Signaling satellite-cell activation in skeletal muscle: markers, models, stretch, and potential alternate pathways.

Activation of skeletal muscle satellite cells, defined as entry to the cell cycle from a quiescent state, is essential for normal growth and for regeneration of tissue damaged by injury or disease. This review focuses on early events of activation by signaling through nitric oxide and hepatocyte growth factor, and by mechanical stimuli. The impact of various model systems used to study activation and the regulation of satellite-cell quiescence are placed in the context of activation events in other tissues, concluding with a speculative model of alternate pathways signaling satellite-cell activation.