To study anti-inflammatory cytokine effects on RANKL+-T-cell-mediated osteoclastogenesis in vivo, we injected human interleukin-10 (hIL-10) into pathogen-infected HuPBL-NOD/SCID mice. The results show significantly decreased RANKL+ Th1-associated alveolar bone loss and coexpression of human gamma interferon (hIFN-γ) and human macrophage colony-stimulating factor, but not hIL-4, in RANKL+ Th cells compatible with those from successfully treated aggressive periodontitis subjects. Thus, there are critical cytokine interactions linking hIFN-γ+ Th1 cells to RANKL-RANK/OPG signaling for periodontal osteoclastogenesis in vivo.
Recent studies have shown the biological and clinical significance of signaling pathways of osteogenic cytokines RANKL-RANK/OPG in controlling osteoclastogenesis associated with bone pathologies, including rheumatoid arthritis, osteoporosis, and other osteolytic disorders. In contrast to the inhibitory effect of gamma interferon (IFN-γ) on RANKL-mediated osteoclastogenesis reported recently, alternative new evidence is demonstrated via studies of experimental periodontitis using humanized NOD/SCID and diabetic NOD mice and clinical human T-cell isolates from diseased periodontal tissues, where the presence of increasing IFN-γ is clearly associated with (i) enhanced Actinobacillus actinomycetemcomitans-specific RANKL-expressing CD4+ Th cell-mediated alveolar bone loss during the progression of periodontal disease and (ii) a concomitant and significantly increased coexpression of IFN-γ in RANKL(+) CD4+ Th cells. Therefore, there are more complex networks in regulating RANKL-RANK/OPG signaling pathways for osteoclastogenesis in vivo than have been suggested to date.
Periodontal disease (PD) is a chronic inflammation of the tooth supporting soft tissue and alveolar bone due to infection by a select group of gram negative microbes, and leads to tooth loss if untreated. Since mice deficient in CD4+ cells are resistant to infection-induced alveolar bone loss, Th cells have been implicated in bone destructive processes during PD. However, the extent to which different Th-cell subtypes play roles in pathogenesis or host protection remains to be defined, and is likely to vary depending on the dominant microorganism involved. By far the best studied periodontal microbe in PD is Porphyromonas gingivalis. Even though the gram negative anaerobe Tannerella forsythia is also a vital contributor to periodontal bone loss, almost nothing is known about immune responses to this organism. Previous studies from our laboratory have revealed that T. forsythia induces periodontal bone loss in mice, and that this bone loss depends on the bacterially-expressed BspA protein. In this study, we show that T. forsythia activates murine APCs primarily through TLR2-dependent signaling via BspA. Furthermore, T. forsythia infection causes a pronounced Th2 bias, evidenced by T cell expression of IL-5 but not IFN-γ or IL-17 in draining LN. Consistently, deficiencies in TLR2 or STAT6 result in resistance to T. forsythia-induced alveolar bone loss. Thus, TLR2 signaling and Th2 cells play pathogenic roles in T. forsythia-induced alveolar bone destruction.
Periodontitis is a common human chronic inflammatory disease that results in the destruction of the tooth attachment apparatus and tooth loss. Although infections with periopathogenic bacteria such as Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum) are essential for inducing periodontitis, the nature and magnitude of the disease is determined by the host's immune response. Here, we investigate the role played by the NK killer receptor NKp46 (NCR1 in mice), in the pathogenesis of periodontitis. Using an oral infection periodontitis model we demonstrate that following F. nucleatum infection no alveolar bone loss is observed in mice deficient for NCR1 expression, whereas around 20% bone loss is observed in wild type mice and in mice infected with P. gingivalis. By using subcutaneous chambers inoculated with F. nucleatum we demonstrate that immune cells, including NK cells, rapidly accumulate in the chambers and that this leads to a fast and transient, NCR1-dependant TNF-α secretion. We further show that both the mouse NCR1 and the human NKp46 bind directly to F. nucleatum and we demonstrate that this binding is sensitive to heat, to proteinase K and to pronase treatments. Finally, we show in vitro that the interaction of NK cells with F. nucleatum leads to an NCR1-dependent secretion of TNF-α. Thus, the present study provides the first evidence that NCR1 and NKp46 directly recognize a periodontal pathogen and that this interaction influences the outcome of F. nucleatum-mediated periodontitis.
