Cell Transitions during Bone Fracture Healing

骨折愈合过程中的细胞转变

• 批准号: 10754205
• 负责人: RALPH S MARCUCIO
• 金额: $ 58.14万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-18 至 2028-08-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10754205
• 关键词: Ablation; Abnormal Cell; Adopted; Adult; Animals; Binding; Bone Injury; Bone callus; Cartilage; Cell Compartmentation; Cell Differentiation process; Cell Lineage; Cell physiology; Cells; Cephalic; ChIP-seq; Chondrocytes; Cre lox recombination system; Data; Embryo; Environment; Event; FRAP1 gene; Failure; Fibrosis; Fracture; Genomics; Individual; Injury; Knockout Mice; Label; Maintenance; Mechanics; Mediating; Metaplasia; Methods; Molecular; Mus; NF1 gene; Natural regeneration; Neural Crest Cell; Osteoblasts; Outcome; Pathway interactions; Periosteal Cell; Periosteum; Phase; Physiologic Ossification; Play; Population; Process; Proto-Oncogene Proteins c-akt; Publishing; Role; Running; Series; Signal Transduction; Sirolimus; Site; Systems Biology; Testing; Tissues; Transcriptional Activation; Work; bone; bone fracture repair; cell type; directed differentiation; experimental study; healing; inducible Cre; injury and repair; intramembranous bone formation; loss of function; mTOR Inhibitor; mutant; osteoblast differentiation; osteochondral tissue; osteogenic; paligenosis; programs; reconstitution; recruit; response; stem cell differentiation; stem cell division; stem cell self renewal; stem cells; stem-like cell; transcription factor; wound

Summary Our understanding of cell lineages is currently being challenged. Cell plasticity appears to be more prevalent than previously thought and cell fate switching, even among fully differentiated cells is being more fully uncovered and understood. For example, ‘paligenosis’ is an emerging concept whereby fully differentiated cells revert to a stem cell like state and give rise to a multitude of cell types in part due to mTOR signaling. These observations have important implications for bone fracture healing. Multiple differentiation events occur for the bone to heal. Initially, the mechanical environment directs cell fate decisions within the periosteum. Mechanical stability directs differentiation of osteoblasts and intramembranous ossification, while instability directs differentiation of chondrocytes and endochondral ossification. Concomitantly, the stem cell compartment is maintained, and a renewed stem cell pool will eventually populate the periosteum that covers the new bone. At later stages of endochondral ossification chondrocytes become osteoblasts as the cartilage transforms into bone. Disruptions to these distinct events can lead to delayed or failed healing, which is often associated with increased fibrosis of the fracture site. In this application we propose to examine the process of differentiation of periosteal cells in response to the mechanical environment (Aim1), to assess transformation of chondrocytes into osteoblasts (Aim 2), and maintenance of the stem cell pool and population of the newly formed periosteum by stem cells (Aim 3). This work utilizes a systems biology approach to examine molecular mechanisms that underlie these cell fate decisions, and in parallel a more standard hypothesis-based approach. We focus on the role of Nf1 and Sox2 during differentiation of periosteal cells and the transformation of chondrocytes into osteoblasts. Our preliminary data show that deletion of Nf1 from the developing periosteum leads to a fibrous non-union after fracture, and we focus on the role of mTOR in mediating these outcomes. Our data also show that Sox2 is necessary for endochondral ossification, and we test the requirement of Sox2 in hypertrophic chondrocytes for transformation to osteoblasts. Finally, we examine a role for Sox2 in maintaining the stem cell compartment in the periosteum using a set of loss-of-function experiments in serial fracture repair. In summary, combining a systems biology approach with hypothesis testing is a powerful way to develop deep understanding of the processes regulating cell differentiation during fracture healing.

概括 目前，我们对细胞谱系的理解正在受到挑战。细胞可塑性似乎更普遍 比以前的思想和细胞命运切换，即使在完全分化的细胞中，也更加完全 被发现和理解。例如，“ paligenisis”是一个新兴的概念，从而完全分化了细胞 恢复到像状态这样的干细胞，并引起多种细胞类型，部分原因是MTOR信号传导。这些 观察对骨折愈合具有重要意义。发生多个差异化事件 骨骼康复。最初，机械环境指导骨膜内的细胞脂肪决策。机械的 稳定性指导成骨细胞和膜内骨化的分化，而不稳定性则指导 软骨细胞和内软骨骨化的分化。同时，干细胞室是 维持，一个新的干细胞池最终将填充覆盖新骨骼的骨膜。 当软骨转化为内侧软骨软骨细胞的后期阶段，软骨细胞变成成骨细胞 骨。对这些不同事件的破坏可能导致延迟或失败的康复，这通常与 骨折部位的纤维化增加。在此应用中，我们建议检查 骨膜细胞响应机械环境（AIM1），以评估软骨细胞的转化 进入成骨细胞（AIM 2），并维护新形成的perosteum的干细胞池和种群 由干细胞（AIM 3）。这项工作利用系统生物学方法来检查分子机制 这些细胞命运的决定是基于更标准假设的方法。我们专注于 NF1和Sox2在骨膜细胞分化中的作用以及软骨细胞转化为 成骨细胞。我们的初步数据表明，从发育的骨膜中删除NF1会导致纤维 骨折后的非工会，我们专注于MTOR在介导这些结果中的作用。我们的数据也显示 Sox2对于内软骨骨化是必需的，我们测试了肥厚型SOX2的需求 软骨细胞转化为成骨细胞。最后，我们研究了Sox2在维持干细胞中的作用 使用一组串行断裂修复中的功能丧失实验，在perosteum中的隔室。总之， 将系统生物学方法与假设检验相结合是发展深度的有力方法 理解裂缝愈合过程中细胞分化的过程。