The Role of Macrophages in PTH Directed Osseous Wound Healing

 描述(申请人提供)：拔牙、牙周治疗或种植体植入后，口腔骨伤口愈合效果不佳会导致严重的不适和功能减退。更好地了解正常的伤口愈合以及受损伤口愈合的机制将有助于制定治疗策略，以预防健康和系统性挑战患者的并发症。甲状旁腺激素(PTH1-34)是一种合成代谢剂，在动物模型中间歇给药时也能促进拔牙槽的愈合，并促进人类口腔骨的愈合。对于骨的合成代谢作用，已经提出了几种机制，但对其促进骨伤口愈合的能力知之甚少。甲状旁腺素增加成熟成骨细胞的凋亡，然后被吞噬细胞吞噬，这一过程被称为泡腾作用。据推测，这些吞噬细胞主要是交替激活的(M2)巨噬细胞，并被甲状旁腺素进一步上调。M2巨噬细胞参与清除损伤部位的凋亡细胞，继而触发因子(转化生长因子和白介素10)的释放，以促进炎症的消退。进一步证明，转化生长因子通过干细胞募集来刺激成骨细胞的形成。据推测，通过M2巨噬细胞的吞噬作用可促进甲状旁腺激素驱动的骨创伤愈合。有两个目的被提出：1)确定M2巨噬细胞和胞吐作用在口腔骨创伤愈合中的作用；2)确定一种称为乳脂球E8(MFG-E8)的桥接蛋白在甲状旁腺素增强的口腔骨伤口愈合中介导胞吐作用的作用。为了实现这些目标，M2巨噬细胞将被消融(通过抗CD206多肽)或增强(通过IL-4注射)，以确定在一个具有良好特征的拔牙模型中对M2巨噬细胞促进骨创伤愈合的依赖。拔牙窝的显微CT和组织学分析将评估硬组织和软组织的愈合情况。巨噬细胞群将用免疫组织化学和流式细胞仪分析来表征。为了评估吞噬作用在眼窝愈合中的作用，将对缺乏MFG-E8(KO)的小鼠的伤口愈合进行评估。此外，甲状旁腺激素将用于MFG-E8KO和WT小鼠，以研究泡腾作用减少对甲状旁腺素引导拔牙槽愈合的影响。鉴于甲状旁腺素具有增强口腔骨创伤的强大治疗潜力，阐明正常和甲状旁腺素诱导的口腔骨创伤愈合的细胞机制将有助于有效治疗愈合不良状态。

 DESCRIPTION (provided by applicant): Ineffective oral osseous wound healing post tooth extraction, periodontal therapy or implant placement can cause severe discomfort and decreased function. Better understanding of normal wound healing as well as the mechanisms of compromised wound healing will aid in the development of therapeutic strategies to prevent complications in healthy and systemically challenged patients. Parathyroid hormone (PTH 1-34) is an anabolic agent that also increases healing of extraction sockets when administered intermittently in animal models and facilitates oral bone healing in humans. Several mechanisms have been proposed for the anabolic actions in bone, yet little is known regarding its ability to facilitate osseous wound healing. PTH increases apoptosis of mature osteoblasts which are then engulfed by phagocytic cells, a process termed efferocytosis. It is hypothesized that these phagocytic cells are predominantly alternatively activated (M2) macrophages and are further upregulated by PTH. M2 macrophages are implicated in the removal of apoptotic cells at the site of injury which then triggers the release of factors (TGFß and IL10) to promote the resolution of inflammation. TGFß has been further shown to stimulate osteoblastogenesis through stem cell recruitment. It is hypothesized that efferocytosis via M2 macrophages enhances PTH-driven osseous wound healing. Two aims are proposed: 1) to identify the role of M2 macrophages and efferocytosis during oral osseous wound healing, and 2) to determine the role of a bridging protein termed milk fat globule E8 (MFG-E8) in mediating efferocytosis in PTH-enhanced oral osseous wound healing. To accomplish these aims, M2 macrophages will be either ablated (via anti-CD206 peptide) or enhanced (via IL-4 administration) to determine the dependence on M2 macrophages for osseous wound healing in a well characterized tooth extraction model. Micro-CT and histological analyses of extraction sockets will be evaluated for hard and soft tissue healing. Macrophage populations will be characterized using immunohistochemical and flow cytometric analyses. To assess the role of efferocytosis in socket healing, mice lacking MFG-E8 (KO) will be evaluated for wound healing. In addition, PTH will be administered to MFG-E8KO and WT mice to investigate the effect of diminished efferocytosis on PTH directed healing of extraction sockets. Given the strong therapeutic potential of PTH to enhance oral osseous wounds, delineating the cellular mechanisms involved in normal and PTH-directed oral osseous wound healing will aid in the effective treatment of inadequate healing states.