Muscle Satellite Cell Pool During Aging

描述（由申请人提供）：有效的组织修复依赖于器官控制干细胞或组织特异性祖细胞的数量和功能的能力。卫星细胞（SCs）是成人骨骼肌修复的“首选细胞”。基于所有体细胞（包括SCs）都具有有限容量的假设；在保持内在容量不变的情况下减少池内SCs的数量将导致最终的功能衰竭和肌肉修复受损。同样，如果内在能力受损，而维持池中SCs的数量，这也会导致肌肉功能的不利结果。在衰老过程中，肌肉再生能力明显受损。这与SC数量和功能的下降相吻合。年龄相关的肌肉再生损伤是否由SC数量和/或功能的损失引起，目前仍未得到解决。该提案的第一部分侧重于了解SC池在整个生命中的异质性，以及SC亚群是否具有“抗衰老性”。我们将使用一种新的绿色荧光蛋白报告器，它允许在体内逐个细胞的基础上确定增殖输出。将测试慢速和快速分裂SCs的功能多样性。这一目标将回答衰老是否与SCs特定功能亚群的丧失有关。提案的第二部分侧重于研究池中可用SCs数量对有效修复的重要性。我们将系统地减少成人和老年肌肉中的SC数量，以询问：1)SC数量的下降是否会导致再生受损，2)限制SC数量引起的强制增殖需求是否会迫使SC过早衰竭。这一目标将实现使用新的遗传策略，使SC特异性细胞消融。该提案的第三部分侧重于SC有效修复肌肉的内在能力，特别是P16INK4A作为衰老过程中SC祖细胞增殖和谱系进展的调节剂的作用。P16INK4A是一种衰老生物标志物，与衰老组织的再生损伤有关。P16INK4A在肌发生中的作用以前没有被研究过。最后，通过结合SC消融技术和P16INK4A功能缺失方法，我们将探讨SC数量和功能之间的相互作用，以实现有效的组织修复。了解SCs数量和内在容量之间的协调关系对于治疗肌肉减少症和其他肌肉退行性病变至关重要。该提案的具体目的是：1)研究SC池的异质性，因为它与整个生命中的增殖性输出有关；2)确定增殖性输出是否与肌肉减少症有因果关系；3)研究通过P16INK4A功能缺失方法对SC功能的遗传操纵对年轻和老年肌肉有效修复的影响。

DESCRIPTION (provided by applicant): Effective tissue repair relies on an organs ability to control the number and function of stem cells or tissue specific progenitors. Satellite cells (SCs) are the "cell of choice" for adult skeletal muscle repair. Based on the assumption that all somatic cells, including SCs, have a finite capacity; reducing the number of SCs within the pool while keeping intrinsic capacity unchanged will lead to eventual functional exhaustion and impaired muscle repair. Similarly, if intrinsic capacity is impaired, while the number of SCs in the pool is maintained, this will also lead to a detrimental outcome for muscle function. During aging, muscle regeneration capacity is significantly impaired. This coincides with a decline in SC number and function. It remains unresolved whether age related impairment in muscle regeneration is caused by a loss in SC number and/or function. The first part of the proposal focuses on understanding the heterogeneity within the SC pool throughout life, moreover whether subsets of SCs are 'age-resistant. We will use a novel GFP reporter that allows proliferative output to be determined on a cell-by-cell basis in vivo. Slow and fast dividing SCs will be tested for functional diversity. This aim will answer whether aging is associated with a loss of specific functional subpopulations of SCs. The second part of the proposal focuses on studying the importance of the number of SCs available in the pool for effective repair. We will systematically decrease the number of SCs within adult and aged muscle to ask, 1) whether a decline in SC number causes impaired regeneration, 2) whether forced proliferative demand induced by limiting the number of SCs forces premature SC exhaustion. This aim will be achieved using novel genetic strategies that enable SC specific cell ablation. The third part of the proposal focuses on the intrinsic capacity of SCs to effectively repair muscle, in particular the role of P16INK4A as a regulator of SC progenitor proliferation and lineage progression during aging. P16INK4A, an aging biomarker, has been implicated in regenerative impairment of aged tissue. The role of P16INK4A in myogenesis has not been studied previously. Finally by combining SC-ablation technology and P16INK4A loss-of-function approaches, the interaction between SC number and function for effective tissue repair will be interrogated. Understanding the coordination between the number and intrinsic capacity of SCs will be critical for treatment of sarcopenia and other muscle degeneration pathologies. The specific aims of this proposal are: 1) to study heterogeneity in the SC pool as it relates to proliferative output throughout life, 2) to determine if proliferative output is causally related to sarcopenia and 3) to study the effect of genetically manipulating SC function through P16INK4A loss-of-function approaches for efficient muscle repair in young and aged muscle.