Mitochondria and TFAM in Osteoblast Biology

成骨细胞生物学中的线粒体和 TFAM

• 批准号: 9977917
• 负责人: Ernestina Schipani
• 金额: $ 23.02万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-15 至 2020-10-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9977917
• 关键词: Adult; Affect; Aging; Bioenergetics; Biological; Biology; Bone Marrow; Calvaria; Cell Differentiation process; Cells; Cellular Metabolic Process; Complement; Consumption; Cre driver; Data; Development; Disease; Electron Transport; Energy Metabolism; Ensure; Genes; Genetic Transcription; Glycolysis; Homeostasis; Hypoxia Inducible Factor; Impairment; In Vitro; Knowledge; Lead; Learning; Maintenance; Measures; Membrane Potentials; Mesenchymal; Mesenchymal Differentiation; Metabolic; Metabolic Bone Diseases; Metabolism; Mitochondria; Mitochondrial DNA; Mus; Mutant Strains Mice; Mutation; Newborn Infant; Osteoblasts; Osteocalcin; Oxidative Phosphorylation; Oxygen; Pathological fracture; Periosteal Cell; Phenotype; Play; Process; Production; Regulation; Role; Secondary to; Source; Stromal Cells; Testing; Time; Up-Regulation; aged; bone; bone mass; cell type; experimental study; factor A; gain of function mutation; in vitro Assay; in vivo; loss of function mutation; mtTF1 transcription factor; mutant; novel; novel therapeutics; osteoblast differentiation; osteogenic; osteoprogenitor cell; overexpression; postnatal; prevent; progenitor; transcription factor

ABSTRACT Once thought to be a mere consequence of the state of the cell, metabolism is now known to play a critical role in dictating cell differentiation. Non-oxidative glycolysis and oxidative phosphorylation (OxPhos) are the two sources of intracellular ATP. Factors that increase osteoblast activity and bone mass such as the Hypoxia- Inducible Factor 1a (HIF1) have been shown to activate non-oxidative glycolysis. In vitro osteogenic differentiation of mesenchymal progenitors increases both non-oxidative glycolysis and OxPhos. However, the role of OxPhos in osteoblast biology in vivo is largely unexplored. To fill this gap in knowledge, we generated a mutant mouse lacking Mitochondrial Transcription Factor A (TFAM) in uncommitted mesenchymal progenitors and their descendants (PRX;TFAMf/f). TFAM regulates transcription of the mitochondrial genes that encode thirteen subunits of the electron transport chain and thus controls OxPhos. Analysis of 3-week-old PRX;TFAMf/f bones revealed the presence of a severe low bone mass phenotype with spontaneous fractures in mutants. Our data thus indicate that mesenchymal TFAM is necessary for bone mass accrual. In addition, we provided preliminary evidence that loss of TFAM inhibits the in vitro differentiation of bone marrow stromal cells (BMSCs) into osteoblasts and significantly reduces their intracellular levels of ATP. Impairment of OxPhos is the most powerful, consistent and best characterized biological consequence of loss of TFAM across numerous cell types." " However, TFAM also regulates duplication of mitochondrial DNA, and mitochondria have functions that go beyond OxPhos and ATP production. Therefore, to establish if the impairment of OxPhos and thus the decreased intracellular ATP is the primary cause of the PRX;TFAMf/f bone phenotype, we asked whether correcting the ATP levels through forced upregulation of non-oxidative glycolysis would prevent the low bone mass of PRX;TFAMf/f mice. For this purpose, we crossed PRX;TFAMf/f mutants with mice overexpressing a constitutively stabilized HIF1 in the same cells (PRX;HIF1dPAf/f). HIF1 is known to promote non-oxidative glycolysis and to impair OxPhos.. Preliminary analysis of PRX;TFAMf/f;HIF1dPAf/f double mutant mice revealed that increased HIF1 activity corrected the bone phenotype of PRX;TFAMf/f mutants. Building on these findings, we will now test the hypothesis that TFAM in cells of the osteoblast lineage is crucial for bone mass accrual and maintenance by promoting OxPhos and thus ensuring the proper levels of intracellular ATP. We will test our hypothesis in three Aims. Progressive impairment of mitochondrial activity has been associated with numerous aging-related diseases, but it is uncertain whether this association is due, at least in part, to a dysfunctional OxPhos. The successful accomplishment of the experiments we propose in this application will expand and deepen our knowledge of the role of energy metabolism, particularly OxPhos, in the regulation of osteoblast differentiation and bone mass accrual and maintenance. "

抽象的 曾经被认为仅仅是细胞状态的结果，现在已知新陈代谢起着关键作用 在决定细胞分化时。非氧化糖酵解和氧化磷酸化（OXPHOS）是两个 细胞内ATP的来源。增加成骨细胞活性和骨骼质量（例如缺氧）的因素 诱导因子1a（HIF1）已显示可激活非氧化糖酵解。体外成骨 间充质祖细胞的分化增加了非氧化糖酵解和Oxphos。但是， Oxphos在体内成骨细胞生物学中的作用在很大程度上没有探索。为了填补这一知识的空白，我们产生了一个 缺乏线粒体转录因子A（TFAM）的突变小鼠在无核心祖细胞中 和他们的后代（PRX; TFAMF/F）。 TFAM调节编码线粒体基因的转录 电子传输链的13个亚基，从而控制Oxphos。分析3周大的PRX; TFAMF/F 骨头揭示出存在突变体中自发性骨折的严重低骨质量表型。 因此，我们的数据表明，间充质TFAM对于骨质量应计是必需的。此外，我们提供了 初步证据表明，TFAM损失抑制了骨髓细胞的体外分化 （BMSC）成骨细胞，并显着降低其细胞内ATP水平。 Oxphos的损害是 最强大，最一致和最佳特征的生物学后果是跨越TFAM 但是，TFAM还调节线粒体DNA的重复，线粒体的重复 超越OXPHOS和ATP产生的功能。因此，确定oxphos和 因此，细胞内ATP降低是PRX; TFAMF/F骨表型的主要原因，我们问 是否通过强迫上调非氧化糖酵解来纠正ATP水平是否会阻止 PRX的低骨头； TFAMF/F小鼠。为此，我们用小鼠越过PRX; TFAMF/F突变体 在同一细胞（PRX; HIF1DPAF/F）中过表达组成型HIF1。已知HIF1促进 非氧化糖酵解和损害Oxphos。 小鼠表明，增加的HIF1活性纠正了PRX的骨表型； TFAMF/F突变体。建立 这些发现，我们现在将检验以下假设：成骨细胞谱系中的TFAM对于骨骼至关重要 通过促进OXPHOS，从而确保细胞内ATP的适当水平，从而获得质量应计和维持。 我们将以三个目标来检验我们的假设。线粒体活性的进行性损害已经 与许多与衰老有关的疾病有关，但尚不确定该关联是否到期，至少在 部分，发生功能失调的OXPHOS。我们提出的实验的成功完成 应用将扩展并加深我们对能源代谢，尤其是Oxphos的作用的了解， 调节成骨细胞分化以及骨骼质量应计和维持。 “