Periodontal disease is a common bacterial-induced inflammatory process in which F. nucleatum and P. gingivalis infections lead to the destruction of the teeth supporting attachment apparatus. Previous reports demonstrated that immune cells aggravate the severity of the disease. However, whether NK cells in general and NKp46 (a major killer receptor expressed by NK cells) in particular, play a protective or destructive role in this disease is unknown. Using mice deficient in NCR1 (the mouse orthlogue of NKp46), we demonstrate that oral infection of mice with F. nucleatum, but not with P. gingivalis results in an NCR1-dependent alveolar bone loss. In addition, we show that F. nucleatum is recognized by NCR1 and NKp46 directly and that this recognition leads to the secretion of TNF-α, a central cytokine critically involved in the pathogenesis of periodontal destruction. Collectively, we show that NCR1 and NKp46 play a critical role in the pathogenesis of F. nucleatum-mediated periodontitis.
The Th1/Th2 cytokines involved in human periodontitis remain unclear; therefore, we established a humanized mouse model to investigate this issue in Actinobacillus actinomycetemcomitans-mediated periodontal infection. Quantitative-PCR analysis clearly demonstrates a predominantly mixed Th1 and Th2 expression profile associated with pathogen-specific cell-mediated immunity via osteoprotegerin ligand (or RANK-L)-mediated alveolar bone destruction in vivo.
Actinobacillus actinomycetemcomitans is associated with localized aggressive periodontitis, a disease characterized by rapid loss of the alveolar bone surrounding the teeth. Receptor activator of NF-κB Ligand (RANKL) and osteoprotegerin (OPG) are two molecules that regulate osteoclast formation and bone resorption. RANKL induces osteoclast differentiation and activation, whereas OPG blocks this process by acting as a decoy receptor for RANKL. The purpose of this study was to investigate the effect of A. actinomycetemcomitans on the expression of RANKL and OPG in human gingival fibroblasts and periodontal ligament cells. RANKL mRNA expression was induced in both cell types challenged by A. actinomycetemcomitans extract, whereas OPG mRNA expression remained unaffected. Cell surface RANKL protein was also induced by A. actinomycetemcomitans, whereas there was no change in OPG protein secretion. A cytolethal distending toxin (Cdt) gene-knockout strain of A. actinomycetemcomitans did not induce RANKL expression, in contrast to its wild-type strain. Purified Cdt from Haemophilus ducreyi alone, or in combination with extract from the A. actinomycetemcomitans cdt mutant strain, induced RANKL expression. Pretreatment of A. actinomycetemcomitans wild-type extract with Cdt antiserum abolished RANKL expression. In conclusion, A. actinomycetemcomitans induces RANKL expression in periodontal connective tissue cells. Cdt is crucial for this induction and may therefore be involved in the pathological bone resorption during the process of localized aggressive periodontitis.
Humanized mouse models offer a challenging possibility to study human cell function in vivo. In the huPBL-SCID-huSkin allograft model human skin is transplanted onto immunodeficient mice and allowed to heal. Thereafter allogeneic human peripheral blood mononuclear cells are infused intra peritoneally to induce T cell mediated inflammation and microvessel destruction of the human skin. This model has great potential for in vivo study of human immune cells in (skin) inflammatory processes and for preclinical screening of systemically administered immunomodulating agents. Here we studied the inflammatory skin response of human keratinocytes and human T cells and the concomitant systemic human T cell response.
