Fig. 8.

Diagram of the role of vitamin D on muscle growth and differentiation. During development, mesodermal stem cells become committed to the myogenic fate. Muscle precursors (myoblasts) remain in a proliferative state until they exit from the cell cycle and are instructed to differentiate. Differentiation is accompanied by cell fusion, where committed myoblasts become polynucleated myotubes. 1,25-D3 decreases cell proliferation and enhances myogenic cell differentiation by modulating the expression of key pro- and antimyogenic factors, such as IGF-I, IGF-II, Fst, and Mstn.