Derivation and properties of platelet-derived growth factor-independent rat smooth muscle cells

The present study reports that smooth muscle cells can be derived from the adult rat aorta without being exposed to serum containing platelet releasate, these cells can also be grown and passaged in medium lacking detectable quantities of platelet-derived growth factor (PDGF). As reported earlier, smooth muscle cells grown from the newborn or injured vessels have a distinctive epithelioid appearance. The platelet factor independent smooth muscle cells have a similar appearance. Unlike the cells from newborn animals or from injured vessels, smooth muscle cells derived in this way from the adult animal do not produce PDGF, although they do display PDGF receptors. Studies in serum-free medium show that the PDGF-independent cells can respond to PDGF when all other components of serum are absent; however, growth of these smooth muscle cells proceeds equally well in low concentrations of serum, independent of the presence of PDGF or other growth factors detectable by growth-promoting assays using either 3T3 cells or smooth muscle cells whose growth is dependent on factors present in whole blood serum. Taken together with recent observations in vivo, these data suggest that growth of at least some smooth muscle cells may depend on mechanisms independent of release of growth factors by platelets.