Current Progress and Challenges for Skeletal Muscle Differentiation from Human Pluripotent Stem Cells Using Transgene-Free Approaches

Figure 1

Skeletal muscle differentiation in vitro. The terminal differentiation starts when Pax3⁺ and/or Pax7⁺ progenitors begin to express Myf5 or MyoD as committed myoblasts. These myoblasts gradually express myogenin (MyoG) and form single-nucleated nascent myotubes with myosin heavy chain (MHC⁺). Insulin-like growth factor-I (IGF-I), TGF-β1 inhibitor, and myostatin inhibitors induce myotube fusion to form multinucleated myotubes. Actin, myosin, and elastic myofilaments are arranged to form organized sarcomeres within the myotubes. Organized sarcomere structures give rise to a striated pattern in the myotubes and represent the functional contraction unit of muscles.