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2022, Vol. 26 ›› Issue (14): 2167-2171Changes in the expression of bromodomain-containing protein 4, an epigenetic molecule, in a rat model of chronic periapical periodontitisXu Yinghua1, Jiang Long2, Shi Chun3
Abstract: BACKGROUND: Apical periodontitis is an infectious inflammatory disease of the periapical tissue caused by bacterial infection. Bromodomain-containing protein 4 (BRD4) plays a central role in epigenetic transmission. Studies have shown that BRD4 exerts an important role in inflammation and bone destruction; however, its role in chronic apical periodontitis has not yet been reported. OBJECTIVE: To establish a rat model of apical periodontitis to detect the role of BRD4 in the development of apical periodontitis. METHODS: Thirty Sprague-Dawley rats were selected and randomly divided into five groups, 0-week group, 1-week group, 2-week group, 3-week group, and 4-week group, with six rats in each group. Dental pulp of the left mandibular first molar was exposed by pulpectomy, and they were sacrificed at 0, 1, 2, 3, and 4 weeks postoperatively. After paraformaldehyde fixation, the mandible was removed, and Micro-CT was taken to identify whether the animal model of periapical periodontitis was successfully constructed. Frozen sections were made 1 month after decalcification, and the role of BRD4 in the development of chronic apical periodontitis was detected by immunohistochemistry. RESULTS AND CONCLUSION: The results of Micro-CT showed that widened periodontal ligament and a certain apical shadow appeared in the rat apical periodontitis model at 1-2 weeks postoperatively. The shadow area increased over time and increased significantly at 3 and 4 weeks (P < 0.05). The apical shadow area in the 1-, 2-, 3-, and 4-week groups was significantly higher than that of the 0-week group P < 0.05). However, there was no statistical difference between the 3- and 4-week groups (P > 0.05). Immunohistochemical results showed that the expression of BRD4 in the 1-, 2-, 3-, and 4-week groups was significantly higher than that of the 0-week group (P < 0.05). Highest BRD4 expression appeared in the 2-week group (P < 0.05), but there was no significant difference between the 1- and 4-week groups (P > 0.05). To conclude, BRD4 plays a certain role in the occurrence and development of apical periodontitis, suggesting that BRD4 participates in the development of chronic apical periodontitis. Key words:bromodomain-containing protein 4, chronic apical periodontitis, animal model, oral cavity, periodontal ligament, rat |