Bone Pseudoarthrosis Dissected through the Generation of New Mouse Models

项目总结 骨假关节是骨愈合过程中的一种衰弱缺陷。骨折和假关节都有 代表了一种潜在的、局限性的先天性骨骼组织紊乱的副现象，这种疾病改变了 骨骼生长和重塑的过程，并危及两者的机械健全的发展 内部结构和骨修复的过程。假性关节病的发病机制尚不明确 用于建立适应疗法。骨愈合涉及四种主要细胞类型：间充质干细胞 细胞(MSCs)、软骨细胞、成骨细胞和破骨细胞。到目前为止，有证据表明骨骼中缺乏NF1 形成细胞是NF1(神经纤维瘤病)假关节的罪魁祸首，但涉及的细胞类型仍然 身份不明。今天的挑战是确定NF1中功能受损的细胞类型 假关节，以表征与该细胞类型中NF1功能丧失相关的缺陷，并基于 在此基础上提出相应的纠正这些缺陷的策略。在这项提案中，我们问的是 NF1功能缺失或NF1功能丧失在三种特定的骨细胞类型中，软骨细胞， 成骨细胞或其共同前体MSCs会损害骨愈合。为了解决这个问题，我们 建议使用NF1+/-小鼠和缺乏一个或两个NF1拷贝的条件性小鼠模型 骨修复研究中的骨髓间充质干细胞、软骨细胞或成骨细胞。有了这些鼠标模型，就有可能 通过以下方法确定软骨骨痂的形成是否需要一份或两份NF1 软骨细胞或骨折后成骨细胞对骨痂的钙化和重塑(特异性 目标一和目标二)。我们还设计了旨在描述一种新的治疗方法的研究。 骨假关节，基于我们以前的工作(R21AR053978-01)和ERK抑制特性 PD19830和洛伐他汀用于纠正NF1-/-成骨细胞的缺陷(特定目标III)。 在本申请中提出的研究旨在表征新的调控骨骼的途径和基因 重塑和修复，长期目标是更好地了解骨骼疾病并提出 经过调整的疗法。我们期望我们的研究1)表征NF1在骨修复的特定阶段中的作用 特定的骨细胞类型，2)表征新的治疗靶点和策略，以确定最 对这种综合征进行适当的治疗，以及3)提供可用于临床前的新的小鼠模型 工具。

PROJECT SUMMARY Bone pseudoarthrosis is a debilitating defect of bone healing. Both fracture and pseudoarthrosis represent the epiphenomena of an underlying, localized congenital disorder of skeletal tissues that alters the process of bone growth and remodeling and jeopardizes both the development of a mechanically sound internal structure and the process of bone repair. The etiopathology of pseudoarthrosis remains to be defined for the establishment of adapted therapies. Bone healing involves four main cell types: mesenchymal stem cells (MSCs), chondrocytes, osteoblasts and osteoclasts. To date, evidence suggests that lack of Nf1 in bone forming cells is responsible for NF1 (neurofibromatosis) pseudoarthrosis, but the cell types involved remain unidentified. The challenges today are to identify the cell types whose function is impaired in NF1 pseudoarthrosis, to characterize the defects associated with loss of function of Nf1 in this cell type, and based on this knowledge to propose adapted strategies to correct these defects. In this proposal, we ask whether Nf1 haplo-insufficiency or Nf1 loss of function in three specific bone cell types, chondrocytes, osteoblasts or their common precursor, MSCs, impairs bone healing. To address this question, we propose to use Nf1+/- mice and conditional mouse models lacking one or both copies of Nf1 specifically in MSCs, chondrocytes or osteoblasts in bone repair studies. With these mouse models in hand, it will possible to determine whether one or two copies of Nf1 is required for the formation of a cartilaginous callus by chondrocytes or for the calcification and remodeling of this callus by osteoblasts following fracture (Specific Aim I and II). We also designed studies aimed at characterizing a new therapeutic approach for treating bone pseudoarthrosis, based on our previous work (R21AR053978-01) and the ERK inhibitory property of PD19830 and lovastatin to correct the defects of Nf1-/- osteoblasts (Specific Aim III). The studies proposed in this application aim at characterizing novel pathways and genes regulating bone remodeling and repair, with the long-term goals of better understanding skeleton diseases and proposing adapted therapies. We expect our studies 1) to characterize the role of Nf1 at specific stages of bone repair in specific bone cell types, 2) to characterize novel therapeutic targets and strategies to identify the most appropriate treatment for this syndrome and 3) to provide new mouse models that can be used as pre-clinical tools.