Smooth muscle releases an epithelial cell scatter factor which binds to heparin

Abstract

We report that cultured bovine calf aorta and human adult iliac artery smooth muscle cells release a soluble factor which causes spreading and separation of cells in normally tight, cohesive epithelial colonies, similar to the morphologic changes induced by the fibroblast-derived scatter factor (SF). Smooth muscle-derived SF was heat sensitive, trypsin labile, and nondialyzable, consistent with a protein (or proteins). Its effects on epithelium were not mimicked by a variety of proteolytic enzymes, growth factors, or hormones, and were not blocked by antiproteases or by antibodies to fibronectin and basic fibroblast growth factor. Epithelial cell proliferation was unaffected or only mildly stimulated by partially purified SF at concentrations that produced cell scattering. Both smooth muscle- and MRC5 human embryo fibroblast-derived SFs could be partially purified with similar elution patterns on a number of different chromatographic columns, including DEAE-agarose, heparin-sepharose, Bio-Rex 70, concanavalin A-sepharose, and MonoQ. SF from both sources bound tightly to heparin-sepharose, requiring 1.3 to 1.4 M NaCl for elution. The morphologically obvious cell scattering effect was markedly inhibited by soluble heparin at concentrations down to 5 micrograms/ml, and this inhibition was prevented by protamine. These data suggest that vascular smooth muscle cells produce an epithelial cell scattering factor with properties similar to the fibroblast-produced factor, including a high affinity for heparin. Such factors are potentially important because they may represent a new class of proteins that primarily regulate cell mobility rather than growth and differentiation.