Mouse Model of Lipopolysaccharide (LPS)-Induced Pulpitis

Pulpitis is an important and prevalent disease within the oral cavity. Thus, animal models are necessary tools for basic research focused on pulpitis. Researchers worldwide often use dogs and miniature pigs to construct animal models of pulpitis. However, gene editing in miniature pigs is difficult, the surgical modeling process is complex, and tooth demineralization time is lengthy. Although some researchers have attempted to establish a mouse model of pulpitis, most models have involved direct exposure of dental pulp. However, the causes of pulpitis vary considerably among individuals, hindering effective research. In this study, we established a mouse model of pulpitis by accessing the pulp cavity, exposing the pulp to lipopolysaccharide (LPS), and then filling the tooth. One day after surgery, we observed many necrotic tissues and extensive inflammatory exudate, including neutrophils, around the coronal cavity preparation. Additionally, we noted many more neutrophils and a small amount of chronic inflammatory cell infiltrates at the junction between inflamed and normal tissue. These findings indicated that our model can be used to explore the early stage of pulpitis. Ten days after surgery, we observed vacuolar degeneration in some fibroblasts and proliferation in others at the distal end of the inflamed tissue. We also noted dilation and congestion of the pulp blood vessels. Therefore, our model can also be used to explore the middle and later stages of pulpitis. Thirty days after surgery, we observed necrosis in the coronal pulp cavity and upper half of the root pulp, indicating that our model can also be used to explore the end stage of pulpitis. This model is easy to establish, shows pulpitis progression in the dental pulp, exhibits a clear inflammatory phenotype, and can be readily combined with gene editing techniques. Accordingly, it is suitable for basic research focused on pulpitis and has substantial practical value. Key features • Lipopolysaccharide (LPS) can induce pulpitis in mice. • The mouse model of LPS-induced pulpitis can be used in basic studies of pulpitis. • After 1 day, the mouse model of LPS-induced pulpitis can demonstrate the main phenotypes of early-stage pulpitis. • After 10 days, the mouse model of LPS-induced pulpitis can display the main phenotypes of middle and late stage pulpitis. Graphical overview Figure 1.Graphical overview of the C57BL/6 mouse model of lipopolysaccharide (LPS)-induced pulpitis.A. Weigh the mouse. B. Anesthetize the mouse. C. Secure the mouse to the surgical pad and expose its oral cavity. D. Open the pulp chamber of the right maxillary first molar. E. Rinse the medullary foramen with 0.9% NaCl solution. Apply a small cotton ball saturated with 1 mg/mL LPS to the medullary foramen for 5 min, then cover the medullary foramen with Esthet-X flow and irradiate the site. F. Perform tissue decalcification and paraffin embedding (sample collection, decalcification, dehydration, wax embedding, and sectioning), followed by Histopathology staining, microscopy examination, image acquisition, and analysis.