Satellite cell dynamics during skeletal muscle hypertrophy

Abstract

Skeletal muscle stem cells (MuSCs) display distinct behavior crucial for tissue maintenance and repair. Upon activation, MuSCs exhibit distinct modes of division: symmetric division, facilitating either self-renewal or differentiation, and asymmetric division, which dictates divergent cellular fates. This review explores the nuanced dynamics of MuSC division and the molecular mechanisms governing this behavior. Furthermore, it introduces a novel phenomenon observed in a subset of MuSCs under hypertrophic stimuli termed division-independent differentiation. Insights into the underlying mechanisms driving this process are discussed, alongside its broader implications for muscle physiology.

Keywords: differentiation; division patterns; division-independent differentiation; hypertrophy; muscle stem cells; proliferation.

Figure 1.. Summary of muscle stem cell (MuSC) division dynamics.

(A) Upon activation by injury, MuSCs exhibit two distinct modes of division: (1) symmetric or (2) asymmetric. This process is intricately linked to the differentiation pathway. A dashed line represents a potential cell fate; a solid line represents a determined cell fate. (B) In response to a hypertrophic stimulus, (1) a subset of MuSCs differentiate and fuse with myofibers without undergoing cell division in response to hypertrophy (i.e., direct fusion). MuSCs can also undergo (2) symmetric or asymmetric proliferation for self-renewal and/or fusion. Same color MuSCs indicate symmetric division; different color MuSCs indicate asymmetric division; green color indicates the nucleus; red color within the nucleus indicates the presence of EdU.