Complement and Osteoporosis

描述(申请人提供)：我们实验室的最新结果揭示了补体系统和绝经后骨质丢失之间的一种新的、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成分的小鼠在卵巢切除(OVX)后可以防止骨质丢失，这是通过微型计算机断层扫描(MicroCT)分析显示的。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降低。此外，抑制补体信号抑制了人破骨细胞从造血祖细胞分化而来。根据这些结果，我们推测补体系统是骨平衡的关键调节因素，也是治疗骨质疏松症的潜在靶点。为了解决这一假设，本文提出了两个目标。目的1通过评估几种OVXed补体基因敲除小鼠(因子D-/-、C1q-/-、MBL-/-、C3-/-、C3aR-/-、C5aR-/-和C3aR-/-C5aR-/-)和野生型(WT)对照组的骨结构，研究补体激活途径以及补体和补体受体缺陷对体内骨转换的影响；MicroCT和骨组织形态计量学将是主要的读数。目的1还将通过间充质干细胞(MSC)在多孔陶瓷载体中形成异位骨的交叉植入研究，研究局部补体产生在骨平衡调节中的作用。目的2将在WT小鼠和人源化小鼠身上测试补体受体抑制剂作为预防骨质疏松症的方法的使用。WT(C57BL/6)小鼠、人脐血干细胞移植NSG(NOD.Cg-Prkdccid Il2rgtm1Wjl/SzJ)小鼠、人MSC移植NSG小鼠、人脐血干细胞和MSC移植NSG小鼠将被OVXT、治疗，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基因敲除小鼠分离的MSCs异位形成的骨，然后将反之亦然，然后分析组织形态计量学骨参数-这使得能够确定MSCs局部补体缺乏对骨形成和丢失的作用，并探讨当WT MSCs被移植到补体基因敲除小鼠中时，造血细胞中补体缺乏的影响。在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意义的，并将探讨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引起的骨丢失中，补体信号减弱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，这有可能使补体成为开发新的、有效的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.