OVARIECTOMY UPREGULATES BONE TURNOVER THROUGH T CELL-STROMAL CROSSTALK

描述（由申请人提供）：自然绝经或卵巢切除术（ovx）诱导的雌激素（E）产生停止后，会出现一段时间的快速骨丢失，这有助于绝经后骨质疏松症的发展。OVX诱导的骨丢失是由破骨细胞（OC）数量和活性的刺激引起的，而骨形成的增加不能充分补偿破骨细胞的数量和活性。ovx改变骨吸收和骨形成的机制尚不完全清楚。我们已经报道了由活化T细胞的扩增骨髓（BM）池产生的TNF的增强在OVX诱导的骨丢失中起关键作用。我们的数据表明，BM T细胞主要位于破骨细胞（OC）附近，ovx增加了接近重塑骨内膜表面的T细胞数量。因此，我们假设OVX通过诱导T细胞在骨内膜骨表面附近的壁龛中产生TNF而引起骨丢失。因此，在目的1中，我们将研究OVX诱导的OC和T细胞共定位增加是刺激骨吸收的原因还是结果。这将通过将来自E replete和ovx小鼠的T细胞转移到E replete和ovx小鼠中以及分别用PTH或阿仑膦酸盐预处理以增加或减少骨吸收的WT小鼠中来实现。我们还将在体外研究T细胞和OC之间的相互作用。初步数据表明，T细胞刺激基质细胞（SC）的增殖和存活，增加SC支持OC形成的能力，增加SC产生破骨细胞生成细胞因子，并通过T细胞表达的CD 40 L刺激SC中的CD 40信号传导促进SC分化为OB。因此，在目标2中，我们将确定CD 40 L/CD 40介导的T细胞-SC串扰对SC破骨细胞生成活性、骨吸收和骨丢失增加的贡献。在目的3中，我们将研究CD 40 L/CD 40介导的T细胞-SC串扰在OVX诱导的成骨细胞生成和骨形成的代偿刺激中的作用。为了实现这些目标，我们将利用两种实验模型，用抗CD 40 L抗体MR-1处理的WT ovx小鼠，和首先通过抗CD 4/8抗体耗尽T细胞，然后用来自CD 40 L缺失小鼠的T细胞重建的WT ovx小鼠。该项目与公共卫生相关，因为可能导致更好地表征雌激素在骨中的作用机制，证明T淋巴细胞和骨细胞之间的联系，并确定骨质疏松症的新治疗靶点。

DESCRIPTION (provided by applicant): The cessation of estrogen (E) production induced by natural menopause or ovariectomy (ovx) is followed by a period of rapid bone loss which is instrumental for the development of postmenopausal osteoporosis. Ovx induced bone loss is caused by a stimulation of osteoclast (OC) number and activity insufficiently compensated by an increase in bone formation. The mechanisms by which ovx alters bone resorption and formation are not completely understood. We have reported that enhanced production of TNF by an expanded bone marrow (BM) pool of activated T cells plays a key role in ovx induced bone loss. Our data show that BM T cells are primarily localized near osteoclasts (OC) and that ovx increases the number of T cells in close proximity to remodeling endosteal surfaces. We thus hypothesize that ovx causes bone loss by inducing T cell production of TNF in niches near endosteal bone surfaces. Therefore, in Aim 1 we will investigate weather the ovx induced increased colocalization of OC and T cells is a cause or a consequence of stimulated bone resorption. This will be achieved by transferring T cells from E replete and ovx mice into E replete and ovx mice and in WT mice pretreated with PTH or Alendronate to increase or decrease bone resorption, respectively. We will also investigate the interactions between T cells and OCs in vitro. Preliminary data demonstrate that T cells stimulate proliferation and survival of stromal cells (SCs), increase the capacity of SCs to support OC formation, increase SC production of osteoclastogenic cytokines, and promote SC differentiation into OBs through stimulation of CD40 signaling in SCs by T cell expressed CD40L. Thus, in Aim 2 we will determine the contribution of the CD40L/CD40 mediated T cell-SC crosstalk to the increase in SC osteoclastogenic activity, bone resorption and bone loss. In Aim 3 we will investigate the role of the CD40L/CD40 mediated T cell-SC crosstalk in the compensatory stimulation of osteoblastogenesis and bone formation induced by ovx. To accomplish these goals we will utilize two experimental models, WT ovx mice treated with the anti CD40L antibody MR-1, and WT ovx mice first depleted of T cells by anti CD4/8 antibodies, and then reconstituted with T cells from CD40L null mice. This project is relevant for public health as may lead to a better characterization of the mechanism of action of estrogen in bone, demonstrate a link between T lymphocytes and bone cells, and identify novel therapeutic targets for osteoporosis.