Longitudinal growth of skeletal myotubes in vitro in a new horizontal mechanical cell stimulator

A new computerized mechanical cell stimulator device for tissue cultured cells is described which maintains the cells in a horizontal position during mechanical stretching of up to 400% in substratum length. Mechanical stimulation of myogenic cells in this device initiates several aspects of in vivo skeletal muscle organogenesis not seen in normal static tissue culture environments. Embryonic skeletal muscle cells from avian m. pectoralis are grown in the device attached to the collagen-coated elastic substratum. Dynamic stretching of the substratum in one direction for 3 d at a rate (0.35 mm/h) that stimulates in vivo bone elongation during development causes the myoblasts to fuse into parallel arrays of myotubes which are 2 to 4 times longer than myotubes grown under static culture conditions. This longitudinal myotube growth is accompanied by increased rates of cell proliferation and myoblast fusion. Prestretching the collagen-coated substratum before cell plating also results in increased cell proliferation, myotube orientation, and longitudinal myotube growth. The effects of substratum stretching on myogenesis in this model system thus occur by alterations in the cell's extracellular matrix and not by acting directly on the cells.