Spatial and Temporal Role of the Runx3 Transcription Factor in Secondary Fracture Healing

Runx3 转录因子在二次骨折愈合中的时空作用

• 批准号: 10618866
• 负责人: HICHAM M DRISSI
• 金额: --
• 依托单位: VETERANS HEALTH ADMINISTRATION
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-04-01 至 2024-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10618866
• 关键词: Acceleration; Age; Aging; Biomechanics; Blood Vessels; Blood capillaries; Bone Tissue; Bone callus; Cartilage; Cell Differentiation process; Cell Lineage; Cells; Chondrocytes; Clinical; Data; Diabetes Mellitus; Economic Burden; Encapsulated; Evaluation; Event; Femoral Fractures; Flow Cytometry; Fracture; Frequencies; Gelatin; Healthcare Systems; Histologic; Histology; Hydrogels; Image; Impairment; Incidence; Invaded; Knockout Mice; LoxP-flanked allele; Mediating; Mesenchymal; MicroRNAs; Modality; Modeling; Molecular; Molecular Analysis; Molecular Target; Monitor; Mus; Names; Osteoblasts; Osteocytes; Osteogenesis; Osteoporosis; Osteoporotic; Pathway interactions; Patients; Periosteal Cell; Periosteum; Pharmaceutical Preparations; Population; Process; RNA; RUNX3 gene; Regulator Genes; Regulatory Pathway; Reporter; Reporting; Repression; Roentgen Rays; Role; Site; Smoking; Sorting; Tamoxifen; Testing; Time; Tissues; Torsion; Transgenic Mice; Translational Research; Vascular blood supply; Veterans; Visualization; Work; angiogenesis; bone; bone fracture repair; bone healing; bone imaging; bone mass; bone repair; cartilaginous; clinically relevant; comorbidity; comparison control; conditional knockout; efficacy evaluation; experimental study; healing; ineffective therapies; laser capture microdissection; long bone; lost work time; microCT; microRNA delivery; multiphoton microscopy; nanofiber; new therapeutic target; novel; novel therapeutic intervention; novel therapeutics; osteogenic; osteoporosis with pathological fracture; pre-clinical; prevent; progenitor; skeletal stem cell; stem cells; success; transcription factor; two photon microscopy

Clinical Dilemma: The frequency of impaired fracture healing is increased with aging as well as in the presence of other patient-related factors such as smoking, osteoporosis, and diabetes. Treatment of fractures in this setting continues to pose a significant economic burden on the US healthcare system due to increases in time lost from work as well as increases in the expenses associated with fracture-associated complications. While various bone anabolic drugs are successful in increasing homeostatic bone mass in osteoporotic patients and decreasing fracture incidence, they have not demonstrated significant success in enhancing fracture repair. Therefore, identifying novel molecular targets to accelerate secondary fracture healing in this very common setting remains of paramount importance. Relevance to the VA: According to the Office of VA Inspector General report in 2010, osteoporotic patients who suffered a single fracture present a higher incidence of subsequent fractures (20-fold increase) than unaffected populations. Impaired or delayed bony union following fracture of long bones prevents or delays a significant percentage of VA patients from resuming their daily activities and returning to work. Ineffective treatment of these fractures maximizes the economic burden on the VA healthcare system. Identifying novel molecular targets to enhance secondary bone repair remains of paramount importance. The objective of this translational research application is to enhance secondary fracture healing by targeting novel regulatory pathways that enhance periosteal cell-induced osteogenesis and angiogenesis during fracture callus formation. Scientific premise: We provide compelling preliminary evidence of the following: 1. Runx3 is expressed in chondrocytes, osteoblasts and osteocytes of C57BL6j murine long bones. 2. Runx3 expression levels are increased in soft cartilaginous calluses and subsequently decreased in bony calluses of murine femoral fractures. 3. Conditional deletion of Runx3 in periosteal cells (cKO) resulted in enhanced secondary bone healing as evidenced by histological, histomorphometric, and molecular analyses. 4. The cellular mechanisms underlying these positive effects on secondary bone healing implicate increased osteogenesis as well as angiogenesis of fractured periosteal cells from Runx3 cKO compared to control mice. 5. Use of multiphoton microscopy demonstrate the feasibility of tracking Prx1+ skeletal progenitor cells during bone repair and longitudinally monitor the bone healing process for lineage tracing experiments. Here we hypothesize that Runx3 is a molecular switch that controls the transition from cartilaginous to bony callus, and its deletion in the chondrogenic cell lineage will accelerate secondary fracture healing. To verify this hypothesis, we propose to first establish the effects of stage-specific repression of Runx3 on secondary fracture healing (Aim 1). We will then determine the mechanisms via which Runx3 controls mesenchymal cell differentiation into the chondro/osteogenic lineages (Aim 2). Finally, we will assess the efficacy of Runx3 inhibition during fracture repair in control C57BL6 mice through controlled and sustained delivery of miRNA encapsulated hydrogel and examine the rate of bone healing and biomechanical strength of healed bone (Aim 3). Impact: Defining the pathways that governthe transition from soft to bony callus will help identify new therapies to accelerate secondary fracture healing. Here, we will establish Runx3 as a novel therapeutic target.

