Understanding Muscle Regeneration Impairment in Aging Veterans

描述(由申请人提供)： 衰老、萎缩的骨骼肌在受到与年轻时相同的压力时表现出明显的再生能力受损。对于正在向虚弱过渡或试图从关节手术中恢复的退伍军人来说，这是一个重大的担忧，因为萎缩加剧，这些患者尽管付出了密集的体力努力，但无法将肌肉质量恢复到手术前的水平。这个项目的首要目标是促进对导致肌肉再生损伤的分子机制的了解。人们普遍认为，指导发育性肌肉发生的一系列复杂的协调活动--主要是肌肉前体(卫星细胞，SC)招募和净肌肉蛋白质合成--在出生后肌肉再生过程中被概括。确定在衰老肌肉中破坏这些过程的关键机制对于改善老年人的再生反应至关重要。通过人类肌肉基因组微阵列和网络图谱，以及蛋白质水平的后续研究，我们已经确定了年龄特定的转录组对机械应激的反应-候选信号通路和生物过程在老年(77岁)比年轻(34岁)的肌肉中发生了独特的改变(在转录水平上)-这推动了我们新颖的中心假设，即由于静息肌肉对炎症介质的敏感度增加，从而扰乱了成功再生所必需的肌肉生成过程，从而削弱了老年肌肉的再生。利用我们从四个年龄组(25岁、35岁、61岁和72岁)的158名成年人(90名女性，68名男性)在标准化机械应力前后收集的组织信息库，这一假设将通过以下一系列目标进行验证，这些目标集中在人类肌肉组织标本和原代干细胞中的分子和蛋白质水平的细胞信号研究，以及人类基因组微阵列。具体目的1.我们将确定年龄和性别对静息和机械应激诱导的影响：细胞因子信号转导[NFkB、SAPK/JNK(TNF-1、IL-1)、JAK/STAT3(IL-6)]；热休克蛋白含量；泛素蛋白酶体活性；翻译起始信号；以及骨骼肌促肌原转录因子的表达。具体目的2.确定供者年龄对原代培养的人干细胞对炎性细胞因子敏感性的影响。具体目标3：虽然我们的微阵列揭示并足以定向靶向1-2，但它们是初步的(8名老年人，8名年轻人)。因此，我们将进行额外的基因组阵列，以绘制性别特定的、与年龄相关的转录组对机械应激反应的开始和进展；确定其他可能被证明是年龄x性别差异的重要中介的其他新靶点。我们完全期待这一系列新颖的目标能够揭示损伤的原因以及促进老年人肌肉再生的目标。 公共卫生相关性： 随着退伍军人年龄的增长，他们骨骼肌的两个重要变化会对他们的身体功能和生活质量产生负面影响：1)肌肉变小(萎缩)；2)肌肉受伤后自我修复的能力降低(再生能力受损)。这些都是试图从受伤或关节手术中恢复的老年退伍军人的主要担忧，因为这些患者尽管付出了密集的体力努力，但无法将肌肉质量恢复到手术前的水平。这项研究项目的主要目标是确定随着个人年龄的增长而导致肌肉再生障碍的关键因素。因此，该项目具有极高的科学前景，并与年迈的退伍军人高度相关。

DESCRIPTION (provided by applicant): Aging, atrophied skeletal muscles demonstrate a markedly impaired regenerative capacity when exposed to the same stress as young. This is a significant concern for veterans transitioning toward frailty or attempting to recover from joint surgery, as atrophy is exacerbated and these patients are unable to restore muscle mass to pre-surgery levels despite intensive physical efforts. The overarching goal of this project is to advance knowledge of the molecular mechanisms causing muscle regeneration impairment with increasing age. There is general consensus that the complex array of coordinated activities guiding developmental myogenesis- principally muscle progenitor (satellite cell, SC) recruitment and net muscle protein synthesis-is recapitulated during postnatal muscle regeneration. Identifying key mechanisms that disrupt these processes in aging muscle is essential to improve regenerative responses among old. Via human muscle genomic microarrays and network mapping, along with protein-level follow-up studies, we have identified an age-specific transcriptome response to mechanical stress-candidate signaling pathways and biological processes that were altered (at the transcript level) uniquely in the muscles of old (77 y) compared to young (34 y)-which drives our novel, central hypothesis that impaired muscle regeneration in old results from heightened resting muscle sensitivity to inflammatory mediators and consequent disruption of myogenic processes requisite for successful regeneration. Taking advantage of our tissue repository collected from 158 adults (90 women, 68 men) across four age groups (25, 35, 61, and 72 y) before and after a standardized mechanical stress, this hypothesis will be tested via the following series of aims focused on molecular and protein-level cell signaling studies in human muscle tissue specimens and primary SCs, and on human genomic microarrays. Specific Aim 1. We will determine the effects of age and sex on resting and mechanical stress-induced: cytokine signaling [NFkB, SAPK/JNK (TNF-1, IL-1), JAK/STAT3 (IL-6)]; heat-shock protein content; ubiquitin- proteasome activity; translation initiation signaling; and pro-myogenic transcription factor expression in skeletal muscle. Specific Aim 2. We will determine the influence of donor age on the sensitivity of primary human SCs to inflammatory cytokines. Specific Aim 3: While our microarrays were revealing and sufficient to direct targeted Aims 1-2, they are preliminary (8 old, 8 young). We will therefore conduct additional genomic arrays to map the sex-specific, age-related onset and progression of changes in the transcriptome response to mechanical stress; identify other novel targets that may prove to be important mediators of age x sex differences. We fully expect this series of novel Aims to reveal causes of impairment as well as targets for potentiating muscle regeneration among old. PUBLIC HEALTH RELEVANCE: As veterans get older, two important changes in their skeletal muscles negatively affect their physical function and quality of life: 1) muscles get smaller (atrophy); and 2) muscles have a reduced ability to repair themselves after injury (impaired regenerative capacity). These are major concerns for aging veterans attempting to recover from injury or joint surgery, as these patients are unable to restore muscle mass to pre- surgery levels despite intensive physical efforts. The major goal of this research project is to determine key factors that cause muscle regeneration impairment as individuals get older. The project therefore holds an extremely high degree of scientific promise and is highly relevant to aging veterans.