Cell Transitions during Bone Fracture Healing

骨折愈合过程中的细胞转变

基本信息

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
项目类别：
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

项目摘要

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.

概括我们对细胞谱系的理解目前正受到挑战。细胞可塑性似乎更为普遍。细胞命运的转变比想象的要早，甚至在完全分化的细胞之间也正在更充分地发生例如，“异体分化”是一个新兴概念，其中细胞完全分化。恢复到干细胞样状态并产生多种细胞类型，部分原因是 mTOR 信号传导。观察结果对骨折愈合具有重要意义。最初，机械环境决定骨膜内的细胞命运。稳定性指导成骨细胞的分化和膜内骨化，而不稳定则指导成骨细胞的分化和膜内骨化。软骨细胞的分化和软骨内骨化同时进行。维持，更新的干细胞库最终将填充覆盖新骨的骨膜。软骨内骨化的后期阶段，随着软骨转变为成骨细胞，软骨细胞变成成骨细胞这些不同事件的破坏可能导致愈合延迟或失败，这通常与骨愈合有关。骨折部位纤维化增加在本申请中，我们建议检查骨折部位的分化过程。骨膜细胞对机械环境的反应（目标1），以评估软骨细胞的转化成骨细胞（目标 2），并维持干细胞库和新形成的骨膜群干细胞（目标 3）利用系统生物学方法来检查分子机制。这些细胞命运决定的基础，同时我们关注的是更标准的基于假设的方法。 Nf1 和 Sox2 在骨膜细胞分化和软骨细胞转化过程中的作用我们的初步数据表明，从发育中的骨膜中删除 Nf1 会导致纤维化。骨折后骨不连，我们的数据也显示了 mTOR 在调节这些结果中的作用。 Sox2 对于软骨内骨化是必需的，我们测试了肥厚性中 Sox2 的需要最后，我们研究了 Sox2 在维持干细胞中的作用。在连续骨折修复中使用一组功能丧失实验来确定骨膜室的功能。将系统生物学方法与假设检验相结合是开发深度学习的有效方法了解骨折愈合过程中调节细胞分化的过程。