临床困境：随着衰老以及在 存在其他与患者有关的因素，例如吸烟，骨质疏松症和糖尿病。裂缝的治疗 在这种情况下，由于增加，在美国医疗保健系统上造成了巨大的经济负担 随着时间的流逝，与骨折相关并发症相关的费用损失以及增加的费用增加。 虽然各种骨合成代谢药物成功地增加了骨质疏松剂的稳态骨量 患者并降低骨折的发生率，他们在增强方面尚未显示出显着成功 断裂修复。因此，确定新的分子靶标在此加速次级断裂愈合 非常普遍的环境仍然是至关重要的。 与VA的相关性：根据VA Inspector General Report的2010年，骨质疏松患者 遭受单个骨折的人比随后的骨折发生率更高（增加20倍） 不受影响的人群。长骨骨折后受损或延迟的骨结合阻止或延迟 VA患者恢复日常活动并重返工作岗位的大量比例。无效 这些骨折的治疗最大化VA医疗保健系统的经济负担。识别小说 分子靶标，以增强次级骨修复至关重要。这个目的 转化研究应用程序是通过针对新的调节性来增强次级骨折愈合 增强骨膜细胞诱导的成骨和血管生成的途径。 科学前提：我们提供以下令人信服的初步证据： 1。Runx3在C57BL6J鼠长骨的软骨细胞，成骨细胞和骨细胞中表达。 2。软骨癌中的Runx3表达水平升高，随后在骨中降低 鼠股骨折的老茧。 3。骨膜细胞中Runx3的条件缺失（CKO）导致次级骨愈合的增强 组织学，组织形态计量学和分子分析证明了这一点。 4。这些对次级骨愈合的积极作用的基础的细胞机制牵涉到增加 与对照相比 老鼠。 5。多光子显微镜的使用证明了跟踪PRX1+骨骼祖细胞的可行性 骨修复并纵向监测骨修复过程，以进行谱系追踪实验。 在这里，我们假设Runx3是一个分子开关，可以控制从软骨到 骨愈伤组织及其在软骨细胞谱系中的缺失将加速次要断裂 康复。 为了验证这一假设，我们建议首先建立runx3对阶段特异性抑制的影响 次级断裂愈合（AIM 1）。然后，我们将确定Runx3控制的机制 间充质细胞分化为软骨/成骨谱系（AIM 2）。最后，我们将评估 RUNX3抑制在对照C57BL6小鼠中裂缝修复过程中通过受控和持续的功效 miRNA封装的水凝胶的递送，并检查骨愈合速率和生物力学强度的速度 治愈骨骼（目标3）。 影响：定义控制从软愈伤组织过渡到骨愈伤组织的途径将有助于识别新疗法 加速继发性骨折愈合。在这里，我们将建立RUNX3作为一种新颖的治疗靶点。