optimization-ligature-induced-periodontitis-mouse-model-for

Optimization of the Ligature-induced Periodontitis Mouse Model for Preclinical Research

The experimental model of ligature-induced periodontitis in mice has played a fundamental role in understanding periodontal disease pathogenesis; yet, it ...

University of North Carolina at Chapel Hill

Periodontal disease (PD) is a common dental disease associated with the interaction between dysbiotic oral microbiota and host immunity. It is a prevalent disease, resulting in loss of gingival tissue, periodontal ligament, cementum and alveolar bone. PD is a major form of tooth loss in the adult population. Experimental animal models have enabled the study of PD pathogenesis and are used to test new therapeutic approaches for treating the disease. The ligature-induced periodontitis model has several advantages as compared with other models, including rapid disease induction, predictable bone loss and the capacity to study periodontal tissue and alveolar bone regeneration because the model is established within the periodontal apparatus. Although mice are the most convenient and versatile animal models used in research, ligature-induced periodontitis has been more frequently used in large animals. This is mostly due to the technical challenges involved in consistently placing ligatures around murine teeth. To reduce the technical challenge associated with the traditional ligature model, we previously developed a simplified method to easily install a bacterially retentive ligature between two molars for inducing periodontitis. In this protocol, we provide detailed instructions for placement of the ligature and demonstrate how the model can be used to evaluate gingival tissue inflammation and alveolar bone loss over a period of 18 d after ligature placement. This model can also be used on germ-free mice to investigate the role of human oral bacteria in periodontitis in vivo. In conclusion, this protocol enables the mechanistic study of the pathogenesis of periodontitis in vivo.

An experimental murine model to study periodontitis.

Inflammasomes are a group of multimolecular intracellular complexes assembled around several innate immune proteins. Recognition of a diverse range of microbial, stress and damage signals by inflammasomes results in direct activation of caspase-1, which subsequently induces the only known form of secretion of active interleukin-1β and interleukin-18. Although the importance of interleukin-1β in the periodontium is not questioned, the impact of inflammasomes in periodontal disease and its potential for therapeutics in periodontology is still in its very early stages. Increasing evidence in preclinical models and human data strongly implicate the involvement of inflammasomes in a number of inflammatory, autoinflammatory and autoimmune disorders. Here we review: (a) the currently known inflammasome functions, (b) clinical/preclinical data supporting inflammasome involvement in the context of periodontal and comorbid diseases and (c) potential therapies targeting inflammasomes. To clarify further the inflammasome involvement in periodontitis, we present analyses of data from a large clinical study (n = 5809) that measured the gingival crevicular fluid-interleukin-1β and grouped the participants based on current periodontal disease classifications. We review data on 4910 European-Americans that correlate 16 polymorphisms in the interleukin-1B region with high gingival crevicular fluid-interleukin-1β levels. We show that inflammasome components are increased in diseased periodontal tissues and that the caspase-1 inhibitor, VX-765, inhibits ~50% of alveolar bone loss in experimental periodontitis. The literature review further supports that although patients clinically present with the same phenotype, the disease that develops probably has different underlying biological pathways. The current data indicate that inflammasomes have a role in periodontal disease pathogenesis. Understanding the contribution of different inflammasomes to disease development and distinct patient susceptibility will probably translate into improved, personalized therapies.

Role of inflammasomes in the pathogenesis of periodontal disease and therapeutics.

Emerging evidence suggests comprehensive immune profiling represents a highly promising, yet insufficiently tapped approach to identify potentially prognostic signatures for periodontitis. In this report, we agnostically identified a periodontitis-associated inflammatory expression network with multiple biomarkers identified within gingival crevicular fluid samples from study participants by applying principal component analysis. We identified an IL-17-dominated trait that is associated with periodontal disease and is inversely modified by the level of IL-10. IL-10 mitigated chemokine CXCL5 and CXCL1 expressions in IL-17-stimulated peripheral blood monocytic cells and peripheral blood monocytic cell-derived macrophages. -deficient mice presented more bone loss, which was associated with more  and IL-17-mediated chemokine and cytokine expression at the transcriptional levels in comparison with control wild-type mice in both the -induced experimental murine periodontitis and ligature-induced alveolar bone-loss models. The dampening effect of IL-10 on the excessive signaling of IL-17 appeared to be mediated by innate immune cells populations rather than by gingival epithelial cells, which are the major cell target for IL-17 signaling. Additionally, elevated IL-17 response in -deficient mice specifically elicited an M1-skewing macrophage phenotype in the gingiva that was associated with the advanced bone loss in the ligature model. In summary, IL-17 dominated an inflammatory network characteristic of periodontitis, and IL-10 dampens this excessive IL-17-mediated periodontitis trait.

IL-10 Dampens an IL-17-Mediated Periodontitis-Associated Inflammatory Network.

Periodontal destruction can be the result of different known and yet-to-be-discovered biological pathways. Recent human genetic association studies have implicated interferon-gamma inducible protein 16 (IFI16) and absent in melanoma 2 (AIM2) with high periodontal interleukin (IL)-1β levels and more destructive disease, but mechanistic evidence is lacking. Here, we sought to experimentally validate these observational associations and better understand IFI16 and AIM2's roles in periodontitis.

Interferon activated gene 204 protects against bone loss in experimental periodontitis.

We have previously characterized the main osteoimmunological events that occur during ligature periodontitis. This study aims to determine the polymicrobial community shifts that occur during disease development.

Oral biofilm dysbiosis during experimental periodontitis.

Inflammasome initiates inflammation via the maturation of interleukin-1 beta (IL-1β). Periodontitis is a prevalent, male-biased disease characterized by inflammation-driven bone loss, yet the mechanism(s) of this sex bias is unknown. This study explored whether enhanced inflammasome represents a causal mechanism for this bias. Analyses of three separate human studies (>6,200 samples) show that males have significantly higher IL-1β in the gingival crevicular fluid than females during health and periodontitis. This pattern is experimentally reproduced with different versions of the ligature-induced periodontitis mouse model where males show greater IL-1β secretion than females. The inflammasome drives bone resorption in males but not females as revealed by analyses of inflammasome gene-deletion mice. Pharmacologic treatment with a caspase-1/4 inhibitor reduces inflammatory cell infiltration, dampens osteoclastogenesis signaling (via the receptor activator of nuclear factor-kappa B pathway), and prevents bone resorption in males but not females during experimental periodontitis. While ovariectomized females show no change in their nonresponsiveness to caspase-1/4 inhibition, orchiectomized males no longer respond to the inhibition, suggesting the importance of an intact male reproductive system in the mediation of this inhibition. Thus, our study identifies inflammasome activation as causal for male-biased experimental periodontitis and supports sex-stratified studies to foster future advancement of inflammasome therapeutics in periodontics.

Article	Year
An experimental murine model to study periodontitis. Nature protocols\| PubMed ID: 30218100	2018
Role of inflammasomes in the pathogenesis of periodontal disease and therapeutics. Periodontology 2000\| PubMed ID: 31850638	2020
IL-10 Dampens an IL-17-Mediated Periodontitis-Associated Inflammatory Network. Journal of immunology (Baltimore, Md. : 1950)\| PubMed ID: 32169848	2020
Interferon activated gene 204 protects against bone loss in experimental periodontitis. Journal of periodontology\| PubMed ID: 35404474	2022
Oral biofilm dysbiosis during experimental periodontitis. Molecular oral microbiology\| PubMed ID: 36189827	2022
Inflammasome targeting for periodontitis prevention is sex dependent. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 41144672	2025

Mustafa Girnary

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