PDGF-regulated stem cells and bone disease

骨骼的生长和愈合能力是可能的，因为出生后的骨骼干细胞(SSCs)含有... 性生成成骨细胞。血小板衍生生长因子受体β(PDGFRβ)表达于 SSCs和成骨细胞，但其在体内的功能作用尚未确定。最近，人类与 据报道，PDGFRb的功能获得突变表现为进行性骨骼疾病 儿童期或青春期的骨质丢失或骨骼过度生长。然而，靶细胞类型和分子 PDGFRβ驱动的骨骼疾病的潜在机制尚不清楚。申请者的长期目标是 从机制上理解PDGF途径如何调节间充质细胞的可塑性。骨 形成是因为成骨细胞产生富含胶原蛋白的有机基质，称为类骨质，随后形成 矿化成骨头。细胞可塑性和胶原产生的缺陷可能是由 PDGF途径。因此，本提案的具体目标是确定PDGF调节的机制-- 控制SSCs的神经及其对骨骼疾病的贡献。这个项目背后的假设是 PDGFRβ通过其下游效应分子的平衡调节干细胞的增殖和分化 信号转导和转录激活因子(STAT)家族。AIM 1将使用针对SSC的CRE/LOX AP- 方法诱导血小板衍生生长因子受体β激活突变和组合状态缺失，并确定 STATS在体内介导骨病。突变鼠骨来源的原代SSCs将用于研究- PDGFRβ调节的STAT信号通路在体外还是以后调节干细胞的自我更新和分化 移植。作为另一种方法，PDGFRβ激活突变将针对软骨细胞。 AIM 2将描述具有PDGFRβ激活突变的新小鼠模型，该突变最常见于 Penttinen综合征和Kosaki过度生长综合征，分别为V665A和P584R。AIM 2也将不会- 了解激酶抑制剂对具有功能增强的PDGFRβ信号传递的小鼠的益处。AIM 3将研究小鼠 利用PDGFRβ的增强型和失调型突变来确定PDGFFRβ的调控过程 SSCS及其后代在出生后骨骼生长过程中。突变细胞将被绘制命运图以确定如何 在体内，不同水平的PDGFRβ活性调节细胞的增殖、分化和细胞命运。这项工作是前- 旨在确定PDGFRβ信号通路如何介导成骨以及如何过多或过少地介导成骨 信号产生骨骼疾病，这将指向新的治疗策略和更好的AP- 修复骨骼的方法。这些项目的成果将极大地促进对SSC规则的理解。 保守党的机制。有关介导疾病相关PDG的信号通路和细胞类型的信息- FRβ信号将为骨骼疾病的新治疗方法的发展提供信息。和识别 PDGFRβ在骨生长中的特殊作用将使其成为治疗的分子靶点。所有这一切 信息将改善对患病或受损骨骼的结构和功能的恢复。

The growth and healing ability of the skeleton is possible because postnatal skeletal stem cells (SSCs) contin- ually generate bone-forming osteoblasts. Platelet-derived growth factor receptor β (PDGFRβ) is expressed on SSCs and osteoblasts, but its functional roles have not been characterized in vivo. Recently, humans with gain-of-function mutations in PDGFRB have been reported to exhibit skeletal disease involving progressive bone loss or skeletal overgrowth during childhood or adolescence. However, the target cell type and molecular mechanisms underlying PDGFRβ-driven skeletal disease are unknown. The applicant’s long-term goal is to develop a mechanistic understanding of how the PDGF pathway regulates mesenchymal cell plasticity. Bone forms because osteoblasts produce collagen-rich organic matrix called osteoid, which subsequently becomes mineralized into bone. Defects in cell plasticity and collagen production may underlie bone diseases driven by the PDGF pathway. Therefore, the specific objective in this proposal is to identify PDGF-regulated mecha- nisms controlling SSCs and their contribution to skeletal disease. The hypothesis underlying this project is that PDGFRβ regulates SSC proliferation and differentiation through the balance of downstream effectors of the signal transducer and activator of transcription (STAT) family. Aim 1 will use an SSC-targeted Cre/lox ap- proach to induce PDGFRβ activating mutations and combinatorial STAT deletions, and determine whether STATs mediate bone disease in vivo. Primary SSCs derived from mutant mouse bones will be used to investi- gate whether PDGFRβ-regulated STAT signaling regulates SSC self-renewal and differentiation in vitro or after transplantation. As an alternative approach, PDGFRβ activating mutations will be targeted to chondrocytes. Aim 2 will characterize new mouse models with the PDGFRβ activating mutations most commonly found in Penttinen syndrome and Kosaki overgrowth syndrome, V665A and P584R, respectively. Aim 2 will also ex- plore the benefits of kinase inhibitors for mice with gain-of-function PDGFRβ signaling. Aim 3 will study mice with gain- and loss-of-function mutations in PDGFRβ to identify the processes by which PDGFRβ regulates SSCs and their progeny during postnatal skeleton growth. Mutant cells will be fate mapped to determine how different levels of PDGFRβ activity regulate proliferation, differentiation, and cell fate in vivo. This work is ex- pected to define how the PDGFRβ signaling pathway mediates osteogenesis and how too much or too little signaling generates diseases of the skeleton, which will point to novel therapeutic strategies and better ap- proaches for bone repair. The results of these projects will significantly advance understanding of SSC regula- tory mechanisms. Information about signaling pathways and cell types that mediate disease-associated PDG- FRβ signaling will inform the development of new therapeutic approaches for skeletal diseases. And identifying the specific role of PDGFRβ in bone growth will begin to establish it as a molecular target for therapy. All of this information will improve the restoration of structure and function to diseased or damaged bones.