Inserm, U1016, Institut Cochin, 24 Rue du Faubourg Saint Jacques, Paris, France.
Curr Top Dev Biol. 2011;96:121-38. doi: 10.1016/B978-0-12-385940-2.00005-X.
The fate of stem cell is regulated by cues received from the surrounding area. Recently, the concept of "stem cell zone"--rather than a predefined niche--introduced the notion of dynamic and permanent interactions between stem cells and their microenvironment. In adult skeletal muscle, satellite cells are considered as the main stem cells responsible for muscle repair and maintenance. They are localized close to vessels regardless their state of activation and differentiation. Moreover, the number of satellite cells is positively correlated to the capillarization of the myofiber. Angiogenesis has been known for a long time to be essential for muscle repair. However, relationships between vessel cells and satellite/myogenic cells that govern myogenic cell expansion, myogenesis, and angiogenesis have been only recently investigated. In this chapter, we discuss the possible existence of a vascular amplifying/differentiating niche, in an attempt to reconciliate several recent observations showing that satellite/myogenic cells interact with various cell types during the time course of muscle regeneration. Indeed, endothelial cells (ECs) stimulate myogenic cell growth and, inversely, differentiating myogenic cells promote angiogenesis. However, stromal cells may also provide some proliferating or differentiating cues to satellite/myogenic cells in this vascular area. Although some molecular effectors have been identified, including growth factors and cytokines, molecular regulations that occur within this vascular amplifying/differentiating niche requires further investigation. At the end of muscle repair, maturation of newly formed vessels takes place. In this context, we discuss the potential quiescence niche of satellite cells and the specific role of periendothelial cells. Indeed, periendothelial cells promote the return to quiescence of a subset of satellite/myogenic cells and maintain their quiescence (through Angiopoietin-1/Tie-2 signaling). We ask to what extent the environment may control the fate choice of satellite/myogenic cells and we also question the "hypoxic niche" in skeletal muscle, such a quiescence niche having being observed in the bone marrow.
干细胞的命运受到周围环境的影响。最近，“干细胞区”的概念（而不是预先确定的生态位）提出了干细胞与其微环境之间动态和永久相互作用的概念。在成年骨骼肌中，卫星细胞被认为是负责肌肉修复和维持的主要干细胞。它们位于血管附近，无论其激活和分化状态如何。此外，卫星细胞的数量与肌纤维的毛细血管化呈正相关。血管生成长期以来一直被认为对肌肉修复至关重要。然而，血管细胞与卫星/成肌细胞之间的关系，这些关系控制着成肌细胞的扩增、成肌和血管生成，最近才被研究。在这一章中，我们讨论了可能存在的血管扩增/分化生态位，试图调和最近的一些观察结果，这些观察结果表明卫星/成肌细胞在肌肉再生的过程中与各种细胞类型相互作用。事实上，内皮细胞（ECs）刺激成肌细胞的生长，而分化的成肌细胞则促进血管生成。然而，基质细胞也可能在这个血管区域为卫星/成肌细胞提供一些增殖或分化的线索。尽管已经确定了一些分子效应物，包括生长因子和细胞因子，但这个血管扩增/分化生态位内发生的分子调控仍需要进一步研究。在肌肉修复结束时，新形成的血管成熟。在这方面，我们讨论了卫星细胞的潜在静止生态位和周细胞的特定作用。事实上，周细胞促进了一部分卫星/成肌细胞的静止，并通过血管生成素-1/Tie-2 信号维持其静止。我们要问环境在多大程度上可以控制卫星/成肌细胞的命运选择，我们还质疑骨骼肌中的“缺氧生态位”，因为在骨髓中已经观察到了这种静止生态位。
