Complement and Osteoporosis

描述（由申请人提供）：我们实验室的最新结果揭示了补体系统与绝经后骨质流失之间新的和意想不到的关系，这有可能导致骨质疏松症的新疗法。这些研究表明，缺乏补体系统C3组分的小鼠在卵巢切除术（OVX）后受到保护，免受骨质流失，如显微计算机断层扫描（microCT）分析所示。我们的体外研究表明，补体受体缺陷小鼠的骨髓细胞分化为功能性破骨细胞的能力下降。此外，补体信号传导的抑制抑制了人破骨细胞从造血祖细胞的分化。基于这些结果，假设补体系统是骨平衡的关键调节因子，也是治疗骨质疏松症的潜在靶点。为了解决这一假设，提出了两个目标。目的1将通过评估几种去卵巢补体基因敲除小鼠的骨结构来研究补体激活途径，以及补体和补体受体缺乏如何影响体内骨转换（因子D-/-、C1 q-/-、MBL-/-、C3-/-、C3 aR-/-、C5 aR-/-和C3 aR-/-C5 aR-/-）和野生型（WT）对照; microCT和骨组织形态计量学将是主要的读数。目的1还将检查局部补体产生的作用，在骨平衡的调节中使用交叉植入研究，其中间充质干细胞（MSC）形成异位骨在多孔陶瓷载体。目的2将测试补体受体抑制剂作为在WT小鼠和人源化小鼠中预防骨质疏松症的手段的用途。WT（C57 BL/6）小鼠、人脐带血干细胞植入的NSG（NOD.Cg-Prkdcscid Il 2 rgtm 1 Wjl/SzJ）小鼠、人MSC植入的NSG小鼠以及人脐带血干细胞和MSC植入的NSG小鼠将进行OVX、处理并通过microCT和骨组织形态计量学进行评估。Aim 1研究的一个新方面是使用从敲除小鼠分离的MSC异位形成的骨，然后将其植入WT小鼠，反之亦然，然后测定其组织形态计量骨参数-这允许确定MSC的局部补体缺乏对骨形成和损失的作用，并且还探讨了当WT MSC植入补体敲除小鼠时，造血细胞中补体缺陷的影响。Aim 2中使用WT小鼠和不同人源化小鼠的补体受体拮抗剂治疗实验是最具临床相关性的，并且将解决使用这些抑制剂治疗或预防人类骨质疏松症的潜力。这些研究将阐明在雌激素缺乏诱导的骨丢失中，补体信号减少如何影响成骨细胞和破骨细胞的分化。这些研究的长期目标是开发治疗或预防骨质疏松症的新疗法。 公共卫生相关性：该项目将研究补体在骨质疏松症中调节骨转换的作用，这有可能开辟补体作为开发新的有效治疗骨质疏松症的新靶点。

DESCRIPTION (provided by applicant): Recent results in our laboratories have revealed a new and unexpected relationship between the complement system and post-menopausal bone loss, which has the potential to lead to new therapies for osteoporosis. These studies revealed that mice lacking the C3 component of the complement system were protected from bone loss after ovariectomy (OVX), as shown by micro-computed tomography (microCT) analysis. Our in vitro studies revealed that bone marrow cells from complement receptor-deficient mice had decreased capacity to differentiate into functional osteoclasts. Further, inhibition of complement signaling suppressed human osteoclast differentiation from hematopoietic progenitors. Based on these results, it is hypothesized that the complement system is a key regulator of bone balance and a potential target for the treatment of osteoporosis. To address this hypothesis, two Aims are proposed. Aim 1 will examine which complement activation pathway is involved, and how complement and complement receptor deficiency impact in vivo bone turnover by assessing bone structure in several OVXed complement knockout mice (Factor D-/-, C1q-/-, MBL-/-, C3-/-, C3aR-/- ,C5aR-/-, and C3aR-/-C5aR-/-) and wild type (WT) controls; microCT and bone histomorphometry will be the primary readouts. Aim 1 also will examine the role of local complement production in the regulation of bone balance using cross-implantation studies where mesenchymal stem cells (MSC) form ectopic bone in porous ceramic carriers. Aim 2 will test the use of complement receptor inhibitors as a means of preventing osteoporosis both in WT mice and humanized mice. WT (C57BL/6) mice, human umbilical cord blood stem cell-implanted NSG (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ) mice, human MSC-implanted NSG mice, and both human umbilical cord blood stem cell and MSC-implanted NSG mice will be OVXed, treated, and assessed by microCT and bone histomorphometry. A novel aspect of the Aim 1 studies is the use of ectopically formed bone from MSCs isolated from the knockout mice that are then implanted into WT mice, and vice versa, which are then assayed for histomorphometric bone parameters - this allows for determination of the role of local complement deficiency of the MSCs on bone formation and loss, and also probes the effect of complement deficiency in hematopoietic cells when WT MSCs are implanted into the complement knockout mice. The complement receptor antagonists treatment experiments in Aim 2 using WT mice and different humanized mice are the most clinically relevant, and will address the potential of using these inhibitors for treating or preventing osteoporosis in humans. These studies will clarify how diminished complement signaling affects osteoblast and osteoclast differentiation in estrogen deprivation induced bone loss. The long-term goal of these studies is to develop new therapies to treat or prevent osteoporosis. PUBLIC HEALTH RELEVANCE: This project will study the role of complement in regulating bone turnover in osteoporosis, which has the potential of opening up complement as a new target for developing novel, effective therapies against osteoporosis.