Basal cell adhesion to a culture substratum controls the polarized spatial organization of human epidermal keratinocytes into proliferating basal and terminally differentiating suprabasal populations.

The contribution of adhesion to an extracellular matrix in the polarized spatial organization of keratinocytes was studied in dispase-detached cultures stored as floating sheets. Proliferating and terminally differentiating cell populations were, therefore, localized on tissue sections by their DNA-synthesizing ability and involucrin immunostaining, respectively. A progressive reorganization was induced from superposed proliferating and differentiating layers into clusters exhibiting differentiating cells on the outside. Measurements of proliferation and terminal differentiation in detached cultures revealed the progressive disappearance of proliferating cells, followed by an increase in involucrin-positive cells. Attempts to block the spatial reorganization by the addition of components of the extracellular matrix remained unsuccessful. These results suggest that basal anchorage is responsible for the superposition of proliferating and differentiating cells in keratinocyte cultures. They afford new arguments for the induction of terminal differentiation in non-adhesive keratinocytes which exhibit a concomitant modification of cell shape.