Exercise promotes satellite cell contribution to myofibers in a load-dependent manner

Abstract

Background Satellite cells (SCs) are required for muscle repair following injury and are involved in muscle remodeling upon muscular contractions. Exercise stimulates SC accumulation and myonuclear accretion. To what extent exercise training at different mechanical loads drive SC contribution to myonuclei however is unknown. Results By performing SC fate tracing experiments, we show that 8-weeks of voluntary wheel running increased SC contribution to myonuclei in mouse plantar flexor muscles in a load-dependent but fiber type-independent manner. Increased SC fusion however was not exclusively linked to muscle hypertrophy as wheel running without external load substantially increased SC fusion in the absence of fiber hypertrophy. Due to nuclear propagation, nuclear fluorescent fate tracing mouse models were inadequate to quantify SC contribution to myonuclei. Ultimately, by performing fate tracing at the DNA level, we show that SC contribution mirrors myonuclear accretion during exercise. Conclusions Collectively, these findings provide direct evidence that mechanical load during exercise independently promotes SC contribution to existing myofibers.

Early satellite cell communication creates a permissive environment for long-term muscle growth

“…Cellular choreography early in response to stress, specifically with respect to extracellular matrix (ECM) deposition and inflammatory signaling, generally determines whether long-term homeostasis is properly restored (Adler et al, 2020). In skeletal muscle, Pax7+ satellite cells mediate myonuclear accretion during muscle fiber growth (Bachman et al, 2018; and in response to exercise irrespective of growth (Masschelein et al, 2020;Murach et al, 2020b). Satellite cells may also play an important role in muscle adaptation by regulating various cell types via secreted factors (Chazaud et al, 2003;Christov et al, 2007;Fry et al, 2014a;Patsalos et al, 2017;Tatsumi et al, 2009;Verma et al, 2018).…”

Morphological Changes in the Motor Endplate and in the Belly Muscle Induced by Previous Static Stretching to the Climbing Protocol

“…Masschelein et al (2020) reported that satellite cell fusion in the myofibers has characteristics that are load-dependent. Therefore, the lower myofibers’ total NV observed in climbing suggests that this modality of training did not trigger intense satellite cell fusion.…”

Fusion and beyond: Satellite cell contributions to loading‐induced skeletal muscle adaptation

“…Satellite cells are responsive to endurance-type exercise in rodents and humans. [194][195][196][197][198][199] They can activate, often expand in number, and sometimes fuse independent from hypertrophy [200][201][202][203] ; however, a degree of muscle damage with unaccustomed endurance exercise may obscure how satellite cells contribute to the adaptive response to endurance training. 63 Satellite cell fusion as a consequence of unaccustomed exercise training in the absence of hypertrophy may be most attributable to damage-mediated satellite cell behavior.…”