School of Stomatology, Dalian Medical University, Dalian, China.
The Affiliated Stomatological Hospital of Dalian Medical University, Dalian, China.
J Oral Rehabil. 2022 Feb;49(2):228-236. doi: 10.1111/joor.13245. Epub 2021 Aug 27.
Dental pulp tissues are rich in pain-related afferent nerve fibers, which originate from primary sensory neurons in the trigeminal ganglion (TG). The mechanisms of central nervous system (CNS) underlying ectopic pain following peripheral inflammation have been reported that the macrophages as inflammatory and immunologic mediators in the TG play an important role in the process of pulpitis and hyperalgesia.
OBJECTIVE(S): To observe the polarization response and dynamic distribution of macrophages in the TG during the development of dental pulp inflammation.
A rat model of pulpitis was established using complete Freund's adjuvant (CFA). Hematoxylin-eosin (HE), immunohistochemistry (IHC), immunofluorescence (IF), toluidine blue (TB) staining, and RT-qPCR were performed to observe the expression of macrophage-related factors in the TG.
The results of IHC staining showed that M2 macrophages labeled with CD206 were observed in the TG of both the control and CFA groups. The statistical analysis indicated that the number of CD206-positive macrophages in the TG increased significantly at 24 h after CFA-induced pulpitis, reached a peak at 2 weeks, and then returned to the normal level after 6 weeks. The ratio of M2/M1 in the CFA groups was significantly lower than that in the control group from 24 to 72 h, and this pattern was reversed at 2 weeks after CFA-induced pulpitis; then, the ratio increased significantly and was maintained at a high level for 4 weeks. RT-qPCR results showed that the expression of IL-10 in the TG increased significantly from 1 to 4 weeks after CFA-induced pulpitis.
The trend of M2 macrophages was opposite to that of M1 macrophages in the TG during the process of pulpitis induced by CFA, which is consistent with the expression of macrophage-related cytokines. Macrophage polarization in the TG may participate in the neuroinflammation response induced by dental pulpitis.
牙髓组织富含与疼痛相关的传入神经纤维，这些纤维起源于三叉神经节（TG）中的初级感觉神经元。已经报道了外周炎症后中枢神经系统（CNS）异位疼痛的机制，即 TG 中的巨噬细胞作为炎症和免疫介质在牙髓炎和痛觉过敏过程中发挥重要作用。
观察牙髓炎症发展过程中 TG 中巨噬细胞的极化反应和动态分布。
采用完全弗氏佐剂（CFA）建立大鼠牙髓炎模型。采用苏木精-伊红（HE）染色、免疫组织化学（IHC）染色、免疫荧光（IF）染色、甲苯胺蓝（TB）染色和 RT-qPCR 观察 TG 中与巨噬细胞相关因子的表达。
IHC 染色结果显示，在对照组和 CFA 组的 TG 中均观察到标记为 CD206 的 M2 巨噬细胞。统计分析表明，CFA 诱导牙髓炎后 24 h TG 中 CD206 阳性巨噬细胞数量明显增加，2 周时达到高峰，6 周后恢复正常水平。CFA 组 M2/M1 比值在 CFA 诱导牙髓炎后 24-72 h 明显低于对照组，2 周后反转；然后，该比值显著增加，并维持在高水平 4 周。RT-qPCR 结果显示，CFA 诱导牙髓炎后 1-4 周 TG 中 IL-10 的表达明显增加。
CFA 诱导牙髓炎过程中，TG 中 M2 巨噬细胞的趋势与 M1 巨噬细胞相反，与巨噬细胞相关细胞因子的表达一致。TG 中巨噬细胞的极化可能参与牙髓炎症引起的神经炎症反应。
