The impact of host hypoxic signaling on antibacterial immunity and bone repair during Staphylococcus aureus osteomyelitis

项目摘要/摘要 骨髓炎是一种最常见的由革兰氏阳性细菌引起的骨骼炎症状态 金黄色葡萄球菌。金黄色葡萄球菌感染骨骼是一种常见且高度病态的疾病。在.期间 骨髓炎，骨骼的结构基质和血管构筑被破坏，导致 坏死性无血管组织会增加慢性感染的风险。在骨髓炎期间会发生极度缺氧 由于血管供应改变，炎症渗透，以及侵袭性金黄色葡萄球菌的新陈代谢。东道主 通过启动低氧诱导因子(HIF)信号来响应低氧。HIF信号转而调制 骨骼重塑。除了骨骼的动态平衡和修复外，HIF信号还参与调节 抗菌免疫。然而，低氧和HIF信号在骨髓炎中的作用尚不清楚。 可作为优化免疫反应对抗侵袭的重要临床靶点。 感染。我们已经建立了一种强大的小鼠骨髓炎模型，该模型概括了骨髓炎的发病机制 人类疾病。使用这个模型，我们证明了极端低氧存在于感染灶上。 独立于非感染性骨折愈合的方式。我们的初步数据表明，血管内皮生长因子，一口井- HIF信号的特征性靶点在骨髓炎期间相对于模拟感染的骨增加， 这与HIF信号在骨的侵袭性感染过程中被激活的观点一致。在常压下，我们 还观察到成骨细胞(骨构建细胞)在体外对金黄色葡萄球菌的刺激反应 增加调控HIF信号、控制宿主介导的骨重建的基因的转录，以及 调节先天免疫反应。这一提议的首要假设是组织氧合和 金黄色葡萄球菌宿主低氧信号反应对抗菌免疫和骨修复的影响 骨髓炎。我将用两个综合的具体目标来检验这一假设。在具体目标1中，我将定义 氧合作用在介导成骨细胞先天免疫反应和骨稳态中的作用 体外金色刺激物。在特定的目标2中，我将确定HIF信号对抗菌的影响 金黄色葡萄球菌骨髓炎时的免疫和骨重建。在Aim 2的实验中，我将在 活体分析将利用小鼠遗传学和生物材料科学来改变HIF信号在 并研究缺氧诱导因子对免疫反应和骨修复的影响。把这些研究放在一起 将1)确定氧合作用在决定先天免疫和骨重建反应中的作用 成骨细胞，2)确定成骨细胞HIF信号对抗菌免疫和骨修复的影响 3)测试HIF靶向治疗作为抗感染佐剂的潜力。 侵袭性骨感染。总的来说，这项提议将阐明氧合作用如何影响骨骼细胞。 生物学和对细菌病原体的先天免疫反应，同时提供理想的培训和指导 以发展我未来的职业生涯，成为一名独立的调查员和内科科学家。

PROJECT SUMMARY/ABSTRACT Osteomyelitis is an inflammatory state of bone most commonly triggered by the Gram-positive bacterium Staphylococcus aureus. Staphylococcal infection of bone is both common and highly morbid. During osteomyelitis, the structural matrix and vascular architecture of bone is destroyed, resulting in regions of necrotic, avascular tissue that increase risk of chronic infection. Extreme hypoxia occurs during osteomyelitis due to an altered vascular supply, inflammatory infiltration, and the metabolism of invasive S. aureus. The host responds to hypoxia by initiating hypoxia-inducible factor (HIF) signaling. HIF signaling, in turn, modulates bone remodeling. Beyond bone homeostasis and repair, HIF signaling is implicated in the regulation of antibacterial immunity. However, the role of hypoxia and HIF signaling during osteomyelitis is unknown and may serve as an important clinical target for optimizing immune responses to combat invasive infection. We have developed a powerful murine model of osteomyelitis that recapitulates the pathogenesis of human disease. Using this model, we demonstrated that extreme hypoxia is present at the infectious focus in a manner independent of non-infectious fracture healing. Our preliminary data demonstrate that VEGF, a well- characterized target of HIF signaling, is increased during osteomyelitis relative to mock-infected bone, consistent with the notion that HIF signaling is activated during invasive infection of bone. Under normoxia, we also observed that osteoblasts (bone-building cells) sense and respond to S. aureus stimulation in vitro by increasing the transcription of genes that regulate HIF signaling, control host-mediated bone remodeling, and mediate innate immune responses. The overarching hypothesis of this proposal is that tissue oxygenation and host hypoxic signaling responses influence antibacterial immunity and bone repair during S. aureus osteomyelitis. I will test this hypothesis with two integrated Specific Aims. In Specific Aim 1, I will define the role of oxygenation in mediating osteoblast innate immune responses and bone homeostasis in response to S. aureus stimulation in vitro. In Specific Aim 2, I will determine the impact of HIF signaling on antibacterial immunity and bone remodeling during S. aureus osteomyelitis. Within the experiments of Aim 2, I will use in vivo analyses that will harness both mouse genetics and biomaterial science to alter HIF signaling during osteomyelitis and investigate the impact of HIF on immune responses and bone repair. Together these studies will 1) define the role of oxygenation in dictating the innate immune and bone remodeling responses of osteoblasts, 2) define the impact of osteoblast HIF signaling on antibacterial immunity and bone repair during S. aureus osteomyelitis, and 3) test the potential of HIF-targeted therapies as an anti-infective adjuvant for invasive infection of bone. Collectively, this proposal will elucidate how oxygenation impacts skeletal cell biology and the innate immune responses to bacterial pathogens while providing ideal training and mentorship to develop my future career as an independent investigator and physician-scientist.