment in combination with an adjunctive antibiotic therapy and a strict supportive periodontal therapy regimen.

Epithelial TRPV1 signaling accelerates gingival epithelial cell proliferation

Transient receptor potential cation channel subfamily V member 1 (TRPV1), a member of the calcium-permeable thermosensitive transient receptor potential superfamily, is a sensor of thermal and chemical stimuli. TRPV1 is activated by noxious heat (> 43°C), acidic conditions (pH < 6.6), capsaicin, and endovanilloids. This pain receptor was discovered on nociceptive fibers in the peripheral nervous system. TRPV1 was recently found to be expressed by non-neuronal cells, such as epithelial cells. The oral gingival epithelium is exposed to multiple noxious stimuli, including heat and acids derived from endogenous and exogenous substances; however, whether gingival epithelial cells (GECs) express TRPV1 is unknown. We show that both TRPV1 mRNA and protein are expressed by GECs. Capsaicin, a TRPV1 agonist, elevated intracellular Ca(2+) levels in the gingival epithelial cell line, epi 4. Moreover, TRPV1 activation in epi 4 cells accelerated proliferation. These responses to capsaicin were inhibited by a specific TRPV1 antagonist, SB-366791. We also observed GEC proliferation in capsaicin-treated mice in vivo. No effects were observed on GEC apoptosis by epithelial TRPV1 signaling. To examine the molecular mechanisms underlying this proliferative effect, we performed complementary (c)DNA microarray analysis of capsaicin-stimulated epi 4 cells. Compared with control conditions, 227 genes were up-regulated and 232 genes were down-regulated following capsaicin stimulation. Several proliferation-related genes were validated by independent experiments. Among them, fibroblast growth factor-17 and neuregulin 2 were significantly up-regulated in capsaicin-treated epi 4 cells. Our results suggest that functional TRPV1 is expressed by GECs and contributes to the regulation of cell proliferation.

Endoplasmic reticulum stress response and bone loss in experimental periodontitis in mice

BACKGROUND AND OBJECTIVE

Endoplasmic reticulum (ER) stress is the cell response that activates the unfolded protein response (UPR) pathway in a variety of conditions, such as inflammation and bone metabolism. The UPR may be associated with the pathogenesis of periodontal disease because the disease is inflammatory in nature, and alveolar bone resorption is a characteristic feature of the disease. However, the relationship between ER stress and alveolar bone resorption observed in periodontal disease remains elusive.

MATERIAL AND METHODS

C57BL/6 mice were orally administered Porphyromonas gingivalis, a representative periodontopathic bacterium, in the presence or absence of a chemical chaperone, 4-phenylbutyrate (4-PBA). The gene expression of UPR-related molecules and cytokines in gingival tissues were analyzed using real-time polymerase chain reaction, and alveolar bone resorption and osteoclast numbers were evaluated histologically. The in vitro effect of 4-PBA on the differentiation of mouse bone marrow cells induced by receptor activator of nuclear factor-κB ligand in the presence of macrophage colony-stimulating factor was analyzed.

RESULTS

The gene expression levels of UPR-related molecules and proinflammatory cytokines and alveolar bone resorption were significantly increased in P. gingivalis-administered mice. UPR-related gene expression and alveolar bone resorption were significantly suppressed by the administration of 4-PBA. However, no effect of 4-PBA was observed for proinflammatory cytokine expression in gingival tissues. Osteoclastic differentiation of bone marrow cells was also suppressed by 4-PBA with a concomitant reduction in the gene expression of cathepsin K and tartrate-resistant alkaline phosphatase genes.

CONCLUSION

ER stress induced by oral administration of P. gingivalis is involved in alveolar bone resorption independent of inflammatory cytokines in mice.

