Dynamic mechanical orientation of skeletal myofibers in vitro

Avian embryonic myoblasts respond to a continuously stretching substratum in vitro by fusing into skeletal myofibers which are oriented parallel to the direction of substratum movement. The rate of stretch is critical for optimal orientation to occur. A speed of 0.2 mm per hour gives optimal orientation and rates of stretch faster or slower than this decreases the percentage of oriented fibers. The ratio of the rate of myofiber development to the rate of substratum stretch for optimal in vitro myofiber orientation is comparable to the in vivo ratio of the rate of myofiber development to the rate of bone elongation. Thus, this in vitro system supports the idea that mechanical force may be an important element in morphogenesis of skeletal muscle.