Novel substratum-dependent dendritic morphology and motility in epithelial cells.
Qualitative and quantitative light microscopy including time-lapse observations, and scanning electron microscopy are applied to study the response of cultured primary amnion epithelial cells to surfaces coated with a fibronectin-containing aggregate extracted from placenta (PSF). Cell shapes are compared with those observed in medium containing serum and amniotic fluid. Cells respond rapidly to PSF in serum-free medium to give unusual dendritic structures. Cell bodies remain rounded with numerous long and complex processes appearing and disappearing over a period of 6 to 6 1/2 h. This behaviour is associated with an 18-fold increased motility relative to control cells. Few attachments to substratum occur beneath cell bodies or along dendritic processes, points of adhesion being largely confined to the termini of extensions. Later in the response to PSF, a reduction in cell extensions is accompanied by flattening of the cell body and more conventional shapes reminiscent of control cells are restored. In serum, cells spread more slowly to give well-flattened discoid or polygonal morphologies. In amniotic fluid, blebbed, bipolar and asymmetrical cells are observed with some dendritic extensions, reminiscent of those seen on PSF. The profound influence of substratum-associated ligands on cellular behavior is noted.