Oral pathobiont induces systemic inflammation and metabolic changes associated with alteration of gut microbiota

Periodontitis has been implicated as a risk factor for metabolic disorders such as type 2 diabetes, atherosclerotic vascular diseases, and non-alcoholic fatty liver disease. Although bacteremias from dental plaque and/or elevated circulating inflammatory cytokines emanating from the inflamed gingiva are suspected mechanisms linking periodontitis and these diseases, direct evidence is lacking. We hypothesize that disturbances of the gut microbiota by swallowed bacteria induce a metabolic endotoxemia leading metabolic disorders. To investigate this hypothesis, changes in the gut microbiota, insulin and glucose intolerance, and levels of tissue inflammation were analysed in mice after oral administration of Porphyromonas gingivalis, a representative periodontopathogens. Pyrosequencing revealed that the population belonging to Bacteroidales was significantly elevated in P. gingivalis-administered mice which coincided with increases in insulin resistance and systemic inflammation. In P. gingivalis-administered mice blood endotoxin levels tended to be higher, whereas gene expression of tight junction proteins in the ileum was significantly decreased. These results provide a new paradigm for the interrelationship between periodontitis and systemic diseases.

Evaluation of gingival crevicular fluid levels of tissue plasminogen activator, plasminogen activator inhibitor 2, matrix metalloproteinase-3 and interleukin 1-β in patients with different periodontal diseases

OBJECTIVES

The purpose of this study was to evaluate the gingival crevicular fluid levels of interleukin-1beta (IL-1β), matrix metalloproteinases-3 (MMP-3), tissue type plasminogen activator (t-PA) and plasminogen activator inhibitor 2 (PAI-2) in patients with chronic periodontitis, aggressive periodontitis (AgP) and healthy individuals (controls).

MATERIAL AND METHODS

Systemically healthy (21 chronic periodontitis, 23 AgP and 20 controls) subjects were included in this study. Plaque index, gingival index, probing pocket depth and clinical attachment level were recorded and gingival crevicular fluid samples were collected. Assays for IL-1β, MMP-3, t-PA and PAI-2 levels in gingival crevicular fluid were carried out by an enzyme-linked immunosorbent assay. The one-sample Kolmogorov-Smirnov test, Mann-Whitney U test and Spearman correlation coefficient were used for data analyses.

RESULTS

Gingival crevicular fluid levels of t-PA and IL-1β were significantly higher in chronic periodontitis and AgP groups than in the control group (p < 0.001). MMP-3 levels in gingival crevicular fluid were detected as significantly higher in the chronic periodontitis and AgP groups compared with the control group (p < 0.05). The t-PA/PAI-2 rate of patients with chronic periodontitis and AgP were significantly higher than the control group (p < 0.05). The positive correlations were found among the PAI-2, t-PA, IL-1β and MMP-3 levels in gingival crevicular fluid. The volume of the gingival crevicular fluid correlated with all of the clinical parameters (p < 0.001). There were positive correlations between the gingival crevicular fluid levels of PAI-2 and the probing pocket depth and between gingival crevicular fluid levels of PAI-2 and the clinical attachment level (p < 0.01). Similarly, significant correlations were found between t-PA levels and probing pocket depth and between t-PA levels and clinical attachment level measurements (p < 0.001).

CONCLUSION

The present data showed that gingival crevicular fluid levels of IL-1 β, MMP-3 and t-PA increased in periodontal disease regardless of the periodontitis type and played a part in tissue destruction.

New insights into the role of Plg-RKT in macrophage recruitment

Plasminogen (PLG) is the zymogen of plasmin, the major enzyme that degrades fibrin clots. In addition to its binding and activation on fibrin clots, PLG also specifically interacts with cell surfaces where it is more efficiently activated by PLG activators, compared with the reaction in solution. This results in association of the broad-spectrum proteolytic activity of plasmin with cell surfaces that functions to promote cell migration. Here, we review emerging data establishing a role for PLG, plasminogen receptors and the newly discovered plasminogen receptor, Plg-RKT, in macrophage recruitment in the inflammatory response, and we address mechanisms by which the interplay between PLG and its receptors regulates inflammation.