As new findings in the inflamed human skin of the huPBL-SCID-huSkin model we here identified: 1. Parameters of dermal pathology that enable precise quantification of the local skin inflammatory response exemplified by acanthosis, increased expression of human β-defensin-2, Elafin, K16, Ki67 and reduced expression of K10 by microscopy and immunohistochemistry. 2. Induction of human cytokines and chemokines using quantitative real-time PCR. 3. Influx of inflammation associated IL-17A-producing human CD4+ and CD8+ T cells as well as immunoregulatory CD4+Foxp3+ cells using immunohistochemistry and -fluorescence, suggesting that active immune regulation is taking place locally in the inflamed skin. 4. Systemic responses that revealed activated and proliferating human CD4+ and CD8+ T cells that acquired homing marker expression of CD62L and CLA. Finally, we demonstrated the value of the newly identified parameters by showing significant changes upon systemic treatment with the T cell inhibitory agents cyclosporine-A and rapamycin.
In summary, here we equipped the huPBL-SCID-huSkin humanized mouse model with relevant tools not only to quantify the inflammatory dermal response, but also to monitor the peripheral immune status. This combined approach will gain our understanding of the dermal immunopathology in humans and benefit the development of novel therapeutics for controlling inflammatory skin diseases.
Human nonobese diabetic-severe combined immune deficiency (NOD-SCID) mouse chimeras have been widely used as an in vivo model to assess human immune function. However, only a small fraction of transferred human T lymphocytes can be detected in human peripheral blood lymphocyte (huPBL)-NOD-SCID chimeras. To improve the reconstitution of human T lymphocytes in NOD-SCID mice, the use of recombinant human interleukin-15 (rhIL-15) as a stimulator of human lymphocytes was explored. Administration of rhIL-15 after transplantation of huPBLs into NOD-SCID mice increased reconstitution of human T lymphocytes in a dose-dependent manner, with an optimal dosage of 1 μg/mouse. The number of human T lymphocytes (HLA-ABC+ CD3+) in the lymphoid organs or tissue of rhIL-15-treated huPBL-NOD-SCID mice increased 11- to 80-fold, and phytohemagglutinin-induced T-lymphocyte proliferation and cytokine production were significantly enhanced. Additionally, although mature human cells have not been thought to enter the murine thymus, human T lymphocytes were detected in the huPBL-NOD-SCID thymus after rhIL-15 treatment. Thus, rhIL-15 can be used to optimize long-term peripheral T-cell engraftment in these human-mouse chimeras and may also be useful in clinical treatment of T-cell deficiencies.
Gingival inflammation, bacterial infection, alveolar bone destruction, and subsequent tooth loss are characteristic features of periodontal disease, but the precise mechanisms of bone loss are poorly understood. Most animal models of the disease require injury to gingival tissues or teeth, and the effects of microorganisms are thus complicated by host responses to tissue destruction. To determine whether three putative periodontal pathogens, Porphyromonas gingivalis, Campylobacter rectus, and Fusobacterium nucleatum, could cause localized bone resorption in vivo in the absence of tissue injury, we injected live or heat-killed preparations of these microorganisms into the subcutaneous tissues overlying the calvaria of normal mice once daily for 6 days and then examined the bones histologically. We found that all three microorganisms (both live and heat killed) stimulated bone resorption and that the strain of F. nucleatum used appeared to be the strongest inducer of osteoclast activity. Treatment of the mice concomitantly with indomethacin reduced but did not completely inhibit bone resorption by these microorganisms, suggesting that their effects were mediated, in part, by arachidonic acid metabolites (e.g., prostaglandins). Our findings indicate that these potential pathogens can stimulate bone resorption locally when placed beside a bone surface in vivo in the absence of prior tissue injury and support a role for them in the pathogenesis of bone loss around teeth in periodontitis.
