Conditional Deletion of Irf8 in Monocyte Macrophage Lineage Provides Novel Insight into Irf8s Important Function in Osteoclast Regulation and Bone Metabolism

项目总结/摘要 牙周炎、骨质疏松症、类风湿性关节炎等疾病的特征是骨质过多 由于破骨细胞活性增加而导致骨吸收。据估计，骨质疏松症影响约10万美国人 还有1900万人处于危险之中牙周炎影响约46%的美国30岁以上的成年人。类风湿性关节炎 影响约5440万美国成年人-相当于约25%的人口。这些疾病的影响 对个人、社区和卫生服务造成的社会、心理和经济负担是巨大的。 尽管存在这些问题，但这些细胞中导致破骨细胞功能失调的分子机制仍有待进一步研究。 病理状况仍不清楚，在制定有针对性的干预措施方面存在严重的知识差距 和治疗策略。我们的长期目标是识别和深入了解积极的 和破骨细胞分化的负调节因子，并利用所获得的知识开发新的 破骨细胞介导的疾病的干预和治疗方法。为了实现我们的长期 为了达到这一目的，我们在干扰素调节因子8（IRF 8）基因中发现了一种新的突变， 破骨细胞活性增加，容易患上一种称为“多发性特发性宫颈炎”的罕见牙周疾病 根吸收（MICRR）。目前的建议采取了一个新的方向，以深入了解IRF 8 在破骨细胞调节和牙周稳态中的作用。到目前为止，IRF 8在破骨细胞生成中的作用已经被证实。 使用Irf 8 gKO小鼠研究。然而，造血干细胞的数量和性质的严重改变， Irf 8 gKO小鼠中的IRF 8细胞已经影响了对IRF 8在来自于 单核细胞/巨噬细胞谱系。为了克服这一限制，我们已经产生了骨髓细胞特异性Irf 8， 条件性敲除（cKO）。在本申请中，我们将应用遗传方法，并使用体外细胞培养 系统和Irf 8 cKO小鼠模型来研究：1）IRF 8在单核细胞亚群发育中的重要性（2） 不同单核细胞亚群的破骨细胞生成潜力及其如何受IRF 8影响，以及（3）特异性 单核细胞亚群对牙周炎组织破坏的作用我们将通过一个 Irf 8 cKO小鼠模型与下一代测序、流式细胞术 细胞计数和显微CT这项研究具有重要意义，因为它将提供关键的机制， 深入了解控制破骨细胞分化的转录因子复杂网络的调节。 这项工作将开发基础资源，供其他研究人员用于研究各种骨骼 在IRF 8中具有已知风险等位基因的疾病和炎性疾病。最重要的是，结果将奠定 为各种破骨细胞介导的骨疾病开发更好的治疗方案奠定了基础，包括 牙周病

PROJECT SUMMARY/ABSTRACT Diseases such as periodontitis, osteoporosis, and rheumatoid arthritis, are characterized by excessive bone resorption due to increased osteoclast activity. It is estimated that osteoporosis affects ~10 million Americans with another 19 million at risk. Periodontitis affects ~46% of the U.S. adults aged ³30 years. Rheumatoid arthritis affects ~54.4 million U.S. adults - equating to about 25% of the population. The impact of these diseases in terms of social, psychological, and economic burden on individuals, communities, and health services is enormous. Despite these concerns, the molecular mechanisms contributing to dysregulated osteoclast function in these pathological conditions remain unclear, creating a critical knowledge gap in developing targeted interventions and therapeutic strategies. Our long-term goal is to identify and gain an in-depth understanding of the positive and negative regulators of osteoclast differentiation and utilize the gained knowledge to develop new interventional and therapeutic approaches for osteoclast-mediated disorders. Towards achieving our long-term goal, we have identified a novel mutation in the Interferon Regulatory Factor 8 (IRF8) gene that promotes increased osteoclast activity and susceptibility to a rare periodontal disease termed “Multiple Idiopathic Cervical Root Resorption (MICRR). The current proposal takes a new direction to gain in-depth knowledge about IRF8 role in osteoclast regulation and periodontal homeostasis. To date, IRF8’s role in osteoclastogenesis has been studied using Irf8 gKO mice. However, the severely altered population and properties of hematopoietic stem cells in Irf8 gKO mice has affected the detailed analysis of IRF8 function in osteoclast precursors derived from a monocyte/macrophage lineage. To overcome this limitation, we have generated a myeloid cell-specific Irf8 conditional knockout (cKO). In this application, we will apply genetic approaches and use both in vitro cell culture systems and Irf8 cKO mouse model to investigate: 1) Importance of IRF8 in monocyte subset development (2) Osteoclastogenic potential of different monocyte subsets and how it is influenced by IRF8, and (3) Specific monocyte subsets contributing to tissue destruction in periodontitis. We will pursue these aims using an innovative combination of Irf8 cKO mouse model and techniques such next-generation sequencing, flow cytometry, and micro-CT. The proposed research is significant, because it will provide critical mechanistic insights into the regulation of complex networks of transcription factors that govern osteoclast differentiation. This work will develop foundational resources that will be used by other researchers for studying various bone disorders and inflammatory disorders that have known risk alleles in IRF8. Most importantly, the results will lay the groundwork to develop better treatment options for various osteoclast-mediated bone disorders, including periodontal disease.