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 has not been fully leveraged for translational and therapeutic applications. Similar to human disease, ligature-induced periodontitis in mice develops via a series of distinct microbial, inflammatory, and osteo-immunological events. The ligature-induced alveolar bone destruction progresses in a reasonably short period and is easily quantifiable, making it a cost-effective disease model for preclinical studies. To overcome the technical challenge of the classic ligature model, the establishment of the simplified ligature-induced periodontitis mouse model was curated. Rather than inducing disease in the entire circumference of two adjacent teeth, the simplified disease model is centered on inflammatory bone destruction only in the interproximal region of two posterior teeth, which is also the region that common periodontal disease initiates in humans. Because it employs three dimensional (3D)-printed tools for ligature placement, the approach is fast and effective  leading to a procedural time of 5-10 min per mouse. While osteoclastogenic signaling is detected after 3 days of ligature placement, bone destruction consistently develops at 9 days post ligation. Here, the simplified ligature model protocol is elaborated by highlighting important elements specific to study design (i.e., power calculation, procedure standardization, calibration), development of the 3D printed tools (i.e., the "mouse dental bed" and "ligature holder"), and alveolar bone quantification using μCT analysis. Gingival gene expression of Rank, Rankl, and Opg, a master regulatory triad of osteoclastogenesis, is used as indirect evidence of therapeutic effectiveness. The methods presented in this paper will guide investigators' implementation of the simplified ligature-induced periodontitis model to test innovative periodontal therapeutics in the preclinical setting.