Role of Complement in Commensal Microbiota Actions Regulating Sketal Maturation

摘要 共生微生物群严格调节骨免疫过程介导青春期后骨骼 发展我们的研究表明小肠菌群抑制成骨细胞骨- 形成细胞，并增强骨吸收细胞，这会损害骨量增加。然而，在这方面， 在整个生命周期中辨别骨骼微生物群对骨骼的影响的机制尚不清楚。 骨免疫学的研究表明，骨髓中的免疫细胞调节骨 建模/重塑。尽管知道肠道微生物群引导与宿主的串扰， 免疫，阐明肠道微生物群免疫调节作用的免疫机制研究 骨骼成熟尚不清楚。研究人员博士后研究工作的初步结果表明， 肠道微生物-宿主相互作用刺激补体信号传导， 健康和疾病中的成熟骨骼。 补体信号传导保护宿主免受感染并调节免疫应答， 补体在维持体内微生物群平衡中的作用。我们 初步数据表明，肠道微生物群上调循环补体， 过敏毒素C3 a，其也与炎症性肠发病机制有关。补体受体 C3 aR在成骨细胞和破骨细胞上都有表达，这意味着C3 a可能是成骨细胞和破骨细胞的关键调节因子。 肠道微生物群对健康和疾病中骨骼成熟的影响。三个具体目标将解决 在成骨细胞和破骨细胞中使用C3 aR缺失的转基因小鼠进行的关键体内和体外研究， 健康和下葡聚糖硫酸钠（DSS）诱导的结肠炎。这三个目标将调查的整体 C3 a的肠道微生物群上调调节C3 aR衍生的骨骼成熟的假设 在健康和疾病的整个生命周期。目的1将阐明肠道微生物群在 正常和炎症条件下骨骼成熟和退化中C3 aR介导的成骨细胞生成 肠道状况目的2将检查在C3 aR-破骨细胞生成信号传导中的小肠肠道微生物群作用， 在健康和疾病中的成熟和衰老的骨骼。目标3将决定是否给予益生菌 在青春期后骨骼发育过程中调节C3 a/C3 aR信号传导。阐明以下方面的关系： C3/C3 aR信号传导、肠道微生物群和骨骼将为治疗干预提供机会， 优化年轻军人的骨量增加，防止骨骼老化 老兵 这项研究旨在确定骨免疫学过程调节峰值骨量增加， 承受年龄相关和/或疾病相关的骨骼退化。这些研究将创新性地使用 骨细胞特异性C3 aR敲低模型，以确定微生物群衍生的补体信号传导对 骨骼成熟值得注意的是，这项工作提出了在峰值骨量增加窗口期间益生菌干预 为了确定骨骼微生物群对整个骨骼上补体C3 a/C3 aR的作用， 寿命此外，该提案将在新的专业知识和职业领域提供坚实的职业发展 申请人过渡到独立VA调查员所需的工具。这将是完成 通过CDA提供的拟议课程、实践培训、网络和指导经验， 2机制。

Abstract Commensal microbiota critically regulates osteoimmune processes mediating post-pubertal skeletal development. Our studies have shown that the commensal gut microbiota suppresses osteoblastic bone- forming cells and enhances osteoclastic bone-resorbing cells, which impairs bone mass accrual. However, mechanisms discerning commensal microbiota effects on bone across the lifespan are unclear. The study of osteoimmunology has shown that immune cells in the bone marrow regulate bone modeling/remodeling. Despite knowledge that the commensal gut microbiota directs crosstalk with host immunity, immune mechanistic studies elucidating the commensal gut microbiota immunomodulatory effects on skeletal maturation are unclear. Preliminary findings from the investigator’s postdoctoral research work suggest that commensal microbiota-host interactions stimulate complement signaling to have system catabolic effects in the maturing skeleton in health and disease. Complement signaling protects the host from infection and modulates the immune response, highlighting the role of complement in maintaining a homeostatic relationship with the commensal microbiota. Our preliminary data demonstrated that the commensal microbiota upregulates circulating complement anaphylatoxin C3a, which has also been implicated in inflammatory bowel pathogenesis. Complement receptor C3aR is expressed on both osteoblasts and osteoclasts, implying that C3a may be a critical regulator of commensal microbiota effects on the maturing skeleton in health and disease. Three specific aims will address critical in vivo and in vitro studies utilizing transgenic mice deleting C3aR in both osteoblasts and osteoclasts in health and under dextran sodium sulfate (DSS)-induced colitis. These three aims will investigate the overall hypothesis that the commensal gut microbiota upregulation of C3a regulates C3aR derived skeletal maturation in health and disease throughout the lifespan. Aim 1 will elucidate the role of commensal gut microbiota on C3aR-mediated osteoblastogenesis in skeletal maturation and deterioration under normal and inflammatory bowel conditions. Aim 2 will examine commensal gut microbiota actions on C3aR-osteoclastogenic signaling in the maturing and aging skeleton in health and disease. Aim 3 will determine whether probiotic administration regulates C3a/C3aR signaling during post-pubertal skeletal development. Elucidating the relationship between C3/C3aR signaling, the gut microbiota, and bone will provide opportunities for therapeutic interventions to optimize bone mass accrual in young service members and protect against skeletal deterioration in aging Veterans. This research seeks to define osteoimmunological processes regulating peak bone mass accrual to withstand either age-related and/or disease-related skeletal deterioration. These studies will innovatively use bone cells specific C3aR knockdown models to determine microbiota derived complement signaling effects on skeletal maturation. Notably, this work proposes probiotic interventions during a peak bone mass accrual window to define the role of the commensal microbiota on complement C3a/C3aR on the skeleton throughout the lifespan. Additionally, this proposal will provide solid career development in new areas of expertise and career tools necessary for the applicant's transition to an independent VA investigator. This will be accomplished through proposed coursework, hands-on training, networking, and mentoring experiences provided by the CDA- 2 mechanism.