L-mimosine and dimethyloxaloylglycine decrease plasminogen activation in periodontal fibroblasts

BACKGROUND

The use of prolyl hydroxylase inhibitors such as l-mimosine (L-MIM) and dimethyloxaloylglycine (DMOG) to improve angiogenesis is a new approach for periodontal regeneration. In addition to exhibiting pro-angiogenic effects, prolyl hydroxylase inhibitors can modulate the plasminogen activator system in cells from non-oral tissues. This study assesses the effect of prolyl hydroxylase inhibitors on plasminogen activation by fibroblasts from the periodontium.

METHODS

Gingival and periodontal ligament fibroblasts were incubated with L-MIM and DMOG. To investigate whether prolyl hydroxylase inhibitors modulate the net plasminogen activation, kinetic assays were performed with and without interleukin (IL)-1. Moreover, plasminogen activators and the respective inhibitors were analyzed by casein zymography, immune assays, and quantitative polymerase chain reaction.

RESULTS

The kinetic assay showed that L-MIM and DMOG reduced plasminogen activation under basal and IL-1-stimulated conditions. Casein zymography revealed that the effect of L-MIM involves a decrease in urokinase-type plasminogen activator activity. In agreement with these findings, reduced levels of urokinase-type plasminogen activator and elevated levels of plasminogen activator inhibitor 1 were observed.

CONCLUSION

L-MIM and DMOG can reduce plasminogen activation by fibroblasts from the gingiva and the periodontal ligament under basal conditions and in the presence of an inflammatory cytokine.

25-Hydroxyvitamin D3 attenuates experimental periodontitis through downregulation of TLR4 and JAK1/STAT3 signaling in diabetic mice

Vitamin D has been known to be closely associated with diabetes and periodontitis while the underlying mechanism has yet to be clarified. The present study aimed to discover the effect of 25-hydroxyvitamin D3 (25-OHD3) on glycemic control and periodontal health in mice with periodontitis superimposed on experimental diabetes (known as diabetic periodontitis). We showed that 25-OHD3 intraperitoneal injection attenuated diabetic periodontitis by reducing serum fasting blood glucose, glycosylated hemoglobin and TNF-α levels, which led to decreased alveolar bone loss. Immunohistochemical staining and western blot analysis of gingival epithelia revealed that vitamin D receptor (VDR) expression was enhanced upon 25-OHD3 treatment, while toll-like receptor 4 (TLR4) expression was reduced. The expressions of Janus family kinase (JAK) 1 and signal transducer and activator of transcription (STAT) 3 as well as their phosphorylation were inhibited in gingival epithelia of diabetic periodontitis mice, whereas the expression and phosphorylation of STAT1 remained unchanged. These results suggest that 25-OHD3 could improve diabetic periodontitis through downregulation of TLR4 and JAK1/STAT3 signaling in the gingival epithelium. Our study extends the previous findings on the regulation of diabetes with periodontitis, and may also provide a potential therapy for the patients with this disease.

Effects of surface functionalization of PLGA membranes for guided bone regeneration on proliferation and behavior of osteoblasts

Covalent immobilization of bioactive compounds onto modified poly lactic-co-glycolic acid (PLGA) surfaces is being rapidly developed in tissue engineering, but the compounds and the grafting procedure require optimization. Here, PLGA membranes were grafted with various ratios of collagen/chitosan (COL/CHI) composites after modification by polydopamine and then analyzed using attenuated total reflectance Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and a contact angle meter. Mechanical properties of the membranes were examined by tensile testing. Proliferation of osteoblastic cell line MC3T3-E1 cultured on the membranes was examined by MTT (3-(4, 5-dimethylthiozole-2-yl)-2, 5-diphenyltetrazolium bromide) and flow cytometric analysis. Effects on cell behavior, including cytotaxis, adhesion, and migration, were further investigated by continuous time-lapse imaging for 8 h. The COL/CHI composites were successfully immobilized onto PLGA surfaces. PLGA mainly contributed the mechanical properties, while COL/CHI played a major role in bioactivity. COL facilitated cell adhesion and spread, but the addition of CHI decreased both. A critical ratio of COL/CHI (2:1) above which the addition of CHI only slightly impacted cell proliferation was found. The results should be useful for combining versatile materials from different origins to construct guided bone regeneration membranes and to further optimize the ratio of COL/CHI composites.