Morphologic alteration of cultured arterial smooth muscle cells by cyclic stretching

Cyclic stretching of smooth muscle cells in culture resulted in a two- to fivefold increase in protein and collagen synthesis. The same in vitro system was utilized to relate changes in smooth muscle cell morphology to mechanical stress. Smooth muscle cells, grown in culture from rabbit aorta explants, were transferred to purified elastic membranes derived from bovine aorta. The membranes were either subjected to stretching and relaxation 52 times per minute or stretched and held stationary for 8, 48, or 56 hr. Profiles of rough endoplasmic reticulum (RER) were counted and myofilament content estimated from electron micrographs of 100 cells for each experiment. Cells from cyclically stretched preparations were compared with stationary cells derived from the same subculture. Myofilaments were largely replaced by RER in cyclically stretched cells and there was a reciprocal relationship between RER and myofilament content in individual cells. In cells from stationary preparations, myofilament content also diminished with time but RER profiles were few. At 56 hr, RER profiles numbered 16.7 +/- 1.7 in stretched cells compared with 3.6 +/- 1.3 in stationary cells (P less than 0.05). Cyclically stretched cells formed numerous intercellular contacts and showed little evidence of cytoplasmic degradation while stationary cells showed few contacts and contained numerous cytosomes and lamellar bodies. The results suggest that cyclic stretching resulted in the formation of RER or the preservation of myofilaments and that immobility resulted in the disappearance of myofilaments and cytoplasmic degradation.(ABSTRACT TRUNCATED AT 250 WORDS)