Figure 1

Addition and removal of Y-27632 during long-term culture. A. Growth rate of three strains of foreskin keratinocytes from different donors cultured for at least 180 days in the presence or absence of 10 μM Y-27632. Cells cultured with Y-27632 continued to proliferate logarithmically (arrows) while untreated cells senesced at the times indicated by X. B. Y-27632 was removed from the three strains of keratinocytes cultured in its presence at pass 17. The subsequent growth curves are indicated in purple and senescence is indicated by X. C. Y-27632 was removed from the three strains of keratinocytes cultured in its presence at pass 23. The subsequent growth curves are indicated in purple and senescence is indicated by X. D. Y-27632 was added to keratinocyte strain 2 at pass 10. The resulting growth curve is shown in purple. In the inset, all three strains were cultured after cryogenic storage with Y-27632 added at pass 13 or 15 (as indicated). The resulting growth curves are shown. E. Y-27632 was added to keratinocyte strains at pass 19. The resulting growth curves are shown in purple.