Role of Extracellular Vesicles in Bone-Muscle Crosstalk with Aging

摘要 骨质疏松症和肌肉减少症是经常一起发生并降低生活质量的衰老疾病 在老年人口中。有证据表明，骨骼和肌肉之间的信号串扰是通过 循环和局部介质，导致肌肉骨骼串扰可能协调年龄的概念- 相关的退行性变化。细胞间通讯的一个令人兴奋的新范例是细胞外 囊泡（EV）（外来体和微泡）可能提供了一种新的机制， 细胞还提出循环肌肉来源的外泌体（称为“exersomes”）可 调节运动对身体的一些有益作用。EV是脱落的膜结合颗粒 从携带蛋白质、mRNA和microRNA（miRNAs）的细胞中提取。电动车与目标电池对接， 运送货物并改变其功能我们已经证明年轻和年老的骨细胞会脱落EV， 这可能为成骨细胞功能的调节提供新的机制。活细胞成像显示 骨细胞将EV从它们的细胞体和树突中排出，并可能将它们排出到循环中。骨细胞 EV被成骨细胞和成肌细胞摄取，并对成骨细胞具有有效的作用，以促进 向早期骨细胞表型分化。来自成肌细胞和肌管的EV被 并诱导β-连环蛋白信号传导。这些发现导致我们的总体假设，细胞外 囊泡（EV）是骨和肌肉细胞功能的重要调节因子， 肌肉和骨骼之间的相互作用机制可能调节与年龄相关的骨质疏松症 和肌肉减少症。将使用体外和体内方法对这一假设进行测试， 在年轻和老年小鼠模型中使用荧光报告分子进行活体成像以标记骨骼和肌肉 细胞目的1探讨EV在体外调控骨细胞-成骨细胞相互作用中的作用 以及衰老和锻炼如何改变这一点。这将使用来自成骨细胞的EV完成， 骨细胞系和原代细胞，以确定EV对骨细胞分化功能的影响。 细胞类型。目的2将确定EV在调节肌肉-骨骼串扰中的作用，以及它如何被改变。 老化和锻炼。这将使用来自成肌细胞、成骨细胞和骨细胞系的EV来完成， 原代细胞，以确定EV对相互细胞类型的分化功能的影响。在这两个目标中， 活细胞和活体成像将确定肌肉和骨细胞中EV释放和摄取的动力学 在体外和体内。将使用年轻和老年小鼠模型，进行和不进行轮跑运动 在体外和体内测定老化和运动对EV释放、组成和功能的影响。 这些研究可能会导致范式转变的洞察机制之间的分子串扰 骨骼和肌肉，并将为开发肌肉和骨骼衍生电动汽车的潜力铺平道路， 循环生物标志物和作为年龄相关的骨和肌肉损失的新疗法。

ABSTRACT Osteoporosis and sarcopenia are diseases of aging that frequently occur together and reduce quality of life in the elderly population. Evidence is emerging for signaling crosstalk between bone and muscle via circulating and local mediators, leading to the concept that muscle-bone crosstalk may coordinate age- related degenerative changes. An exciting new paradigm in cell-cell communication is that extracellular vesicles (EV) (exosomes and microvesicles) may provide a novel mechanism for communication between cells. It has also been proposed that circulating muscle-derived exosomes (termed “exersomes”) may mediate some of the beneficial effects of exercise in the body. EV are membrane-bound particles shed from cells with a cargo of proteins, mRNAs and microRNAs (miRNAs). The EV dock with a target cell, delivering their cargo and altering its function. We have shown that young and aged osteocytes shed EV, which may provide a novel mechanism for regulation of osteoblast function. Live cell imaging suggests osteocytes shed EV from their cell body and dendrites and may shed them into the circulation. Osteocyte EV are taken up by osteoblasts and myoblasts and have potent effects on osteoblasts to promote differentiation towards an early osteocyte phenotype. EV from myoblasts and myotubes are taken up by osteocytes and induce β-catenin signaling. These findings lead to our overall hypothesis that extracellular vesicles (EV) are important regulators of bone and muscle cell function and provide a novel mechanism for crosstalk between muscle and bone that may regulate age-related osteoporosis and sarcopenia. This hypothesis will be tested using complimentary in vitro and in vivo approaches and using intravital imaging in young and aged mouse models with fluorescent reporters to tag bone and muscle cells. Aim 1 will determine the role of EV in regulating osteocyte-osteoblast reciprocal interactions in vitro and in vivo and how this is altered by aging and exercise. This will be done using EV from osteoblast and osteocyte cell lines and primary cells to determine EV effects on the differentiated function of the reciprocal cell type. Aim 2 will determine the role of EV in regulating muscle-bone crosstalk and how it is altered by aging and exercise. This will be done using EV from myoblast, osteoblast and osteocyte cell lines and primary cells to determine EV effects on the differentiated function of the reciprocal cell types. In both aims, live cell and intravital imaging will determine the kinetics of EV release and uptake in muscle and bone cells in vitro and in vivo. Young and aged mouse models will be used with and without wheel running exercise to determine in vitro and in vivo the effect of aging and exercise on EV release, composition and function. These studies may result in paradigm shifting insight into the mechanisms of molecular crosstalk between bone and muscle and will pave the way for exploiting the potential of muscle and bone derived EVs as circulating biomarkers and as novel therapeutics for age related bone and muscle loss.