Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.
Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.
Int Endod J. 2021 Aug;54(8):1328-1341. doi: 10.1111/iej.13514. Epub 2021 Mar 31.
To profile molecular changes in lipopolysaccharide (LPS)-induced experimental pulpitis in a rat model and explore the feasibility of a molecular-based diagnostic strategy for pulpitis.
Seventy-three maxillary incisors of Sprague-Dawley rats were used to establish pulpitis models with LPS. Inflammatory grading was performed in four equal sections of the pulp divided from the injured site to the root apex. An antibody array was used to compare the expression of 67 molecules between control pulp and inflamed pulp 12 and 72 h after LPS application. The levels of differentially expressed molecules in the control and inflamed pulp (collected at 3, 6, 9, 12, 24 and 72 h after LPS treatment) were examined via ELISA, and correlations between inflammatory scores and molecule expression were assessed. The molecule distributions in the pulp were investigated by immunofluorescence staining. Data were analysed with paired t-test, one-way anova, Kruskal-Wallis tests, and Spearman's and Pearson's correlations with significance set at P < 0.05.
Polymorphonuclear neutrophils were observed in the injured site 3 h after LPS stimulation. Inflammatory infiltration peaked at 12 h and was limited to the injured site with osteodentine deposition at 72 h. Thirteen molecules were significantly differentially expressed between the control and LPS-injured pulp. ELISA validated that tissue inhibitor of metalloproteinase-1 (TIMP-1) expression dramatically peaked at 12 h (compared with other time points, P < 0.05) and returned to baseline at 72 h. The TIMP-1 concentration was strongly correlated with inflammation severity in the apical three-quarters of the pulp, and the strongest correlation was found in the lower-middle quarter (r = 0.786, P < 0.001). Immunofluorescence staining revealed that in the apical three-quarters of the pulp, TIMP-1 expression was significantly higher in the 12 h group than in the control and 3, 6, 24 and 72 h groups (P < 0.01).
This study provides a molecular profile of LPS-induced pulpitis in a rat model. TIMP-1 had a strong positive correlation with the severity of dental pulp inflammation, verifying the feasibility of applying biomarkers to identify specific pathological conditions in pulpitis.
分析脂多糖（LPS）诱导的大鼠实验性牙髓炎模型中的分子变化，并探讨基于分子的牙髓炎诊断策略的可行性。
采用 LPS 建立 73 只 SD 大鼠上颌切牙牙髓炎模型。将从损伤部位到根尖的牙髓分为 4 等份，对每份样本进行炎症分级。采用抗体芯片比较 LPS 作用后 12 和 72 h 时对照牙髓和炎性牙髓中 67 种分子的表达。通过 ELISA 检测 LPS 处理后 3、6、9、12、24 和 72 h 时对照和炎性牙髓中差异表达分子的水平，并评估炎症评分与分子表达之间的相关性。通过免疫荧光染色研究牙髓中分子的分布。采用配对 t 检验、单因素方差分析、Kruskal-Wallis 检验、Spearman 和 Pearson 相关性分析，以 P<0.05 为差异有统计学意义。
LPS 刺激后 3 h 即可在损伤部位观察到多形核白细胞。12 h 时炎症浸润达到高峰，72 h 时局限于损伤部位并伴有骨样牙本质沉积。在对照和 LPS 损伤牙髓之间有 13 种分子表达明显不同。ELISA 验证组织金属蛋白酶抑制剂-1（TIMP-1）的表达在 12 h 时明显达到峰值（与其他时间点相比，P<0.05），72 h 时恢复基线。TIMP-1 浓度与牙髓根尖三分之二部位的炎症严重程度呈强相关，与中下三分之一部位的相关性最强（r=0.786，P<0.001）。免疫荧光染色显示，在牙髓根尖三分之二部位，12 h 组 TIMP-1 的表达明显高于对照组和 3、6、24 和 72 h 组（P<0.01）。
本研究提供了 LPS 诱导的大鼠牙髓炎模型的分子谱。TIMP-1 与牙髓炎症严重程度呈强正相关，验证了应用生物标志物识别牙髓炎特定病理状态的可行性。
