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1.  Functional human T-cell immunity and osteoprotegerin ligand control alveolar bone destruction in periodontal infection  
Periodontitis, a prime cause of tooth loss in humans, is implicated in the increased risk of systemic diseases such as heart failure, stroke, and bacterial pneumonia. The mechanisms by which periodontitis and antibacterial immunity lead to alveolar bone and tooth loss are poorly understood. To study the human immune response to specific periodontal infections, we transplanted human peripheral blood lymphocytes (HuPBLs) from periodontitis patients into NOD/SCID mice. Oral challenge of HuPBL-NOD/SCID mice with Actinobacillus actinomycetemcomitans, a well-known Gram-negative anaerobic microorganism that causes human periodontitis, activates human CD4+ T cells in the periodontium and triggers local alveolar bone destruction. Human CD4+ T cells, but not CD8+ T cells or B cells, are identified as essential mediators of alveolar bone destruction. Stimulation of CD4+ T cells by A. actinomycetemcomitans induces production of osteoprotegerin ligand (OPG-L), a key modulator of osteoclastogenesis and osteoclast activation. In vivo inhibition of OPG-L function with the decoy receptor OPG diminishes alveolar bone destruction and reduces the number of periodontal osteoclasts after microbial challenge. These data imply that the molecular explanation for alveolar bone destruction observed in periodontal infections is mediated by microorganism-triggered induction of OPG-L expression on CD4+ T cells and the consequent activation of osteoclasts. Inhibition of OPG-L may thus have therapeutic value to prevent alveolar bone and/or tooth loss in human periodontitis.
This article may have been published online in advance of the print edition. The date of publication is available from the JCI website, J. Clin. Invest. 106:R59–R67 (2000).
PMCID: PMC3102542  PMID: 10995794
3.  Involvement of SOCS3 in Regulation of CD11c+ Dendritic Cell-Derived Osteoclastogenesis and Severe Alveolar Bone Loss ▿  
Infection and Immunity  2009;77(5):2000-2009.
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.
PMCID: PMC2681769  PMID: 19255186
4.  The Use of Rodent Models to Investigate Host-Bacteria Interactions Related to Periodontal Diseases 
Even though animal models have limitations they are often superior to in vitro or clinical studies in addressing mechanistic questions and serve as an essential link between hypotheses and human patients. Periodontal disease can be viewed as a process that involves four major stages: bacterial colonization, invasion, induction of a destructive host response in connective tissue and a repair process that reduces the extent of tissue breakdown. Animal studies should be evaluated in terms of their capacity to test specific hypotheses rather than their fidelity to all aspects of periodontal disease initiation and progression. Thus, each of the models described below can be adapted to test discrete components of these four major steps, but not all of them. This review describes five different animal models that are appropriate for examining components of host-bacteria interactions that can lead to breakdown of hard and soft connective tissue or conditions that limit its repair as follows: the mouse calvarial model, murine oral gavage models with or without adoptive transfer of human lymphocytes, rat ligature model and rat Aggregatibacter actinomycetemcomitans feeding model.
PMCID: PMC2649707  PMID: 18199146
animal model; bacteria; bone; cytokine; inflammation; infection; mouse; murine; osteoclast; periodontitis; rat
5.  Interleukin-10 Inhibits Gram-Negative-Microbe-Specific Human Receptor Activator of NF-κB Ligand-Positive CD4+-Th1-Cell- Associated Alveolar Bone Loss In Vivo  
Infection and Immunity  2006;74(8):4927-4931.
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.
PMCID: PMC1539589  PMID: 16861684
6.  Gamma Interferon Positively Modulates Actinobacillus actinomycetemcomitans-Specific RANKL+ CD4+ Th-Cell-Mediated Alveolar Bone Destruction In Vivo  
Infection and Immunity  2005;73(6):3453-3461.
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.
PMCID: PMC1111859  PMID: 15908374
7.  Mixed Periodontal Th1-Th2 Cytokine Profile in Actinobacillus actinomycetemcomitans-Specific Osteoprotegerin Ligand (or RANK-L)- Mediated Alveolar Bone Destruction In Vivo  
Infection and Immunity  2002;70(9):5269-5273.
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.
PMCID: PMC128282  PMID: 12183580

Results 1-7 (7)