T CELLS AND PTH INDUCED BONE LOSS

T 细胞和 PTH 诱导的骨丢失

基本信息

批准号：
8098913
负责人：
ROBERTO PACIFICI
金额：
$ 30.64万
依托单位：
EMORY UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2007
资助国家：
美国
起止时间：
2007-08-24 至 2012-06-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Primary hyperparathyroidism (PHP) is a common cause of accelerated bone loss and osteoporosis. In spite of extensive investigation the mechanism of the bone catabolic action of PTH has not been not been completely elucidated. PHP is also an important cause of increased bone turnover, which is an independent risk factor for fractures. Studies in 4 in vivo and 5 in vitro models suggest that T cells provide survival, proliferative and pro-osteoclastogenic signals to bone marrow (BM) stromal cells (SCs) through the membrane-bound costimulatory molecule CD40L. As a result, T cell deficient mice are protected against PTH induced bone loss. This is due to the fact that BM SCs derived from T cell deficient mice are fewer in number, produce lower amounts of osteoclastogenic cytokines, and lack the capacity to support PTH induced osteoclast (OC) formation. The capacity of T cells to upregulate both the number and the osteoclastogenic activity of SCs is abolished by silencing of the PTH receptor PPR in T cells. We thus hypothesize that PTH directly stimulates T cells to promote SC osteoclastogenic activity by signaling through the PTH receptor PPR, and that T cells regulate SC number and activity through CD40L. The goal of this application is to determine the mechanism by which T cells mediate the bone catabolic activity of PTH. In Specific Aim 1 we will determine the phenotype of the T lymphocytes which are regulated by PTH, and mediate PTH induced bone loss. This will be accomplished by evaluating the effect of continuous PTH treatment in mice lacking specific T cell subsets. In Aim 2 we will determine the role of direct PPR signaling in T cells in PTH induced OC formation and bone loss. This will be accomplished by utilizing T cells from conditional KO mice which lack the PTH receptor in T cells. We will also determine if PPR signaling in T cells stimulate OC formation by generating T cell signals which upregulate the osteoclastogenic activity of SCs, and if PPR signaling in T cells increases their production of RANKL, TNF and IL-1, and their expression of CD40L. In Aim 3 we will determine if the capacity to regulate SC osteoclastogenic activity in a spontaneous fashion (as opposed to in response to PTH stimulation) and if in vivo silencing of CD40L prevent the increase in SC osteoclastogenic activity, OC formation and bone loss induced by PTH. The discovery of new mechanisms of action of PTH is relevant to public health as it may lead to the identification of novel therapeutic targets for PHP, osteoporosis and the bone disease associated with end stage renal disease. Our studies may also provide insights on strategies for augmenting the anabolic activity of intermittent PTH treatment. One such strategy could be that of antagonizing T cell production of osteoclastogenic factors.

描述（由申请人提供）：原发性甲状旁腺功能亢进症（PHP）是加速骨质流失和骨质疏松症的常见原因。尽管进行了广泛的研究，但 PTH 骨分解代谢作用的机制尚未完全阐明。 PHP 也是骨转换增加的重要原因，而骨转换是骨折的独立危险因素。 4 个体内模型和 5 个体外模型的研究表明，T 细胞通过膜结合共刺激分子 CD40L 向骨髓 (BM) 基质细胞 (SC) 提供生存、增殖和促破骨细胞生成信号。因此，T 细胞缺陷小鼠可以免受 PTH 诱导的骨质流失。这是因为源自 T 细胞缺陷小鼠的 BM SC 数量较少，产生的破骨细胞因子含量较低，并且缺乏支持 PTH 诱导的破骨细胞 (OC) 形成的能力。 T 细胞中 PTH 受体 PPR 的沉默会消除 T 细胞上调 SC 数量和破骨细胞活性的能力。因此，我们假设 PTH 通过 PTH 受体 PPR 信号直接刺激 T 细胞促进 SC 破骨细胞活性，并且 T 细胞通过 CD40L 调节 SC 数量和活性。本申请的目的是确定 T 细胞介导 PTH 骨分解代谢活性的机制。在具体目标 1 中，我们将确定受 PTH 调节并介导 PTH 诱导的骨质流失的 T 淋巴细胞的表型。这将通过评估持续 PTH 治疗对缺乏特定 T 细胞亚群的小鼠的效果来实现。在目标 2 中，我们将确定 T 细胞中直接 PPR 信号传导在 PTH 诱导的 OC 形成和骨质流失中的作用。这将通过利用 T 细胞中缺乏 PTH 受体的条件性 KO 小鼠的 T 细胞来实现。我们还将确定 T 细胞中的 PPR 信号传导是否通过产生上调 SC 破骨细胞活性的 T 细胞信号来刺激 OC 形成，以及 T 细胞中的 PPR 信号传导是否增加其 RANKL、TNF 和 IL-1 的产生以及 CD40L 的表达。在目标 3 中，我们将确定是否能够以自发方式（而不是响应 PTH 刺激）调节 SC 破骨细胞活性，以及 CD40L 的体内沉默是否可以阻止 SC 破骨细胞活性的增加、OC 形成和由甲状旁腺激素。 PTH 新作用机制的发现与公众健康相关，因为它可能导致 PHP、骨质疏松症和与终末期肾病相关的骨病的新治疗靶点的确定。我们的研究还可能为增强间歇性 PTH 治疗的合成代谢活性的策略提供见解。其中一种策略可能是拮抗 T 细胞产生破骨细胞因子。