Understanding Muscle Regeneration Impairment in Aging Veterans

描述（由申请人提供）： 当暴露在与年轻时相同的压力下时，老化、萎缩的骨骼肌表现出明显受损的再生能力。这是一个重要的问题，退伍军人过渡到脆弱或试图从关节手术中恢复，因为萎缩加剧，这些患者无法恢复肌肉质量到术前水平，尽管密集的身体努力。该项目的总体目标是推进对随着年龄增长导致肌肉再生障碍的分子机制的认识。有一个普遍的共识，指导发育的肌肉发生的协调活动的复杂阵列-主要是肌肉祖细胞（卫星细胞，SC）招聘和净肌肉蛋白质合成-在出生后的肌肉再生重演。确定破坏衰老肌肉中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，沿着蛋白质水平的后续研究，我们已经确定了一个年龄特异性转录组对机械应力的反应-候选信号通路和生物过程被改变（在转录水平上）与年轻人（34岁）相比，老年人（77岁）的肌肉是独一无二的-这推动了我们的小说，一个中心假设是，老年人肌肉再生受损是由于静息肌肉对炎症介质的敏感性提高，从而破坏了成功再生所必需的肌源性过程。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）中收集的组织库，在标准化机械应力之前和之后，将通过以下一系列目标来测试这一假设，这些目标集中在人类肌肉组织标本和原代SC的分子和蛋白质水平的细胞信号传导研究以及人类基因组微阵列上。具体目标1。我们将确定年龄和性别对静息和机械应力诱导的影响：细胞因子信号传导[NFkB，SAPK/JNK（TNF-1，IL-1），JAK/STAT 3（IL-6）];热休克蛋白含量;泛素-蛋白酶体活性;翻译起始信号传导;骨骼肌中促肌生成转录因子表达。具体目标2。我们将确定供体年龄对原代人干细胞对炎性细胞因子敏感性的影响。具体目标3：虽然我们的微阵列显示并足以指导目标1-2，但它们是初步的（8个老年人，8个年轻人）。因此，我们将进行额外的基因组阵列，以绘制性别特异性，年龄相关的发病和机械应力的转录组响应的变化的进展;确定其他新的目标，可能被证明是年龄x性别差异的重要介质。我们完全期待这一系列新的目标，以揭示损伤的原因，以及加强老年人肌肉再生的目标。

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.