Figure 1. Representative phase-contrast micrographs of cells. A-C: SLO+ corneal epithelial cell extract-induced cells (p-Pc) P1 (day 8), P3 (day 12), P5 (day 14); D-F: cells without any treatment (b-Pc) P1 (day 3), P3 (day 9), P5 (day 14); G-I: SLO+ES cell extract-induced cells (e-Pc) P1 (day 8), P3 (day 12), P5 (day 14); J-L: e-Pc P9 (wk 4), P12(wk 6), P18 (wk 8). The magnification of panel E is 50×, the other panels are at 100×. The three groups maintained similar morphology at P1 (day 8; A, D, and G). Some fibroblast-like cells took place in p-Pc group (B and C). The P3 cells in b-Pc control exhibited aging appearance with vacuoles and larger size, and could not survive through P5 (E and F). At P3 (day 14) of e-Pc, among the aging epithelial cells, colonies with small cells and vague boundaries showed up (H). At P5 (week 3), colonies that closely resembled to mES colonies could be readily identified by their morphology (I). This phenomenon was maintained for at least 14 weeks in culture, corresponding to 26 passages, but the colonies gradually became flat (J-L).