Background and objective
Young mice do not develop measurable periodontal bone loss, unless heavily infected with human periodontal pathogens. However, mice with genetically altered immune system are unable to control their own oral flora and develop periodontitis early in life. Based on the potential of the indigenous oral microbiota to cause periodontitis, we hypothesized that normal mice may ultimately develop inflammatory periodontal bone loss, i.e., as a function of age. If confirmed, this could serve as an aging model of chronic periodontitis.
Materials and methods
Periodontal bone levels were measured as the distance from the cementoenamel junction (CEJ) to the alveolar bone crest (ABC), in young (8-10 weeks of age), old (≥ 18 months of age), and mice of intermediate ages. Differential expression of inflammatory mediators in the gingivae of young and old mice was determined by quantitative real-time PCR.
In comparison to young mice, old mice displayed significantly (p < 0.05) increased periodontal bone loss, accompanied by elevated expression of proinflammatory cytokines (interleukin-1β, tumor necrosis factor-α, and interleukin-17A) and innate immune receptors involved in the induction or amplification of inflammation (Toll-like receptor 2, CD14, CD11b, CD18, complement C5a receptor, and triggering receptor expressed on myeloid cells-3).
Mice develop naturally-induced periodontal bone loss as a function of age. This aging model of periodontitis represents a genuinely chronic model to study mechanisms of periodontal tissue destruction.
Animal model; Alveolar bone; Chronic periodontitis; Inflammation; Innate immunology
Recombinant human prolactin (rhPRL) was administered to huPBL-SCID mice to determine its effects on production of human immunoglobulin (Ig). The huPBL-SCID mice were injected intraperitoneally (i.p.) with 10 μg rhPRL every other day for a total of 10 injections. The results reconfirmed that rhPRL significantly increased the numbers of human CD3+ T cells and human CD19+ B cells in spleens, lymph nodes, and thymuses of huPBL-SCID mice. The huPBL-SCID mice were then concurrently given various doses of diphtheria-tetanus (DT) vaccine and 10-μg i.p. injections of rhPRL and were examined for the presence of human DT-specific proliferation of lymph node cells in vitro and antibody production in vivo. rhPRL greatly improved the engraftment of functional human lymphocytes (CD3+ T cells and CD19+ B cells) in DT-immunized huPBL-SCID mice. The rhPRL-treated, DT-immunized huPBL-SCID mice produced significantly larger amounts of DT-specific antibodies in response to the vaccine. The predominant Ig isotype induced after immunization was IgG. Thus, rhPRL stimulation promotes human secondary IgG responses in huPBL-SCID mice.
Inflammatory periodontal diseases are a leading cause of tooth loss and are linked to multiple systemic conditions, such as cardiovascular disease and stroke. Reconstruction of the support and function of affected tooth-supporting tissues represents an important therapeutic endpoint for periodontal regenerative medicine. An improved understanding of periodontal biology coupled with current advances in scaffolding matrices has introduced novel treatments that use cell and gene therapy to enhance periodontal tissue reconstruction and its biomechanical integration. Cell and gene delivery technologies have the potential to overcome limitations associated with existing periodontal therapies, and may provide a new direction in sustainable inflammation control and more predictable tissue regeneration of supporting alveolar bone, periodontal ligament, and cementum. This review provides clinicians with the current status of these early-stage and emerging cell- and gene-based therapeutics in periodontal regenerative medicine, and introduces their future application in clinical periodontal treatment. The paper concludes with prospects on the application of cell and gene tissue engineering technologies for reconstructive periodontology.
Periodontal disease is one of the most common infectious diseases of humans. Immune
responses to infection trigger loss of alveolar bone from the jaw and eventual tooth loss.
