Deposition of stromal and basal laminal matrix by human amnion epithelial cells

In placental membranes near gestational term, amnion epithelial cells interact with a highly convoluted basal lamina beneath which is an acellular 'compact layer' of collagenous stroma rich in type III collagen. We have examined this extracellular matrix by SEM after fractioning the tissue or removing the epithelial cells enzymically, by TEM and by immunofluorescence with antibodies to matrix macromolecules. Matrix deposited by cultures of amnion epithelial cells has also been examined using these techniques as well as by SDS-PAGE. The principal conclusion is that both in vivo and in vitro, the cells deposit stromal as well as basal laminal macromolecules: collagen types I, III and IV, fibronectin and laminin. In addition, numerous other poorly characterised components are present. The matrix is not constricted in vitro as it is in tissue, suggesting the requirement during deposition for an organising template. In vivo the cells initially secrete matrix components into basal surface invaginations which occur between hemidesmosomes. Stromal matrix then appears to be assembled through gaps in the basal lamina.