[The effect of the duration of culturing on the pluripotency of mouse embryonic stem (ES) cells in vitro and in vivo].

A comparative analysis of two clones of mouse embryonic stem cells (ES-D3) that underwent different number of passages was performed to determine their potencies for in vitro and in vivo development. Cells of both clones had similar morphology characteristic of undifferentiated ES cells and were capable of forming embryoid bodies in the suspension cultures. Specific alkaline phosphatase activity of ES cells was revealed by cytochemical staining. Karyotyping showed that the proportion of aneuploid ES cells increases with an increase in the number of passages. The results of experiments on chimera production using ES cells showed that the clone D3W (passage 17) is superior to the clone D3M (passage 42) in terms of both the proportion of chimeras produced and the degree of coat color chimerism in them.