Karyotypic Stability

The use of perfusion bioreactors, in which the medium is pumped through the culture vessel, has also been reported (Oh et al., 2005) for the expansion of mouse ESC lines on Petriperm (a Petri dish with a gas-permeable base). The cell densities obtained were 64-fold greater compared to Petri dish controls which only originate a nine-fold increase compared to the initial inoculum, over 6 days. The mESCs that were expanded retained pluripotency markers, had the ability to form derivatives of the three embryonic germ layers in teratomas, and maintained karyotypic stability. Perfusion cultures with cell retention ensure homogeneity of nutrient supplementation, inhibition of waste accumulation, and improved process reproducibility (Thomson, 2007). However, these cultures are still at a small-scale. 

Karyotypic analysis Oncogene screening Gene stability Infection DNA screens... 

Cultures of established cell lines or cell strains should be used. These should be determined to be mycoplasm free and should be karyotyped. To reduce the spontaneous frequency of the TK mutants, the cells should be cleansed, that is, exposed to conditions that inhibit this phenotype, then returned to normal growth media for a few days before the start of the study. The cells used are selected on the basis of growth ability in culture and stability of the spontaneous mutation frequency. 

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