A Role of Osteoimmunology in Leptin-Regulated Bone Metabolism

描述（由申请方提供）：骨免疫学定义为免疫系统与骨代谢之间的相互作用。这一领域的发展是因为人们认识到，在炎症和压力的时候，骨骼中产生的免疫细胞会分泌能够深刻影响骨骼调节的因子。瘦素是由含脂肪细胞产生的16 kDa脂肪细胞因子。瘦素与下丘脑中央长型受体结合通过降低成骨细胞功能刺激骨丢失。体外研究也表明，瘦素与骨髓基质细胞（BMSC）的直接结合可以促进其向成骨谱系分化。我们假设并产生了初步的数据，表明存在一种新的瘦素介导的骨调节机制。据推测，瘦素在骨髓中通过与免疫细胞如巨噬细胞结合而在外周发挥作用，从而通过BMSC分化和成骨细胞功能的继发性变化间接调节骨量。我们将探索这些骨免疫学相互作用，以更好地定义BMSC的生态位，并确定我们的免疫系统在出生后骨维护中可能发挥的作用。为了探讨我们的假设在瘦素的背景下，我们将采用体外和体内技术。瘦素和瘦素受体缺陷小鼠模型将用于收获原代巨噬细胞和BMSC。将通过使用基于微珠的多通道ELISA（Bio-Rad以BioSide销售）分析巨噬细胞分泌矿化和分化调节细胞因子的能力。还将在存在对照或刺激的巨噬细胞及其产物的情况下监测BMSC的分化。最后，局部瘦素调节体内骨形成将探讨重新种植收获骨髓间充质干细胞在明胶海绵支架皮下。将使用显微CT和免疫组织学技术对所得听小骨进行定性分析。骨免疫学的这一概念意味着在骨髓腔中的创造和影响的循环，并且对于与炎症相关的骨疾病（包括骨质疏松症、癌症向骨的转移、关节炎、骨髓炎和牙周病）的研究具有重要意义。

DESCRIPTION (provided by applicant): Osteoimmunology is defined as the interplay between the immune system and bone metabolism. This field has developed from the realization that during times of inflammation and stress, immune cells generated in the bone secrete factors that can profoundly affect bone regulation. Leptin is a 16 kDa adipocytokine produced by fat-containing cells. Binding of leptin to central long-form receptors in the hypothalamus stimulates bone loss by decreasing osteoblast function. It has also been demonstrated in vitro that direct binding of leptin to bone marrow stromal cells (BMSCs) can promote their differentiation toward an osteogenic lineage. We hypothesize and have generated preliminary data to suggest that a novel third mechanism of leptin-mediated bone regulation exists. It is hypothesized that leptin acts peripherally in the bone marrow by binding to immune cells such as macrophages to indirectly regulate bone mass through secondary changes in BMSC differentiation and osteoblast function. We will explore these osteoimmunologic interactions to better define the niche of the BMSC and to determine the role our immune system may play in post-natal bone maintenance. To explore our hypothesis in the context of leptin we will employ both in vitro and in vivo techniques. Leptin and leptin-receptor deficient mouse models will be utilized for harvest of primary macrophages and BMSCs. Macrophage cells will be analyzed for their ability to secrete mineralization and differentiation-regulating cytokines through the use of bead-based multichannel ELISA, marketed as BioPlex by Bio-Rad. Differentiation of BMSCs will also be monitored in the presence of control or stimulated macrophages and their products. Finally, local leptin regulation of in vivo bone formation will be explored by re-implanting harvested BMSCs subcutaneously in gelfoam scaffolds. The resulting ossicles will be qualitatively analyzed using micro-CT and immunohistological techniques. This concept of osteoimmunology implies a circle of creation and influence in the marrow cavity and has important implications for the study of inflammation-linked bone disorders including osteoporosis, cancer metastasis to the bone, arthritis, osteomyelitis and periodontal disease.