Restoring the regenerative capacity of the aged muscle

摘要 肌肉质量的减少，肌肉减少症，是老年人面临的一个主要医学问题， 代谢功能丧失、残疾、发病率和死亡率。此外，需要延长培养时间 以获得再生医学所需的大量细胞。因此，细胞的质量， 用于细胞治疗的组织工程可能会受到复制性衰老的影响。 在过去的几年里，我们的实验室发现，多能性相关的胚胎表达， 转录因子NANOG可以逆转衰老，完全恢复细胞的分化潜能。 衰老间充质干细胞（MSC）和来自早老症（加速老化疾病）患者的细胞转化为 功能性平滑肌细胞我们还发现，NANOG可以逆转衰老的能力受损， 干细胞产生III型胶原蛋白和弹性蛋白，这是严重影响老化和影响机械 皮肤、动脉和骨骼肌等组织的特性。最近，我们发现NANOG 逆转了细胞衰老的标志，恢复了衰老骨骼的代谢程序， 成肌细胞，最终恢复其形成收缩肌管的能力，并响应于 损伤 在这项提案中，我们试图更好地了解介导NANOG体外作用的机制， 通过以下目的在体内。在目标1中，我们将研究NANOG对成肌细胞衰老的影响， 传统培养以及使用生物工程3D骨骼肌组织。NANOG在细胞后表达 达到衰老，从而使我们能够测量逆转的老化表型使用过多的 细胞、分子和功能测定。在目标2中，我们将研究NANOG对恢复代谢的影响。 老年成肌细胞的功能。我们建议详细研究NANOG诱导的代谢重编程， 老化的细胞，并研究可能介导这些影响的潜在信号通路。最后，在目标3中， 开发一种非常创新的小鼠模型，以研究NANOG对动物生理学、骨骼 肌肉新陈代谢和再生 影响：这是一个非常创新的建议，旨在研究胚胎的潜力。 转录因子，以改善衰老的影响，增强老年骨骼肌的再生能力 （SkM）。了解介导NANOG对代谢重编程的影响的机制， 老化的SkM可能有助于识别新的药物靶点，并设计创新的策略来恢复 老化组织的功能。鉴于美国和世界人口老龄化的激增， 衰老对骨骼肌的影响以及由此产生的影响老年人的脆弱状况， 这项工作可能对再生医学和老年患者的生活质量产生重大影响。

ABSTRACT Age-related loss in muscle mass, sarcopenia, is a major medical problem facing the elderly and correlates with loss of metabolic function, disabilities, morbidity, and mortality. In addition, prolonged culture times are required to obtain the large numbers of cells necessary for regenerative medicine. As a result, the quality of the cells that are used to engineer tissues for cell therapies may be compromised by replicative senescence. In the past few years, our laboratory discovered that expression of a pluripotency-associated embryonic transcription factor, NANOG, could reverse senescence and completely restore the differentiation potential of senescent mesenchymal stem cells (MSC) and cells from progeria (accelerated aging disease) patients into functional smooth muscle cells. We also discovered that NANOG could reverse the impaired ability of senescent stem cells to produce collagen type III and elastin, which are severely affected by aging and affect the mechanical properties of tissues such as skin, arteries and skeletal muscle. Most recently we discovered that NANOG reversed the hallmarks of cellular senescence and restored the metabolic program of senescent skeletal myoblasts, ultimately restoring their ability form contractile myotubes and regenerate in response to injury. In this proposal we seek to better understand the mechanisms that mediate the effect of NANOG in vitro and in vivo through the following aims. In Aim 1, we will examine the effects of NANOG on myoblast senescence in traditional cultures as well as using bioengineered 3D skeletal muscle tissues. NANOG is expressed after cells reach senescence, thereby enabling us to measure the reversal of the aging phenotype using a plethora of cellular, molecular and functional assays. In Aim 2, we will study the effects of NANOG on restoring the metabolic function of aged myoblasts. We propose to study in detail the NANOG-induced metabolic reprogramming of aged cells and investigate potential signaling pathways that may mediate these effects. Finally, in Aim 3 we will develop a very innovative mouse model to investigate the effects of NANOG on animal physiology, skeletal muscle metabolism and regeneration. Impact: This is a very innovative proposal that seeks to investigate the potential of an embryonic transcription factor to ameliorate the effects of aging and enhance the regenerative ability of aged skeletal muscle (SkM). Understanding the mechanism(s) that mediate the effects of NANOG on metabolic reprogramming of aged SkM may enable identification of novel druggable targets and design of innovative strategies to restore the function of aged tissues. Given the surge in the aging population in the US and the world, the debilitating effects of aging on skeletal muscle and the resulting frailty condition affecting the elderly, successful attainment of this work may have significant impact in regenerative medicine and the quality of life of elderly patients.