Vitronectin: effects on keratinocyte motility and inhibition of collagen-induced motility

Epibolin, a plasma protein, was initially purified on the basis of its ability to enhance spreading of keratinocytes. It is now known that epibolin is identical to serum spreading factor, S protein, and vitronectin, and the current name for the protein is vitronectin. Studies of vitronectin on cultured keratinocytes showed that it caused spreading and epiboly but not cellular adhesion to the substratum. In studies with other types of cells, vitronectin increased migration of several types of cells in a Boyden chamber. Because some agents that enhance spreading and adhesion, such as collagen and fibronectin, also increase motility, we tested whether vitronectin increased motility of keratinocytes. By photographing and quantitating motility of keratinocytes plated on a bed of colloidal gold particles, we determined that vitronectin increased local movement of keratinocytes in a concentration-dependent fashion, resulting in clearing of gold particles in a circular pattern around the cells, but did not cause the production of tracks found in cultures plated on collagen or fibronectin. The small increases in clearing of the gold particles that occurred in the presence of vitronectin were abolished by antibody to vitronectin. Furthermore, the marked increase in motility produced by type I collagen was significantly reduced when the keratinocytes were treated with vitronectin. Antibody to vitronectin also abrogated the vitronectin-induced reduction in collagen-stimulated motility, confirming that this action was specific for vitronectin. Serum, which contains vitronectin, stimulated motility in a fashion identical to purified vitronectin, but serum lacking vitronectin was inactive. These studies show that vitronectin causes a localized increase in movement associated with spreading resulting in a halo around individual cells, that vitronectin does not enhance directional motility of keratinocytes in this assay but in contrast antagonizes such motility produced by collagen, and that vitronectin is the factor in serum responsible for this effect. The findings with vitronectin and collagen show that these agents stimulate different types of motility. The roles in wound healing of agents stimulating different types of motility are unclear and require further study.