We investigated the contribution of B cell IgD to alveolar bone loss by comparing the
response of B cell normal BALB/cJ mice and IgD deficient BALB/c-Igh-5−/−J mice to oral infection with Porphyromonas gingivalis, a gram-negative periodontopathic bacterium
from humans. P. gingivalis-infected normal mice lost bone. Specific antibody to P.
gingivalis was lower and oral colonization was higher in IgD deficient mice; yet bone
loss was completely absent. Infection increased the proportion of CD69+ activated B cells
and CD4+ T cells in immune normal mice compared to IgD deficient mice. These data
suggest that IgD is an important mediator of alveolar bone resorption, possibly through
antigen-specific coactivation of B cells and CD4+ T cells.
Periodontitis, a disease responsible for tooth loss worldwide, is characterized by chronic inflammation of the periodontium, eventually leading to destruction of periodontal ligaments and supporting alveolar bone. Spirochetes, identified by dark-field microscopy as being the most predominant bacteria in advanced lesions, are thought to play a causative role. Various spirochetal morphotypes were observed, but most of these morphotypes are as yet uncultivable. To assess the role of these organisms we designed oligonucleotide probes for the identification of both cultivable and so far uncultivable spirochetes in periodontitis patients. Subgingival plaque specimens taken from diseased sites (n = 200) and healthy control sites (n = 44) from 53 patients with rapidly progressive periodontitis (RPP) were submitted to direct in situ hybridization or dot blot hybridization after prior amplification with eubacterial primers. Spirochetes were found in all patients, but their distributions varied considerably. Parallel use of oligonucleotide probes specific for cultivable or so far uncultivable treponemes suggested the presence of novel yet unknown organisms at a high frequency. These uncultivable treponemes were visualized by fluorescence in situ hybridization, and their morphologies, sizes, and numbers could be estimated. All RPP patients included in this study harbored oral treponemes that represent either novel species, e.g., Treponema maltophilum, or uncultivable phylotypes. Therefore, it is necessary to include these organisms in etiologic considerations and to strengthen efforts to cultivate these as yet uncultivable treponemes.
Anemia is a worldwide health problem that manifests in different types. This illness has some causes, which affect body health generally. Studies have shown that some anemia types make humans more sensitive to infections.
A 23-year-old woman was referred to our clinic with complaints about tooth mobility. Generalized severe alveolar bone loss was verified by a radiographic examination. After a comprehensive clinical examination and taking her medical history, we decided to schedule a medical consultation with a physician. Medical consultation revealed that the patient suffered from severe anemia. Her periodontal treatment was modified because of her systemic situation. After treatment, the patient was monitored for one year. Her periodontal and systemic statuses were stable during this period.
In this case report, severe periodontal destruction was observed in a patient with severe iron and B12 deficiency anemia.
Anemia; alveolar bone loss; periodontitis; diagnosis
IL-32 was recently found to be elevated in the tissue of rheumatoid arthritis and inflammatory bowel disease. Periodontitis is a chronic inflammatory disease caused by polymicrobial infections that result in soft tissue destruction and alveolar bone loss. Although IL-32 is also thought to be associated with periodontal disease, its expression and possible role in periodontal tissue remain unclear. Therefore, this study investigated the expression patterns of IL-32 in healthy and periodontally diseased gingival tissue. The expression of IL-32 in cultured human gingival fibroblasts (HGF) as well as effects of autocrine IL-32 on IL-8 production from HGF were also examined.
Periodontal tissue was collected from both healthy volunteers and periodontitis patients, and immunofluorescent staining was performed in order to determine the production of IL-32. Using real-time PCR and ELISA, mRNA expression and protein production of IL-32 in HGF, stimulated by Porphyromonas gingivalis (Pg), were also investigated.
Contrary to our expectation, the production of IL-32 in the periodontitis patients was significantly lower than in the healthy volunteers. According to immunofluorescent microscopy, positive staining for IL-32 was detected in prickle and basal cell layers in the epithelium as well as fibroblastic cells in connective tissue. Addition of fixed Pg
in vitro was found to suppress the otherwise constitutive expression of IL-32 mRNA and protein in HGF. However, recombinant IL-32 in vitro inhibited the expression of IL-8 mRNA by HGF stimulated with Pg. Interestingly, anti-IL-32 neutralizing antibody upregulated the IL-8 mRNA expression in non-stimulated HGF, indicating that constitutive expression of IL-32 in HGF suppressed IL-8 mRNA expression in the absence of bacterial stimulation.
