Fibronectin inhibits morphological changes in cultures of vascular smooth muscle cells

In culture, vascular smooth muscle cells proliferate until they form a confluent sheet of cells. At that time the morphology of the culture becomes altered and the cells form multilayered regions that eventually develop into nodular aggregations. We now demonstrate that the transition from monolayer culture to nodular culture is influenced by the presence of components in conditioned media. The development of nodules is enhanced by conditioned medium made from nodular cultures but is either inhibited or unaffected by monolayer culture-conditioned medium. Examination of the two types of conditioned media using NaDodSO4- polyacrylamide gels reveals many similarities and one major difference. Nodular-conditioned medium contains a prominent 42 kilodalton polypeptide which is not present in monolayer-conditioned medium. Further, we demonstrate that although both nodular and monolayer cultures produce fibronectin the transition to nodular culture does not occur in the presence of exogeneously added plasma fibronectin.