The role of cellular senescence in skeletal muscle loss and dysfunction

项目总结/摘要 本提案的目标是（1）获得必要的实验技能和职业培训， 制定转化研究计划，调查骨骼肌萎缩的潜在机制;（2） 产生确定靶向衰老细胞以恢复肌肉大小的可行性所必需的数据， 功能肌肉减少症是一种与年龄相关的骨骼肌消耗综合征， 生活质量和高保健利用率。肌肉减少症的病因尚未完全了解， 目前没有有效的治疗方法。识别介导肌肉减少症的过程对于开发 药物治疗衰老细胞随着年龄的增长和疾病的解剖部位积累。因此，在本发明中， 它们被认为是合理的治疗靶点。事实上，在小鼠中， 改善多种组织的功能和健康参数。我们的初步数据显示（1）衰老后- 有丝分裂肌纤维在肌肉减少症小鼠中积累，（2）细胞周期蛋白依赖性激酶抑制剂p21是一个关键的 调节肌纤维衰老，和（3）一个子集的肌细胞核内的多核肌纤维， 特别容易衰老诱导。我将使用小鼠模型，允许肌肉纤维特异性 p21的标记和调节，以促进我们对肌纤维衰老的理解，并检查 衰老对肌肉功能障碍的直接贡献。在目标1中，我将在肌肉纤维中过表达p21， 并应用经过充分验证的衰老标志物以及全转录组分析来确定 肌纤维衰老的核心特性，并确定可作为治疗的调节过程 目标的在目标2中，我将使用功能获得和功能丧失的p21模型，并评估肌肉的测量 健康、功能和大小，以确定骨骼肌中衰老细胞负荷的临床相关性。在 目的3、将真菌鉴定和分离技术结合起来进行多组学分析， 衰老和非衰老的肌细胞核亚群之间的差异，以获得对这些因素的新认识 调节肌肉衰老。K99阶段将在马约诊所进行，重点是 获得完成拟议目标所需方法方面的指导培训。R 00阶段将是 在我的独立实验室进行，并将专注于分析小鼠组织和数据，发表研究结果， 基于这些结果开发R 01应用程序。这项建议协同新的技能，在先进的 衰老细胞鉴定、成像、生物信息学和药物靶点发现技术， 与我导师的关注点截然不同的轨迹。这项工作将为一个独立的 研究事业阐明骨骼肌功能障碍的细胞机制，目的是翻译 将这些发现转化为改善人类健康和福祉的疗法。

PROJECT SUMMARY/ABSTRACT The objectives of this proposal are to (1) obtain the experimental skills and career training necessary to develop a translational research program investigating mechanisms underlying skeletal muscle wasting and (2) generate the data necessary to determine the feasibility of targeting senescent cells to restore muscle size and function. Sarcopenia is a debilitating age-related skeletal muscle wasting syndrome associated with poor quality of life and high health care utilization. The etiology of sarcopenia is not fully understood, and there are currently no effective treatments. Identifying the processes mediating sarcopenia is critical for developing pharmacologic therapies. Senescent cells accumulate with age and at the anatomical sites of disease. Thus, they are regarded as a logical therapeutic target. Indeed, in mice, the targeted elimination of senescent cells improves function and parameters of health in multiple tissues. Our preliminary data show (1) senescent post- mitotic muscle fibers accumulate in sarcopenic mice, (2) the cyclin-dependent kinase inhibitor p21 is a critical regulator of muscle fiber senescence, and (3) a subset of myonuclei within multi-nucleated muscle fibers are uniquely vulnerable to senescence induction. I will use mouse models that allow for muscle fiber-specific labeling and modulation of p21 to advance our understanding for muscle fiber senescence and examine the direct contribution of senescence to muscle dysfunction. In Aim 1, I will overexpress p21 in muscle fibers in vivo and apply well-validated markers of senescence together with transcriptome-wide analyses to determine the core properties of muscle fiber senescence and identify regulatory processes that may serve as therapeutic targets. In Aim 2, I will use gain-of-function and loss-of-function p21 models and assess measures of muscle health, function, and size to determine the clinical relevance of senescent cell burden in skeletal muscle. In Aim 3, I will use myonuclear identification and isolation techniques together multiomic profiling to examine differences between senescent and non-senescent subsets of myonuclei to gain new insight into the factors regulating myonuclear senescence. The K99 phase will be conducted at Mayo Clinic and will focus on obtaining mentored training in methods required to complete the proposed aims. The R00 phase will be conducted in my independent lab and will focus on analyzing mouse tissues and data, publishing findings, and developing an R01 application based on these results. This proposal synergizes new skills in advanced senescent cell identification, imaging, bioinformatics, and drug target discovery techniques to create a research trajectory that is distinct from my mentors’ foci. This work will produce a robust foundation for an independent research career elucidating cellular mechanisms of skeletal muscle dysfunction with the aim of translating these findings into therapies to improve human health and well-being.