Satellite stem cell biology

描述（由申请人提供）：患有肌肉减少症的人数大量增加，以及由此产生的残疾、痛苦和辅助护理生活费用的负担正在发生。在老年人和老年动物的肥大模型中已经报道了骨骼肌生长失败。后肢制动导致骨骼肌萎缩后，老年大鼠的骨骼肌在77天内不会再生，而年轻大鼠的骨骼肌在30天内就惊人地完全再生。这些事实表明迫切需要了解老年人肌肉萎缩和虚弱的细胞机制。该提案的长期目标是更好地了解在衰老和缺乏体力活动期间损害肌肉祖细胞增殖和分化的因素，这些因素加速了衰老期间的肌肉萎缩。由于IGF-I挽救了老年大鼠的肌肉减少症和肌肉从固定中再生的失败，具体目标1将这些观察扩展到细胞机制。特异性目的1的一般假设是IGF-I通过衰老Fischer 344 x Brown Norway大鼠的原代大鼠肌肉祖细胞中的核FoxO 1水平调节p27 Kip 1、Gadd 45和MnSOD基因的表达。医学的一个范例是识别负责病理的分子，以改善预防和治疗，这是具体目标1的目标之一。具体目标2将确定p53和Sir 2在损害从老年动物的骨骼肌或从年轻和老年动物的固定肢体中获取的肌肉祖细胞的增殖和肌原性潜能中发挥的作用。p53和Sir 2的过表达和沉默将分别用于产生功能的获得和丧失。具体目标3将采用转录谱分析来鉴定先前未鉴定的卫星细胞、卫星细胞侧群和年轻、成年、I和老年分化肌管中的mRNA差异，以提供新的候选因子，其可以被测试为有助于细胞行为随衰老的差异。从鉴定的mRNA中，选择基因用于克隆和功能分析，以确定它们的过表达或沉默是否以与衰老表型一致的方式改变肌细胞表型。研究结果将为制定预防和治疗肌肉减少症和身体虚弱的疗法提供更科学的依据。

DESCRIPTION (provided by applicant): A massive increase in the number of humans with sarcopenia, and the resulting burden of their disability, suffering, and the expense of assisted care living is occurring. Skeletal muscle growth failures have been reported in aged humans and hypertrophy models of aged animals. Following atrophy by hindlimb immobilization, skeletal muscle in aged rats does not regrow for 77 days, whereas in young rats regrowth is strikingly complete by 30 days. These facts suggest an urgency to understand cellular mechanisms producing muscle atrophy and weakness in the elderly. The long-term objective of this proposal is to gain a better understanding of factors impairing proliferation and differentiation of muscle progenitor cells during aging and physical inactivity, which accelerates muscle wasting during aging. As IGF-I rescues sarcopenia and the failure of muscle to regrow from immobilization in the old rats, Specific Aim 1 will extend these observations to cellular mechanisms. The general hypothesis of Specific Aim 1 is that IGF-I regulates the expression of p27Kip1, Gadd45, and MnSOD genes through nuclear FoxO1 levels in primary rat muscle progenitor cells of aging Fischer 344 x Brown Norway rats. A paradigm of medicine is to identify molecules responsible for pathologies to improve prevention and cures, which is one goal of Specific Aim 1. Specific Aim 2 will determine the roles that p53 and Sir2 play in impairing the proliferative and myogenic potential of muscle progenitor cells taken from skeletal muscles of old animals or from immobilized limbs of young and old animals. Overexpression and silencing of p53 and Sir2 will be employed to produce gain and loss of function, respectively. Specific Aim 3 will employ transcript profiling to identify previously unidentified mRNA differences in satellite cells, the side population of satellite cells, and differentiating myotubes at young, adult, I and old ages in order to provide novel candidate factors which can be tested for contributing to the differences l in cell behavior with aging. From the identified mRNAs, genes will be selected for cloning and functional l analysis to determine if their overexpression or silencing alters muscle cell phenotype in a manner consistent I with the aging phenotype. The outcomes of the research will provide a more scientific basis to devise therapies to prevent and treat sarcopenia and physical frailty.