Skeletal Muscle Loss and Dysfunction

项目4：骨骼肌丢失和功能障碍--LeBrasseur摘要 根据方案项目赠款的总体目标，项目4将检验以下中心假设 衰老细胞是骨骼肌衰老的机械性因素，是治疗骨骼肌衰老的新靶点 恢复肌肉性能、身体功能和组织弹性。我们的假设是基于我们的 最近的研究表明，作为衰老标志的细胞衰老在多重年龄的发生中所起的作用。 相关条件。我们的初步数据证实了细胞周期蛋白依赖的激酶抑制物的表达 衰老的标志物和中介物p21Cip1在衰老的小鼠和人的骨骼肌中增加 与身体机能的测量呈负相关。我们发现p21Cip1，与衰老相关 作为响应，培养成肌细胞的分泌表型(SASP)和抗凋亡蛋白显著增加 导致衰老的压力。然而，衰老的肌肉在成分上是异质性的，而衰老的 其他常驻细胞群，包括成纤维脂肪前体细胞、内皮细胞和免疫细胞，也可能 导致了它的退化。因此，迫切需要鉴定和综合表型。 衰老肌肉中的细胞群，衰老和机械性地导致其丢失和功能障碍。 为此，在目标1中，我们将使用携带转基因的小鼠来分离表达p21Cip1的基因 用细胞量化衰老标记物、SASP和抗凋亡信号通路 幼龄和老年小鼠。将对非衰老和衰老细胞群体进行高维映射 通过质量细胞术和先进的组织学方法完成。目标2，将直接比较 P21Cip表达细胞的遗传清除对肌肉p16INK4a表达细胞清除的影响 健康(例如，质量、纤维化和脂肪渗透)以及身体功能和弹性的测量 支持集成Healthspan表型核心。我们还将评估清算的相对有效性。 利用新型Cre-loxP系和药物开发的特定p21Cip1-细胞群 由药物发现和开发核心进行筛选。最后，目标3将检验这样一个假设，即基因和 衰老细胞的药理清除将增强肌肉形成药物对措施的影响 肌肉健康、身体机能和韧性。二次分析将包括对代谢的影响， 骨骼和心血管健康，分别与项目1、2和3合作。通过小说的使用 分析、转基因和药理学工具以及多学科方法，我们希望推动我们的 了解骨骼肌衰老的基本生物学原理。临床相关药物的应用 身体功能和复原力的测量和循证的感官治疗化合物将促进 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.