FABP4-UCP2信号轴介导代谢重编程诱导巨噬细胞M2极化在根尖周炎骨破坏中的作用研究

M2 polarization of macrophages plays a crucial role in regulating inflammatory bone destruction. Recent studies have shown that the FABP4-UCP2 axis can mediate metabolic reprogramming to regulate macrophage polarization, but the specific mechanism remains unclear. Previously, the applicant found that Enterococcus faecalis, the dominant pathogen responsible for persistent apical periodontitis, can promote bone resorption by inducing M1 polarization of murine macrophages, where the variation in FABP4-UCP2 expression was significant. Therefore, it is reasonable to propose a hypothesis that whether the intervention of the FABP4-UCP2 axis can promote M2 polarization of macrophages, re-establish the bone-remodeling balance, and inhibit periapical bone destruction. To validate this hypothesis, this project aims to establish a model of periapical periodontitis in mice infected with Enterococcus faecalis and explore the mechanism of FABP4-UCP2 reprogramming in metabolic-regulating macrophage polarization in vitro experiment using metabolic analysis and RNA sequencing techniques under the premise of a clear expression trend of the axis during the bone resorption process. Furthermore, co-culture models of reprogramming macrophages and osteoblasts/osteoclasts will be constructed to clarify the mechanism by which FABP4-UCP2 inhibits bone destruction by regulating cell polarization and animal experiments will also be performed to verify the regulation function. This study is expected to reveal the regulatory mechanism of macrophage polarization transition and its role in remodeling bone balance from a new perspective involving immunometabolism. Moreover, the research will provide the possibility of fresh viewpoints regarding the treatment of bone destruction in persistent apical periodontitis.

巨噬细胞的M2极化对炎症性骨破坏具有关键调节作用。新近研究显示FABP4-UCP2信号轴可介导代谢重编程调控巨噬细胞极化，但具体机制不明。申请人前期发现持续性根尖周炎优势致病菌粪肠球菌经诱导小鼠巨噬细胞M1极化促进骨吸收，该过程细胞FABP4-UCP2差异表达明显。那么能否通过干预FABP4-UCP2信号轴促进巨噬细胞M2极化，重塑局部骨平衡，抑制根尖周骨破坏？本项目拟建立粪肠球菌感染的小鼠根尖周炎模型，明确信号轴在病变过程的定位表达和变化趋势；采用代谢分析及RNA-seq技术，体外实验探讨FABP4-UCP2经代谢重编程调控巨噬细胞极化的机制；继而构建重编程巨噬细胞与成骨/破骨细胞共培养模型，明确FABP4-UCP2通过调节细胞极化抑制骨破坏的机制；动物实验验证其调控作用。本研究有望从免疫代谢新视角揭示巨噬细胞极化转换的调控机制及其重塑骨平衡的作用，为持续性根尖周炎骨破坏的治疗提供新思路

持续性根尖周炎(persistent apical periodontitis, PAP)是根管持续感染导致的慢性根尖周病损，常伴有渐进性骨质破坏，可引起患牙脱落，是牙髓根尖周疾病临床治疗的难点之一。然而，关于持续性根尖周炎的发生发展，以及骨破坏过程的具体机制，目前尚未明确。本项目在前期研究的基础上，进一步对持续性根尖周炎优势致病菌粪肠球菌感染导致的炎症性骨损伤进程展开研究。首先，本项目通过构建小鼠颅骨感染性骨损伤模型，证实了巨噬细胞在粪肠球菌感染所致骨破坏进程中确具关键作用。粪肠球菌感染主要通过激活局部小鼠单核/巨噬细胞，引发高水平炎症反应促进局部破骨细胞的形成与活化，导致骨缺损。以上研究结果提示，针对巨噬细胞进行免疫调节可作为持续性根尖周炎临床治疗的新策略。其次，本项目证实在感染的巨噬细胞极化改变的同时，其代谢调控网络亦发生改变，表现为糖酵解代谢增强而氧化磷酸化代谢抑制；通过抑制细胞糖酵解代谢，可促使巨噬细胞的极化模式由M1型向M2型转变，这表明通过调节巨噬细胞代谢反应，可对巨噬细胞的免疫行为进行调控，此为持续性根尖周炎的防治提供了新的实验基础及理论依据。最后，鉴于促炎的M1型巨噬细胞和破骨细胞形成亢进在骨破坏中的关键作用，抑制巨噬细胞的炎症反应或诱导使其分化形成抗炎的M2表型，同时抑制破骨细胞生成，已成为炎症性骨吸收可能的治疗策略。为此，本项目收集了缺氧状态下牙髓干细胞分泌的囊泡，用于治疗小鼠颅骨感染性骨损伤，由此证实该囊泡可有效抑制巨噬细胞M1型极化而促进M2极化，同时下调破骨细胞的形成活化，从而对感染性骨缺损起一定治疗作用。综上，以上结果推动了根尖周炎分子生物学研究的拓展深化，为根尖周炎中炎症及骨丧失的治疗提供新的理论依据。