Mitochondrial genetics as a determinant of bone health

摘要 线粒体在骨组织生理学和病理学中的作用尚不清楚。我们的长期目标 是填补这一知识空白，而这项高风险的提议是朝着这一目标迈出的一步。它将测试线粒体是否 遗传学(mtDNA单倍型)影响成骨细胞(OB)及其前体的骨表型和功能， 骨髓基质(又名骨髓间充质干细胞。这里的科学前提是：1) 线粒体氧化磷酸化是成骨分化所必需的；2)线粒体 功能障碍在骨老化中起重要作用；3)线粒体疾病患者骨骼脆弱；4) 为适应寒冷气候而形成的mtDNA单倍群效率较低的欧亚人也有较弱的 骨骼与线粒体DNA单倍群更有效的非洲人相比L；和5)C3H/母鸡 MtDNA单倍型效率更高的(C3H)小鼠的骨骼也比C57BL/6J(C57)小鼠的骨骼更强壮 高效线粒体DNA单倍型。为了研究核vsmtdna基因组对表型的贡献，我们将使用 微妙的新遗传模型，线粒体/核交换(MNX)小鼠。这些MNX小鼠有C57或C3H C3Hmt和C3Hn分别为C57n和C57mt。这些小鼠体内的细胞 根据线粒体DNA单倍型而不是核背景来显示OxPhos的活性。我们的试点数据 结果表明，C57n；C3Hmt BMSCs的成骨能力较高，而C3Hn；C57mt BMSCs的成骨能力较低 相应的对照分别为C57和C3H。我们还观察到3个月龄的F小鼠的骨量 反映其线粒体DNA单倍群(C57n；C3Hmt&Gt；C57；C3Hn；C57mt&lt；C3h)。我们的核心假设是 线粒体遗传学是骨髓间充质干细胞成骨潜能、成骨功能和成骨能力的重要决定因素 骨表型。为了测试它，我们将确定MNX小鼠是否改变了骨表型(目标1)和改变 骨髓间充质干细胞成骨和成骨功能及线粒体-核通讯(目标2) 与它们的野生型对照相比。如果成功，这个项目将为我们的新方向奠定坚实的基础 研究和骨领域的一般情况下，线粒体遗传学的骨。

Abstract The role of mitochondria in bone tissue physiology and pathology remains understudied. Our long-term goal is to fill this gap of knowledge and this high risk proposal is a step towards this goal. It will test if mitochondrial genetics (mtDNA haplotype) influences bone phenotype and function of osteoblasts (OB) and their precursors, bone marrow stromal (a.k.a. mesenchymal stem) cells (BMSCs). The scientific premise here is that: 1) mitochondrial oxidative phosphorylation (OxPhos) is required for osteogenic differentiation; 2) mitochondrial dysfunction plays a significant role in bone aging; 3) patients with mitochondrial diseases have fragile bones; 4) Eurasians with ‘less efficient’ mtDNA haplogroups developed as an adaptation to cold climate, also have weaker bones when compared to people of African descent with ‘more efficient’ mtDNA haplogroup L; and 5) C3H/HeN (C3H) mice with more efficient mtDNA haplotype, also have stronger bones then C57BL/6J (C57) mice with less efficient mtDNA haplotype. To study contributions of nuclear vs mtDNA genome to a phenotype, we will use a delicate new genetic model, mitochondrial/nuclear exchange (MNX) mice. These MNX mice have C57 or C3H nuclear background but C3H and C57 mtDNA, respectively (C57n;C3Hmt and C3Hn;C57mt). Cells in these mice show OxPhos activity according to their mtDNA haplotype rather than their nuclear background. Our pilot data show that C57n;C3Hmt BMSCs have higher, while C3Hn;C57mt BMSCs have lower osteogenic potential than their corresponding controls, C57 and C3H, respectively. We also observed that bone accrual in 3 mo old F mice reflected their mtDNA haplogroup (C57n;C3Hmt > C57 while C3Hn;C57mt < C3H). Our central hypothesis that mitochondrial genetics is a strong determinant of BMSC osteogenic potential, OB bone-forming function, and bone phenotype. To test it, we will determine if MNX mice have altered bone phenotype (Aim 1) and altered BMSC osteogenic and OB bone-forming function and mitochondrio-nuclear communication (Aim 2) when compared to their wild type controls. If successful, this project will lay strong foundation for a new direction in our research and bone field in general, mitochondrial genetics of bone.