These results indicate that IL-32 is constitutively produced by HGF which can be suppressed by Pg and may play a role in the downregulation of inflammatory responses, such as IL-8 production, in periodontal tissue.
Interleukin-32; periodontal disease; Porphyromonas gingivalis; human gingival fibroblast; Interleukin-8
Periodontitis is a common infectious disease in which the attachment tissues of the teeth and their alveolar bone housing are destroyed, resulting in tooth loss. The gram-negative anaerobic microorganism Porphyromonas gingivalis has been closely linked to severe forms of the disease. We show for the first time that immunization of the primate Macaca fascicularis with killed P. gingivalis in Syntex Adjuvant Formulation-M inhibits progression of periodontal tissue destruction.
Periodontitis is a chronic destructive infection of the tooth-supportive tissues, which is caused by pathogenic bacteria such as Actinobacillus actinomycetemcomitans. A severe form of periodontitis is found in Papillon-Lefèvre syndrome (PLS), an inheritable disease caused by loss-of-function mutations in the cathepsin C gene. Recently, we demonstrated that these patients lack the activity of the polymorphonuclear leukocyte (PMN)-derived serine proteinases elastase, cathepsin G, and proteinase 3. In the present study we identified possible pathways along which serine proteinases may be involved in the defense against A. actinomycetemcomitans. Serine proteinases are capable to convert the PMN-derived hCAP-18 into LL-37, an antimicrobial peptide with activity against A. actinomycetemcomitans. We found that the PMNs of PLS patients released lower levels of LL-37. Furthermore, because of their deficiency in serine proteases, the PMNs of PLS patients were incapable of neutralizing the leukotoxin produced by this pathogen, which resulted in increased cell damage. Finally, the capacity of PMNs from PLS patients to kill A. actinomycetemcomitans in an anaerobic environment, such as that found in the periodontal pocket, seemed to be reduced. Our report demonstrates a mechanism that suggests a direct link between an inheritable defect in PMN functioning and difficulty in coping with a periodontitis-associated pathogen.
Chronic periodontitis is a complex infection initiated by gram-negative bacteria which destroy the supporting structures of the tooth. Recently, it has been recognized that it is the host response to bacterial infection which causes greater destruction of the connective tissue elements, periodontal ligament and alveolar bone in periodontitis. This has led to the development of various host modulating approaches to target cells and their destructive mediators involved in tissue degradation. Chemically modified tetracyclines (CMTs) are derivatives of tetracycline group of drugs which lack antimicrobial action but have potent host modulating affects. They inhibit pathologically elevated matrix metal loproteinases, pro-inflammtory cytokines and other destructive mediators. Bone resorption is also suppressed due to their combined anti-proteinase and apoptotic affects on osteoblasts and osteoclasts, respectively. Development of resistant bacteria and gastrointestinal toxicity seen with parent tetracyclines is not produced by CMTs. Hence, CMTs are viewed as potential therapeutic agents in the management of chronic diseases like periodontitis that involve destruction of connective tissue and bone.
