Bone Pseudoarthrosis Dissected through the Generation of New Mouse Models

描述（由申请人提供）： 骨假关节是一种骨愈合的缺陷。骨折和假关节都是骨骼组织潜在的、局部的先天性疾病的副现象，这种疾病改变了骨生长和重塑的过程，并危及机械健全的内部结构的发育和骨修复的过程。假关节的发病机制仍有待确定，以建立适应的治疗方法。骨愈合涉及四种主要的细胞类型：间充质干细胞（MSC），软骨细胞，成骨细胞和破骨细胞。迄今为止，有证据表明，骨形成细胞中Nf 1的缺乏是NF 1（神经纤维瘤病）假关节的原因，但涉及的细胞类型仍未确定。今天的挑战是确定的细胞类型，其功能受损的NF 1假关节，表征的缺陷与NF 1在这种细胞类型的功能丧失，并根据这些知识，提出适应的策略，以纠正这些缺陷。在这个建议中，我们问是否Nf 1单倍不足或Nf 1功能丧失三种特定的骨细胞类型，软骨细胞，成骨细胞或其共同的前体，MSC，损害骨愈合。为了解决这个问题，我们建议使用Nf 1小鼠和条件小鼠模型缺乏一个或两个副本的Nf 1特别是在骨髓间充质干细胞，软骨细胞或成骨细胞在骨修复研究。有了这些小鼠模型，就有可能确定Nf 1的一个或两个拷贝是软骨细胞形成软骨骨痂所必需的，还是骨折后成骨细胞钙化和重塑骨痂所必需的（具体目标I和II）。我们还设计了旨在表征骨假关节病新治疗方法的研究，基于我们之前的工作（R21 AR 053978 -01）以及PD 19830和洛伐他汀纠正Nf 1-/-成骨细胞缺陷的ERK抑制特性（特定目标III）。本申请中提出的研究旨在表征调节骨重建和修复的新途径和基因，其长期目标是更好地了解骨骼疾病并提出适应性疗法。我们希望我们的研究1）表征Nf 1在特定骨细胞类型中骨修复的特定阶段的作用，2）表征新的治疗靶点和策略，以确定最适合这种综合征的治疗方法，3）提供可用作临床前工具的新小鼠模型。 公共卫生相关性：本申请中提出的研究旨在通过产生新的小鼠模型来表征NF 1骨假关节病的分子缺陷，随后用作临床前模型来测试各种药理学试剂对骨愈合的矫正作用。

DESCRIPTION (provided by applicant): 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. PUBLIC HEALTH RELEVANCE: The studies proposed in this application aim at characterizing the molecular defects of NF1 bone pseudoarthrosis by the generation of new mouse models, subsequently used as pre-clinical models to test the corrective effect of various pharmacological agents on bone healing.