Mammalian cell culture synchronization under physiological conditions and population dynamic simulation.

The overall behavior of cell cultures is determined by the actions and regulations of all cells and their interaction in a mixed population. However, the dynamics caused by diversity and heterogeneity within cultures is often neglected in the study of cell culture processes. Usually, a bulk behavior is assumed, although heterogeneity prevails in most cases. It is, however, not valid to conclude from the bulk behavior to the single cell behavior. Instead, it is necessary to include the behavior and kinetics of subpopulations and their interactions into models in order to elucidate the dynamic effects occurring in typical cell cultures. Heterogeneity in cell cultures is largely caused by the progress of the cell cycle. Cell cycle-dependent dynamics resulting for example in variable transfection efficiencies or expression bistability have recently attracted attention. In order to elucidate cell cycle-dependent regulations in cell cultures, it is desirable to synchronize a culture with minimal perturbation, which is possible with different yield and quality using physical methods, but not possible for frequently used chemical, or whole-culture methods. Then, the culture is cultivated again under physiological conditions and subpopulation-resolved analysis and modeling approaches are applied. This should allow to account for the variable contributions of subpopulations to the whole behavior and also for obtaining hereto unaccessible dynamic information of cellular regulation. In this short review, we summarize techniques and key issues to be considered for successful synchronization, cultivation, and modeling in order to achieve the goal of better understanding cell culture at a population level.