Muscle Stem Cell and Physical Activity: What Point is the Debate at?

Abstract

In the last 15 years, it emerged that the practice of regular physical activity reduces the risks of many diseases (cardiovascular diseases, diabetes, etc.) and it is fundamental in weight control and energy consuming to contrast obesity. Different groups proposed many molecular mechanisms as responsible for the positive effects of physical activity in healthy life. However, many points remain to be clarified. In this mini-review we reported the latest observations on the effects of physical exercise on healthy skeletal and cardiac muscle focusing on muscle stem cells. The last ones represent the fundamental elements for muscle regeneration post injury, but also for healthy muscle homeostasis. Interestingly, in both muscle tissues the morphological consequence of physical activity is a physiological hypertrophy that depends on different phenomena both in differentiated cells and stem cells. The signaling pathways for physical exercise effects present common elements in skeletal and cardiac muscle, like activation of specific transcription factors, proliferative pathways, and cytokines. More recently, post translational (miRNAs) or epigenetic (DNA methylation) modifications have been demonstrated. However, several points remain unresolved thus requiring new research on the effect of exercise on muscle stem cells.

Keywords: Cardiac muscle; Physical exercise; Skeletal muscle; Stem cell.

Figure 1

Schematic representation of the effects of physical activity on skeletal muscle and heart. Panel A: muscle is shown like a cylinder with inside poly-nucleated fibers. Physical activity determines a morphological hypertrophy of muscle due to the increase in fiber numbers, in nuclei number per fiber and fiber size. Together with muscle hypertrophy, exercise induces proliferation of endothelial cells and release of proangiogenic and anti-angiogenic factors whose balance contributes to muscle adaptation to physical exercise. SC, Satellite Cells; Panel B: A schematic heart section is shown. Physical exercise determines cardiac hypertrophy (due to the increase of cardiomyocyte length, activation of cardiac stem cells and microvascular remodeling). RV, Right Ventricle; LV, Left Ventricle; IGF, Insulin Like Growth Factor 1; NRG-2, Neuregulin-2; NO, Nitric Oxide; CSCs, Cardiac Stem Cells; EPCs, Endothelial Progenitor Cells. In both panels, possible molecular mediators are reported.