So-called satellite cells in muscle, known to be responsible for the growth, maintenance, and repair of skeletal muscle after birth, are not a homogeneous population of dedicated muscle progenitors as once thought, according to a team led by the Ottawa Health Research Institute. They are actually a mix of cells already committed to their muscular fate and others that behave like more versatile stem cells.
The scientists decided to take a closer look at the molecular profiles of satellite cells isolated from mouse muscle. They showed that the satellite cells consist of two classes defined by the activity or inactivity of the Myf-5 gene.
They found that this genetic difference gave rise to a distinction in the satellite cells’ behavior. Cells without active Myf-5 divide asymmetrically—a characteristic commonly seen among stem cells. That lopsided cell division produced one daughter like its parent, exhibiting a stem cell-like capacity for self renewal, and another Myf-5 positive cell.
The researchers also showed that satellite cells in which Myf-5 was switched on, when injected into the muscles of mice, continued down the road toward becoming muscle. In contrast, transplantation of Myf-5 negative cells contributed to the satellite cell reservoir throughout the injected muscle.
The report will appear in the June 1 issue of Cell.