Role of extracellular matrix in age-related declines of muscle regeneration

摘要 由损伤或手术引起的骨骼肌损伤通常会导致显著的功能衰退 在老年人身上。这些下降至少部分归因于肌肉愈合失败。肌肉再生是 主要由肌肉干细胞或“卫星”细胞(MuSCs)的活动决定，MuSCs是一种储备细胞群， 随着年龄的增长，典型地表现出相当大的功能障碍。根据干细胞的“利基” 干细胞的反应在很大程度上是由生物物理和生化线索决定的，这些线索源于 周围的微环境。事实上，扩大对微环境对 干细胞的行为导致了最近生物灵感和工程化细胞外细胞外的发展 治疗骨骼肌损伤的基质(ECM)方法。然而，仍然缺乏深入的 了解本土ECM的致病教学特征是否以及如何扰乱MUSC 功能和骨骼肌再生。而很明显，MUSC的激活、自我更新、增殖 和分化受到物理和动态生态位相互作用的影响，这是对 与年龄相关的细胞外基质改变对骨骼肌再生能力的直接影响尚不清楚。 这个项目的总体目标是测试我们的中心假设，即与年龄相关的生物物理学 骨骼肌细胞外基质的改变促进了MSC的纤维化转化，最终推动了 骨骼肌再生受损。此外，我们假设这些致病生物物理 变化可以通过机械刺激恢复，至少部分恢复。为了实现这一目标，我们将 采用包含尖端超分辨率成像和3-D组织的集成方法 解决两个具体目标的工程方法。目标1研究将测量、操纵和模拟 青年和老年骨骼肌细胞外基质的生物物理特性研究 对MUSC命运的建筑和弹性ECM修改。目标2研究将确定通过哪些机制 机械刺激调节老年ECM的生物物理性质以促进MUSC的肌原性和 肌肉再生。这些目标的成功实现将加深我们对1) 原生ECM在MUSC谱系规范方面的指导能力，2)这些指导能力如何 能力随着时间的推移而变化，以及3)控制骨骼衰老的分子机制 肌肉再生潜力。综上所述，成功完成这些研究可能会提供一个 用于治疗老年人骨骼肌损伤的新型ECM靶点的确定基础 人口。更广泛地说，更深入地了解与年龄相关的生物力学变化， 架构和动态ECM属性直接MUSC功能将扩展我们对 衰老和干细胞生物学。

ABSTRACT Skeletal muscle trauma resulting from an injury or surgery often results in significant functional declines in older adults. These declines are at least partially attributed to failed muscle healing. Muscle regeneration is predominantly dictated by the action of muscle stem, or “satellite”, cells (MuSCs), a reserve cell population that typically demonstrates considerable dysfunction with increasing age. According to the stem cell “niche” concept, stem cell responses are largely determined by biophysical and biochemical cues that emanate from the surrounding microenvironment. Indeed, expanding recognition of the influence of the microenvironment on stem cell behavior has led to a recent surge in the development of bioinspired and engineered extracellular matrix (ECM) approaches for the treatment of skeletal muscle injuries. Still lacking, however, is an in-depth knowledge of whether and how pathogenic instructional characteristics of the native ECM disrupt MuSC function and skeletal muscle regeneration. While it is evident that MuSC activation, self-renewal, proliferation and differentiation are influenced by physical and dynamic niche interactions, a mechanistic understanding of the direct impact of age-related ECM alterations on skeletal muscle regenerative capacity is unknown. The over-arching goal of this project is to test our central hypothesis that age-related biophysical alterations in the skeletal muscle ECM promotes a fibrogenic conversion in MuSCs, ultimately driving impaired skeletal muscle regeneration. Further, we hypothesize that these pathogenic biophysical changes may be reverted, at least partially, by mechanical stimulation. To achieve this goal, we will employ an integrated approach that encompasses cutting-edge super-resolution imaging and 3-D tissue engineering methods to address two specific aims. Aim 1 studies will measure, manipulate, and mimic the biophysical properties of young and aged skeletal muscle ECM in order to dissect the effect of age-related architectural and elastic ECM modifications on MuSC fate. Aim 2 studies will identify mechanisms by which mechanical stimulation modulates biophysical properties of the aged ECM to promote MuSC myogenicity and muscle regeneration. Successful achievement of these aims will further our understanding of 1) the instructional capabilities of the native ECM on MuSC lineage specification, 2) how these instructional capabilities change over time, and 3) the molecular mechanisms controlling age-related declines in skeletal muscle regenerative potential. Taken together, successful completion of these studies may provide a foundation for the identification of novel ECM targets in the treatment of skeletal muscle injuries for a geriatric population. More broadly, an improved insight into how age-associated alterations in biomechanical, architectural and dynamic ECM properties direct MuSC function will expand our fundamental understanding of aging and stem cell biology.