Trap+ Mononuclear Cells in Periosteal Bone Formation

项目摘要/摘要 骨膜的生长和建模发生在皮质骨外表面的骨膜上。 骨膜，覆盖整个骨表面，但包含关节的那部分骨除外 软骨是体内最具成骨能力的组织之一，在皮质扩张中起着关键作用。 在成长过程中。骨膜成骨的机制不同于骨表面的其他区域，如 如骨内膜、继发性海绵和骨小梁重塑等，尽管它具有生理性。 重要的是，当涉及到发生在底层的骨膜过程时，骨膜经常被忽视 皮质骨。骨膜生物学的研究仍然很少，对其了解也很少。从结构上讲， 骨膜由两层组成，与骨膜表面相邻的是一层松散排列的骨膜。 对底层骨骼的生长和修复至关重要的细胞。再往外是一层密密麻麻的 骨膜来源的干细胞(PDSCs)散布于淋巴管、血管和神经末梢。这个 外层微环境是维持PDSCs的利基环境，而内层则提供 骨膜骨形成的成骨微环境。我们已经证明了没有骨骼 巨噬细胞和Trap+单核细胞在CSF-1 OP/OP小鼠(CSF-1-/-)，有趣的是，没有明显的 皮质骨形成。一次注射重组人粒细胞集落刺激因子足以挽救破骨细胞募集和 在CSF-1-/-小鼠中存活。这些结果表明，骨膜巨噬细胞在维持中是必不可少的。 骨膜微环境对骨膜骨形成的影响。此外，我们已经证明了Trap+ 野生型WT小鼠单个核细胞分泌PDGF-BB诱导间充质迁移 基质/干细胞。在Trap+细胞系中敲除PDGF-BB可减少骨膜血管生成和 骨形成但PDSCs和基质蛋白仍存在于骨膜中，提示骨膜 巨噬细胞在维持骨膜动态平衡中起着更为重要的作用。此外，我们还有 机械应力诱导骨膜TRAP+单个核细胞分泌PDGF-BB促进血管生成 以及我们初步数据中的骨骼形成。因此，我们假设骨膜巨噬细胞维持 骨膜和TRAP+单个核细胞的内稳态将PDSCs从外层招募到 血管生成和骨形成的骨膜表面。在这项提案中，我们将首先确定 骨膜巨噬细胞在骨膜动态平衡中的作用然后我们将确定Trap+的功能 单个核细胞，特别是PDSCs被Trap+单核细胞招募的机制 用于骨膜骨形成。最后，我们将验证TRAP+单个核细胞在机械加工中的作用 应力诱导骨膜成骨。

Project Summary/ Abstract Periosteal bone growth and modeling take place in the periosteum at the outer surface of cortical bones. The perioseum, which covers the entire bone surface except the portion of bones that contains articular cartilage, is one of the most osteogenic tissues in the body and plays a critical role in cortical expansion during growth. Periosteal bone formation has different mechanisms from other areas of bone surface such as endosteum, secondary spongiosa and trabecular bone remodeling, etc. Despite its physiological significance, the periosteum is often overlooked when it comes to processes that occur in the underlying cortical bone. Periosteal biology remains little investigated and poorly understood. Structurally, the periosteum is composed of two layers; adjacent to the periosteal bone surface is a layer of loosely packed cells essential for growth and repair of the underlying bone. Further outward is a layer of densely packed periosteum derived stem cells (PDSCs) interspersed with lymphatics, blood vessels and nerve endings. The microenvironment of the outer layer serves as a niche to maintain the PDSCs whilst the inner layer provides an osteogenic microenvironment for periosteal bone formation. We have shown that there are no osteal macrophages and Trap+ mononuclear cells in CSF-1 op/op mice (CSF-1-/-), and interestingly, no obvious cortical bone formation. A single injection of rhM-CSF is sufficient for rescue of osteoclast recruitment and survival in CSF-1-/- mice. These results suggest that periosteal macrophages are essential in maintenance of periosteum microenvironment for periosteal bone formation. Moreover, we have shown that Trap+ mononuclear cells derived from wild WT mice secrete PDGF-BB to induce migration of mesenchymal stromal/stem cells. Knockout of PDGF-BB in the Trap+ cell lineage reduces periosteal angiogenesis and bone formation but PDSCs and matrix proteins are still present in the periosteum, suggesting periosteal macrophages play more important role in maintenance of periosteum homeostasis. In addition, we have found mechanical stress induces periosteal TRAP+ mononuclear cells to secrete PDGF-BB for angiogenesis and bone formation in our preliminary data. Thus, we hypothesize that periosteal macrophages maintain homeostasis of the periosteum and TRAP+ mononuclear cells recruit PDSCs from outward layer to the periosteal surface for angiogenesis and bone formation. In this proposal, we will first determine the role of periosteal macrophages in periosteum homeostasis. We will then determine the function of Trap+ mononuclear cells, specifically, the mechanisms by which PDSCs are recruited by Trap+ mononuclear cells for periosteal bone formation. Finally, we will validate the role of TRAP+ mononuclear cells in mechanical stress-induced periosteal bone formation.