Sambasivan Ramkumar, Tajbakhsh Shahragim
Institute for Stem Cell Biology and Regenerative Medicine, GKVK, Bellary Road, Bangalore, 560065, India,
Results Probl Cell Differ. 2015;56:191-213. doi: 10.1007/978-3-662-44608-9_9.
Skeletal muscles in vertebrates have a phenomenal regenerative capacity. A muscle that has been crushed can regenerate fully both structurally and functionally within a month. Remarkably, efficient regeneration continues to occur following repeated injuries. Thousands of muscle precursor cells are needed to accomplish regeneration following acute injury. The differentiated muscle cells, the multinucleated contractile myofibers, are terminally withdrawn from mitosis. The source of the regenerative precursors is the skeletal muscle stem cells-the mononucleated cells closely associated with myofibers, which are known as satellite cells. Satellite cells are mitotically quiescent or slow-cycling, committed to myogenesis, but undifferentiated. Disruption of the niche after muscle damage results in their exit from quiescence and progression towards commitment. They eventually arrest proliferation, differentiate, and fuse to damaged myofibers or make de novo myofibers. Satellite cells are one of the well-studied adult tissue-specific stem cells and have served as an excellent model for investigating adult stem cells. They have also emerged as an important standard in the field of ageing and stem cells. Several recent reviews have highlighted the importance of these cells as a model to understand stem cell biology. This chapter begins with the discovery of satellite cells as skeletal muscle stem cells and their developmental origin. We discuss transcription factors and signalling cues governing stem cell function of satellite cells and heterogeneity in the satellite cell pool. Apart from satellite cells, a number of other stem cells have been shown to make muscle and are being considered as candidate stem cells for amelioration of muscle degenerative diseases. We discuss these "offbeat" muscle stem cells and their status as adult skeletal muscle stem cells vis-a-vis satellite cells. The ageing context is highlighted in the concluding section.
脊椎动物的骨骼肌具有惊人的再生能力。一块被挤压的肌肉能够在一个月内完全实现结构和功能上的再生。值得注意的是，在反复受伤后，高效的再生仍会持续发生。急性损伤后需要数千个肌肉前体细胞来完成再生。已分化的肌肉细胞，即多核收缩性肌纤维，终末退出有丝分裂。再生前体细胞的来源是骨骼肌干细胞——与肌纤维紧密相关的单核细胞，即卫星细胞。卫星细胞处于有丝分裂静止或慢周期状态，致力于肌生成，但未分化。肌肉损伤后微环境的破坏导致它们从静止状态退出并向分化方向发展。它们最终停止增殖，分化并融合到受损的肌纤维中或形成新的肌纤维。卫星细胞是研究充分的成年组织特异性干细胞之一，并且已成为研究成体干细胞的优秀模型。它们还成为衰老与干细胞领域的一项重要标准。最近的几篇综述强调了这些细胞作为理解干细胞生物学模型的重要性。本章首先介绍卫星细胞作为骨骼肌干细胞的发现及其发育起源。我们讨论调控卫星细胞干细胞功能的转录因子和信号线索以及卫星细胞池中的异质性。除了卫星细胞外，已证明许多其他干细胞也能生成肌肉，并且正被视为改善肌肉退行性疾病的候选干细胞。我们讨论这些“另类”肌肉干细胞及其作为成年骨骼肌干细胞相对于卫星细胞的地位。结论部分强调了衰老背景。
