Skeletal Muscle Loss and Dysfunction

项目4：骨骼肌损失和功能障碍-总结LeBrasseur 根据计划项目补助金的总体目标，项目4将测试中心假设， 衰老细胞在机制上促进骨骼肌衰老，并代表了一种新的药物靶点， 恢复肌肉性能，身体功能和生物体弹性。我们的假设是建立在 最近的工作证明了细胞衰老的作用，衰老的标志，在多个年龄的起源- 相关条件。我们的初步数据表明细胞周期蛋白依赖性激酶抑制剂的表达 p21 Cip 1是衰老的标志物和介质，在老年鼠和人骨骼肌中增加， 与身体功能的测量呈负相关。我们发现，p21 Cip 1，衰老相关的， 分泌表型（SASP）和抗凋亡蛋白在培养的成肌细胞中显着增加， 导致衰老的压力然而，衰老的肌肉在组成上是异质的， 其它驻留细胞群，包括成纤维脂肪祖细胞、内皮细胞和免疫细胞，也可 有助于其退化。因此，迫切需要鉴定和全面分析表型， 老化肌肉中的细胞群衰老并机械地导致其损失和功能障碍。 为此，在目标1中，我们将使用携带转基因的小鼠，该转基因能够分离表达p21 Cip 1的小鼠。 细胞，以量化衰老的标志物，SASP，和抗凋亡途径的肌肉驻留细胞， 年轻和年老的老鼠非衰老和衰老细胞群的高维映射将是 通过大量细胞计数和先进的组织学方法完成。目标2，将直接比较 p21 Cip表达细胞的遗传清除对肌肉上p16 Ink 4a表达细胞的清除的影响 健康（例如，质量，纤维化和脂肪浸润）以及身体功能和弹性的测量， 支持Integrated Healthspan Phenotyping Core我们还将评估清算的相对功效 使用新的Cre-LoxP系和开发的药理学试剂特异性p21 Cip 1细胞群， 通过药物发现和开发核心筛选。最后，目标3将检验遗传和 衰老细胞的药理学清除将增强肌肉生成药物对测量的效果 肌肉健康、身体功能和恢复力的重要性。次要分析将包括对代谢的影响， 骨和心血管健康分别与项目1、2和3合作。通过使用小说 分析，转基因和药理学工具和多学科的方法，我们希望推进我们的 了解骨骼肌老化的基本生物学。临床相关的应用 身体功能和恢复力的措施以及基于证据的sennis化合物将有助于 将临床前发现转化为临床应用。

PROJECT 4: Skeletal Muscle Loss and Dysfunction – SUMMARY LeBrasseur In line with the overall goal of the Program Project Grant, Project 4 will test the central hypothesis that senescent cells mechanistically contribute to skeletal muscle aging and represent a novel druggable target to restore muscle performance, physical function, and organismal resilience. Our hypothesis is founded on our recent work demonstrating the role of cellular senescence, a hallmark of aging, in the genesis of multiple age- related conditions. Our preliminary data demonstrate expression of the cyclin-dependent kinase inhibitor p21Cip1, a marker and mediator of senescence, increases in aged murine and human skeletal muscle and negatively associates with measures of physical function. We show that p21Cip1, senescence-associated secretory phenotype (SASP), and anti-apoptotic proteins markedly increase in cultured myoblasts in response to senescence-inducing stress. Aged muscle is compositionally heterogenous, however, and senescence of other resident cell populations, including fibroadipogenic progenitor, endothelial, and immune cells, may also contribute to its degeneration. Consequently, there is a critical need to identify and comprehensively phenotype the cell populations within aged muscle that senesce and mechanistically contribute to its loss and dysfunction. To this end, in Aim 1 we will use mice harboring a transgene that enables the isolation of p21Cip1-expressing cells to quantify markers of senescence, the SASP, and anti-apoptosis pathways in muscle-resident cells of young and aged mice. High dimensional mapping of non-senescent and senescent cell populations will be accomplished through mass cytometry and advanced histological approaches. Aim 2, will directly compare the effects of genetic clearance of p21Cip-expressing cells to clearance of p16Ink4a-expressing cells on muscle health (e.g., mass, fibrosis, and fat infiltration) and measures of physical function and resilience with the support of Integrated Healthspan Phenotyping Core. We will also assess the relative efficacy of clearing specific p21Cip1-cell populations using novel Cre-LoxP lines and pharmacological agents developed and screened by the Drug Discovery and Development Core. Finally, Aim 3 will test the hypothesis that genetic and pharmacological clearance of senescent cells will potentiate the effects of a muscle building drug on measures of muscle health, physical function, and resilience. Secondary analyses will include the effects on metabolic, bone, and cardiovascular health in partnership with Projects 1, 2, and 3, respectively. Through the use of novel analytical, transgenic, and pharmacological tools and a multidisciplinary approach, we expect to advance our understanding of the fundamental biology of skeletal muscle aging. The application of clinically-relevant measures of physical function and resilience and evidence-based senotherapeutic compounds will facilitate the translation of preclinical discoveries to clinical application.