Migration mechanisms: corneal epithelial tissue and dissociated cells

The migratory mechanism of intact bovine corneal epithelial tissue and individual corneal epithelial cells over synthetic surfaces in vitro were compared. In migrating tissue, adhesion between component cells was demonstrated by immunostaining for desmoplakin and identification of desmosomes by electron microscopy. The apparent intermeshing of microtubules within the tissue and interdigitation of cytoplasmic membranes showed the close association of cells. Portions of the advancing edge of the tissue contained actin filaments that were orientated parallel to the leading tissue front. These filaments appeared to span adjacent cells suggesting that migration partially involved the contraction of the actin cable, similar to the 'purse-string' mechanism originally identified in the closure of fetal skin wounds. Intact actin filaments and microtubules were necessary to maintain optimum migration rates for tissue and cells. However, tissue morphology was not dependent on microtubule integrity. During the migration of individual epithelial cells, no staining for desmoplakin was observed and there were clear divisions between the microtubules of adjacent cells. Actin filaments tended to be arranged parallel to the direction of cell movement.Therefore, migration of epithelial tissue sheets over synthetic surfaces occurs by mechanisms that differ from the migration of individual epithelial cells. Model systems based on the migration of intact tissue would give a more realistic assessment of the suitability of a material for biomaterial applications than the use of separate epithelial cells.