Regulation of hemopoietic stem cell expansion by calciotrophic hormones

描述（由申请人提供）：本申请的目的是确定T淋巴细胞如何增加卵巢切除术（ovx）和甲状旁腺激素（PTH）扩大造血干细胞（hsc）的能力。Ovx已知可以增加骨髓（BM）中造血细胞的数量，我们的初步数据显示Ovx可以增加T淋巴细胞充满而T淋巴细胞缺乏小鼠的造血干细胞数量。初步数据显示，T淋巴细胞通过表达共刺激分子CD40L和分泌可溶性IL-6受体（sIL-6R）参与ovx诱导的HSC扩增，可溶性IL-6受体是HSC响应造血细胞因子IL-6所需的受体亚基。数据还表明，阻断T淋巴细胞共刺激分子CD40L可阻止T淋巴细胞上调基质细胞（SCs） Jagged1和IL-6的表达。Jagged1是一种Notch配体，在造血干细胞中激活Notch信号。IL-6是一种造血细胞因子。基于这些数据，我们假设ovx通过T细胞CD40L介导的SC Jagged1和IL-6产生的刺激来扩增hsc。PTH已被证明通过上调SC中Jagged1和IL-6的表达来扩增hsc。我们的初步数据显示，PTH不能增加T细胞缺陷小鼠和缺乏T细胞共刺激分子CD40L的小鼠的hsc数量。另外的数据显示，PTH不会增加在T细胞中表达沉默PTH受体的小鼠造血干细胞的数量，这意味着PTH可以直接靶向T细胞。我们还假设T细胞通过诱导sc中Wnt信号的激活来促进PTH诱导的HSC扩增。在特异性目标1中，我们将确定T细胞促进PTH诱导的造血干细胞扩增的机制。具体来说，我们将研究T细胞产生的因子包括Wnt配体、sIL-6R和CD40L在激活SCs中的Wnt信号和hsc中的Notch信号中的作用。在Specific Aim 2中，我们将确定PTH是否需要直接靶向T细胞来诱导造血干细胞的增殖。这将通过利用我们实验室产生的在T细胞中表达沉默的甲状旁腺激素受体的小鼠来完成。在特异性目标3中，我们将研究T淋巴细胞产生的Wnt配体、sIL-6R和CD40L在激活ovx小鼠sc中的Wnt信号和hsc中的Notch信号中的作用。缺乏关于ovx和PTH通过T细胞扩增造血干细胞的机制的信息是理解造血细胞和骨细胞之间串扰的关键障碍。我们的提议有可能减少这一障碍。如果项目的目标得以实现，我们对两种关键的钙化激素——雌激素和甲状旁腺激素的作用机制的理解将会增加。关于T淋巴细胞在雌激素和甲状旁腺激素调节造血干细胞机制中的作用的新数据将增加骨免疫学这一新的多学科研究领域的广度和深度。

DESCRIPTION (provided by applicant): The goal of this application is to determine how T lymphocytes increase the capacity of ovariectomy (ovx) and parathyroid hormone (PTH) to expand hemopoietic stem cells (HSCs). Ovx is known to increase the number of hemopoietic cells in the bone marrow (BM) and our preliminary data show that ovx increase the number of HSCs in T lymphocyte replete but not T lymphocyte deficient mice. Preliminary data show that T lymphocytes contribute to the HSC expansion induced by ovx by expressing the costimulatory molecule CD40L and by secreting soluble IL-6 receptor (sIL-6R), a receptor subunit required for HSCs to respond to the hemopoietic cytokine IL-6. Data also show that blockade of the T lymphocytes costimulatory molecule CD40L prevents T lymphocytes from upregulating stromal cells (SCs) Jagged1 and IL-6 expression. Jagged1 is a Notch ligand which activates Notch signaling in HSCs. IL-6 is a hemopoietic cytokine. Based on these data we hypothesize that ovx expands HSCs through T cell CD40L mediated stimulation of SC Jagged1 and IL-6 production. PTH has been shown to expand HSCs by upregulating the SC expression of Jagged1 and IL-6. Our preliminary data show that PTH fails to increase the number of HSCs in T cell deficient mice and in mice lacking the T cell costimulatory molecule CD40L. Additional data show that PTH does not increase the number of HSCs in mice expressing a silent PTH receptor in T cells, implying a role for direct targeting of T cells by PTH. We also hypothesize that T cell contribute to the HSC expansion induced by PTH by inducing the activation of Wnt signaling in SCs. In Specific Aim 1 we will determine the mechanism by which T cells contribute to expansion of HSCs induced by PTH. Specifically we will investigate the role of T cell produced factors including Wnt ligands, sIL-6R, and CD40L in activating Wnt signaling in SCs and Notch signaling in HSCs. In Specific Aim 2 we will determine whether direct targeting of T cells by PTH is required for the hormone to induce the expansion of HSCs. This will be accomplished by utilizing a mouse generated in our laboratory which expresses a silent PTH receptor in T cells. In Specific Aim 3 we will investigate the role the role of T lymphocytes produced Wnt ligands, sIL-6R, and CD40L in activating Wnt signaling in SCs and Notch signaling in HSCs in ovx mice. Lack of information about the mechanisms by which ovx and PTH expand HSCs through T cells is a critical barrier to progress of the understanding the cross-talk between hemopoietic cells and bone cells. Our proposal has the potential to decrease this barrier. If the aims of the projects are achieved our understanding of the mechanism of action of two key calciotrophic hormones, estrogen and parathyroid hormone, will be increased. New data about the role of T lymphocytes in the mechanism by which estrogen and PTH regulate HSCs will increase the scope and the depth of osteoimmunology, a novel field of multidisciplinary research. PUBLIC HEALTH RELEVANCE: New discoveries about the mechanism of action of estrogen and parathyroid hormone are relevant to public health as it may lead to the identification of novel strategies for improving the outcome of HSC transplantation in humans and for understanding the impact of menopause and hyperparathyroidism on hemopoiesis.