Chemically modified tetracyclines; host modulation; host response; periodontitis
To investigate the role of suppressor of cytokine signaling (SOCS) molecules in periodontal immunity and RANKL-mediated dendritic cell (DC)-associated osteoclastogenesis, we analyzed SOCS expression profiles in CD4+ T cells and the effect of SOCS3 expression in CD11c+ DCs during periodontal inflammation-induced osteoclastogenesis and bone loss in nonobese diabetic (NOD) versus humanized NOD/SCID mice. Our results of ex vivo and in vitro analyses showed that (i) there is significantly higher SOCS3 expression associated with RANKL+ T-cell-mediated bone loss in correlation with increased CD11c+ DC-mediated osteoclastogenesis; (ii) the transfection of CD11c+ DC using an adenoviral vector carrying a dominant negative SOCS3 gene significantly abrogates TRAP and bone-resorptive activity; and (iii) inflammation-induced TRAP expression, bone resorption, and SOCS3 activity are not associated with any detectable change in the expression levels of TRAF6 and mitogen-activated protein kinase signaling adaptors (i.e., Erk, Jnk, p38, and Akt) in RANKL+ T cells. We conclude that SOCS3 plays a critical role in modulating cytokine signaling involved in RANKL-mediated DC-derived osteoclastogenesis during immune interactions with T cells and diabetes-associated severe inflammation-induced alveolar bone loss. Therefore, the development of SOCS3 inhibitors may have therapeutic potential as the target to halt inflammation-induced bone loss under pathological conditions in vivo.
Wingless proteins, termed Wnt, are involved in embryonic development, blood cell differentiation, and tumorigenesis. In mammalian hematopoiesis, Wnt signaling is essential for stem-cell homeostasis and lymphocyte differentiation. Recent studies have suggested that these molecules are associated with cardiovascular diseases, rheumatoid arthritis, and osteoarthritis. Furthermore, Wnt5a signaling is essential for the general inflammatory response of human macrophages. Periodontitis is a chronic inflammatory disease caused by gram-negative periodontopathic bacteria and the resultant host immune response. Periodontitis is characterized by loss of tooth-supporting structures and alveolar bone resorption. There have been no previous reports on Wnt5a expression in periodontitis tissue, and only few study reported the molecular mechanisms of Wnt5a expression in LPS-stimulated monocytic cells. Using RT-PCR, we demonstrated that Wnt5a mRNA expression was up-regulated in chronic periodontitis tissue as compared to healthy control tissue. P. gingivalis LPS induced Wnt5a mRNA in the human monocytic cell line THP-1 with a peak at 4 hrs after stimulation. P. gingivalis LPS induced higher up-regulation of Wnt5a mRNA than E. coli LPS. The LPS receptors TLR2 and TLR4 were equally expressed on the surface of THP-1 cells. P. gingivalis LPS induced IκBα degradation and was able to increase the NF-κB binding activity to DNA. P. gingivalis LPS-induced Wnt5a expression was inhibited by NF-κB inhibitors, suggesting NF-κB involvement. Furthermore, IFN-γ synergistically enhanced the P. gingivalis LPS-induced production of Wnt5a. Pharmacological investigation and siRNA experiments showed that STAT1 was important for P. gingivalis LPS-induced Wnt5a expression. These results suggest that the modulation of Wnt5a expression by P. gingivalis may play an important role in the periodontal inflammatory process and serve a target for the development of new therapies.
Periodontitis is a periodontal tissue infectious disease and the most common cause for tooth loss in adults. It has been linked to many systemic disorders, such as coronary artery disease, stroke, and diabetes. At present, there is no ideal therapeutic approach to cure periodontitis and achieve optimal periodontal tissue regeneration. In this study, we explored the potential of using autologous periodontal ligament stem cells (PDLSCs) to treat periodontal defects in a porcine model of periodontitis. The periodontal lesion was generated in the first molars area of miniature pigs by the surgical removal of bone and subsequent silk ligament suture around the cervical portion of the tooth. Autologous PDLSCs were obtained from extracted teeth of the miniature pigs and then expanded ex vivo to enrich PDLSC numbers. When transplanted into the surgically created periodontal defect areas, PDLSCs were capable of regenerating periodontal tissues, leading to a favorable treatment for periodontitis. This study demonstrates the feasibility of using stem cell-mediated tissue engineering to treat periodontal diseases.
