Epithelial cell-cell and cell substrate contacts.

An epithelial sheet maintains its normal morphology by an appropriate balance between cell to cell and cell to substrate contacts which must be adjusted as proliferation occurs. We review our studies which attempts to analyze some of these problems by recombining cell and matrix tissue components, or by analyzing developmental changes in intact tissue. Epithelial and mesenchymal cells placed on tissue matrices which have been denuded of their normal tissue components behave distinctively, suggesting that this procedure could reveal inherent differences. When chick epiblast is grown on the outer surface of the vitelline membrane, the mode of expansion changes from that seen in the normal site, the vitelline membrane inner surface. Dispersed skin and corneal cells studied during subsequent aggregation show that one cell can influence desmosome formation in another. Finally, recent studies on developing chick liver indicate a correlation between the percent of lateral cell surface in the junctional domain and the proliferative rate of these cells.