Heterogeneity and cell cycle analyses from time-lapse studies of human keratinocytes in vitro.

We have analysed the behaviour of cultured epidermal keratinocytes using time-lapse video recordings. We have found evidence for heterogeneity in the behaviour of the cells. Some lines underwent extensive self-renewal, thus expanding the population, while others produced daughter cells that migrated suprabasally and are presumed to have undergone terminal differentiation. We also present kinetic data on the cell cycle times, mitotic durations and post-mitotic residence times. The latter is the time between a cell's birth and eventual suprabasal migration. The data suggest that the 'decision' to migrate is in some way 'programmed' but that the actual migration is a stochastic process. Time-lapse analysis is a very powerful technique for lineage and cell kinetic analysis.