Periodontal ligament stem cells; Periodontal disease; Tissue engineering; Regeneration
Chronic periodontitis is an infectious disease of the periodontium, which includes the gingival epithelium, periodontal ligament and alveolar bone. The signature clinical feature of periodontitis is resorption of alveolar bone and subsequent tooth loss. The Gram-negative oral anaerobe, Porphyromonas gingivalis, is strongly associated with periodontitis, and it has been shown previously that P. gingivalis is capable of invading osteoblasts in a dose- and time-dependent manner resulting in inhibition of osteoblast differentiation and mineralization in vitro. It is not yet clear which receptors and cytoskeletal components mediate the invasive process, nor how the signaling pathways and viability of osteoblasts are affected by bacterial internalization. This study aimed to investigate these issues using an in vitro model system involving the inoculation of P. gingivalis ATCC 33277 into primary osteoblast cultures.
It was found that binding between P. gingivalis fimbriae and integrin α5β1 on osteoblasts, and subsequent peripheral condensation of actin, are essential for entry of P. gingivalis into osteoblasts. The JNK pathway was activated in invaded osteoblasts, and apoptosis was induced by repeated infections.
These observations indicate that P. gingivalis manipulates osteoblast function to promote its initial intracellular persistence by prolonging the host cell life span prior to its intercellular dissemination via host cell lysis. The identification of molecules critical to the interaction between P. gingivalis and osteoblasts will facilitate the development of new therapeutic strategies for the prevention of periodontal bone loss.
Osteoblasts; Porphyromonas gingivalis; Integrins; Cytoskeleton; Signaling; Apoptosis
Repair of tooth supporting alveolar bone defects caused by periodontal and peri-implant tissue destruction is a major goal of reconstructive therapy. Oral and craniofacial tissue engineering has been achieved with limited success by the utilization of a variety of approaches such as cell-occlusive barrier membranes, bone substitutes and autogenous block grafting techniques. Signaling molecules such as growth factors have been used to restore lost tooth support because of damage by periodontal disease or trauma. This paper will review emerging periodontal therapies in the areas of materials science, growth factor biology and cell/gene therapy. Several different polymer delivery systems that aid in the targeting of proteins, genes and cells to periodontal and peri-implant defects will be highlighted. Results from preclinical and clinical trials will be reviewed using the topical application of bone morphogenetic proteins (BMP-2 and BMP-7) and platelet-derived growth factor-BB (PDGF) for periodontal and peri-implant regeneration. The paper concludes with recent research on the use of ex vivo and in vivo gene delivery strategies via gene therapy vectors encoding growth promoting and inhibiting molecules (PDGF, BMP, noggin and others) to regenerate periodontal structures including bone, periodontal ligament and cementum.
angiogenesis; gene therapy; periodontal disease; regeneration; scaffolds; tissue engineering
Accumulated lines of evidence suggest that hyperimmune responses to periodontal bacteria result in the destruction of periodontal connective tissue and alveolar bone. The etiological roles of periodontal bacteria in the onset and progression of periodontal disease (PD) are well documented. However, the mechanism underlying the engagement of periodontal bacteria in RANKL-mediated alveolar bone resorption remains unclear. Therefore, this review article addresses three critical subjects. First, we discuss earlier studies of immune intervention, ultimately leading to the identification of bacteria-reactive lymphocytes as the cellular source of osteoclast-induction factor lymphokine (now called RANKL) in the context of periodontal bone resorption. Next, we consider (1) the effects of periodontal bacteria on RANKL production from a variety of adaptive immune effector cells, as well as fibroblasts, in inflamed periodontal tissue and (2) the bifunctional roles (upregulation vs. downregulation) of LPS produced from periodontal bacteria in a RANKL-induced osteoclast-signal pathway. Future studies in these two areas could lead to new therapeutic approaches for the management of PD by down-modulating RANKL production and/or RANKL-mediated osteoclastogenesis in the context of host immune responses against periodontal pathogenic bacteria.
periodontal pathogenic bacteria; RANKL; bone resorption; osteoimmunology