Muscle Satellite Cell Pool During Aging

描述(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前体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，包括干细胞，都具有有限的能力的假设；在保持固有能力不变的情况下，减少池中的干细胞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，而池中干细胞的数量保持不变，这也将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数量和功能的下降不谋而合。肌肉再生中的年龄相关性损伤是否由SC数量和/或功能的丧失引起，目前尚无定论。该提案的第一部分集中于了解SC池中的异质性，以及SC的子集是否具有抗年龄特性。我们将使用一种新的绿色荧光蛋白报告程序，它允许在活体内逐个细胞地确定增殖输出。将对慢速和快分SC进行功能多样性测试。这一目标将回答衰老是否与干细胞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SC的数量对有效维修的重要性。我们将系统地减少成年和老年肌肉中的干细胞数量，以问：1)干细胞数量的减少是否会导致再生受损，2)限制干细胞数量所产生的强迫增殖需求是否会迫使SC过早耗尽。这一目标将通过使用新的遗传策略来实现，这种策略能够使干细胞特异性细胞消融。该提案的第三部分侧重于干细胞有效修复肌肉的内在能力，特别是P16INK4A在衰老过程中作为干细胞祖细胞增殖和谱系进展的调节因子的作用。P16INK4a是一种衰老生物标志物，与衰老组织的再生损伤有关。P16INK4A在肌肉发生中的作用以前还没有研究过。最后，通过结合干细胞消融技术和P16INK4A功能丧失方法，将探讨干细胞数量和功能之间的相互作用，以实现有效的组织修复。了解干细胞数量和内在能力之间的协调关系对于治疗骨质疏松症和其他肌肉退行性病变至关重要。这项建议的具体目的是：1)研究干细胞池中的异质性，因为它与终生的增殖输出有关；2)确定增殖输出是否与骨质疏松症有关；3)研究通过P16INK4A功能丧失途径对年轻和老年肌肉进行有效修复的基因调控SC功能的效果。 公共卫生相关性：破译肌肉再生过程中卫星细胞数量和功能之间的协调关系，对于利用它们的潜力治疗日益老龄化的人口中的骨骼减少至关重要。此外，成体卫星细胞的生物学可以作为干细胞在其他组织中的范例。

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. PUBLIC HEALTH RELEVANCE: Deciphering the coordination between satellite cell number and function during muscle regeneration is critical for harnessing their potential to treat sarcopenia in an increasingly aging population. Furthermore, the biology of adult satellite cells may serve as a paradigm for stem cells in other tissues.