miR-155通过TLR4/MyD88/NF-κB途径调控巨噬细胞极化在PTH促进下颌骨牵张成骨中的作用机制研究

甲状旁腺激素（Parathyroid hormone, PTH）加速牵张成骨的调控机制尚未完全阐明。有研究表明巨噬细胞表型转化后可促进组织再生，miR-155表达下调后具有抑制M1型巨噬细胞活性和促进成骨双重效应。我们前期研究显示PTH可提升成骨细胞功能而促进下颌骨牵张成骨，但PTH能否转化巨噬细胞表型而促进骨再生及其作用机制尚不清楚。本研究拟在PTH促进牵张成骨研究基础上，检测巨噬细胞在牵张区新骨中的数量和表型变化，研究PTH对巨噬细胞的募集作用及其对骨再生改建的影响；检测牵张成骨过程中miR-155表达变化，体内体外实验研究PTH对miR-155表达的调节作用，并应用miR-155 agomir和miR-155 antagomir研究TLR4/MyD88/NF-κB通路中主要信号分子的表达效应，阐明PTH转化巨噬细胞表型的调控机制，为临床转化应用PTH缩短牵张成骨疗程提供新的理论依据。

The molecular mechanisms of parathyroid hormone (PTH) for accelerating new bone formation during distraction osteogenesis has not been fully clarified. The immunomodulation transition of macrophage phenotype has been shown to play important roles in tissue regeneration, and the downregulation of miR-155 have been shown to suppress the M1 phenotype macrophage activation and promote bone regeneration. Our previous studies have found that the intermittent administration of parathyroid hormone can promote the new bone formation during mandibular distraction osteogenesis via increasing the numbers and functions of osteoblasts. However, whether PTH can modulate a macrophage phenotype and its underlying mechanisms for accelerating bone formation during mandibular distraction osteogenesis remains unclear. In this study, a rabbit mandibular distraction osteogenesis model through intermittent administration of parathyroid hormone will be established to explore the mechanisms of macrophage polarization in bone formation. During the healing process of mandibular distraction, the temporal and spatial expression patterns of macrophage phenotype in the distracted new bone tissue will be identified by flow cytometry, immunofluorescence and immunohistochemistry. In addition, the regulation of PTH on miR-155 expression and the relationship between the expression of miR-155 and osteogenic growth factors will be investigated in vivo and in vitro. Furthermore, the molecular expression of TLR4/MyD88/NF-κB signal pathway mediated by miR-155 agomir and miR-155 antagomir will be detected through quantitative polymerase chain reaction, Western blotting, ELISA and IHC analysis. The purpose of this study is to examine the actions of PTH on the recruitment of macrophage and the expression of miR-155, and to investigate the mechanisms of macrophage polarization mediated by miR-155 via TLR4/MyD88/NF-κB signal pathway and provide theoretical support for the clinical translational application of parathyroid hormone to accelerate the bone formation during mandibular distraction osteogenesis.