A model of periodontitis in the rat: effect of lipopolysaccharide on bone resorption, osteoclast activity, and local peptidergic innervation

Objective: To establish and characterise a rat model of periodontitis that reiterates the features of human disease. Methods: Periodontal inflammation was induced by a single injection of 10 mug liposaccharide (LPS) (Salmonella typhimurium) in 1 mul saline into rat mandibular gingiva at the buccomesial aspect of the second molar. Animals were killed after 3, 7 and 10 days, mandibles dissected and sectioned for histological and immunocytochemical analysis. Results: LPS injection resulted in a significant gingival and periodontal inflammation with inflammatory infiltrate, apical migration of the junctional epithelium, interdental bone loss, and activation of osteoclasts at the site of injection 7 and 10 days after injection. At 10 days post injection, there was a significant trend for bone loss on both sides of the mandible. Periodontal inflammation was associated with alteration in the levels of calcitonin gene-related peptide-like immunoreactivity in nerve terminals innervating the inflamed gingival papilla. Conclusion: Intragingival injection of LPS in the rat provides an easily induced reproducible experimental model of periodontal inflammation that reiterates features of human disease.