Cell stroma interactions in aortic endothelial cell cultures.

The behavior of bovine aortic endothelial cell cultures indicates that they interact with the extracellular materials they produce. In nonconfluent cultures the basal part of the cell is oriented on the plastic of the culture dish with the apex facing the culture medium. At confluence, fibrillar and ruthenium red-stained material, partly proteoglycan in nature, appears beneath the cells. In older cultures, a second layer of endothelial cells grows beneath the original one next to the plastic. This layer is oriented differently, being inverted in that the apex of the cells points to the plastic and the base toward secreted extracellular materials. Because of this orientation, cells tend to peel off the dish. The morphologic sequences thus suggest that polarity of endothelial cells in culture depends on its environment, with a hierarchy of polarity. In the absence of matrix materials, orientation is determined by the plastic. When extracellular materials form, endothelial cells then orient on them. Thus, the cells appear to manufacture and secrete the molecules on which their topography depends. Smooth muscle cells from the same bovine aortas do not seem to have this polarity. Glycosaminoglycans synthesized by the two cell types also differ.