Kinetics on aggregate behaviors of human induced pluripotent stem cells in static suspension and rotating flow cultures

Understanding of kinetics on aggregate behaviors of human induced pluripotent stem cells (hiPSCs) is critical knowledge for culture design because aggregate behaviors are considered to affect cell growth. In this study, we elucidated kinetics on aggregate behaviors of two types of hiPSCs (253G1 and 201B7 lines) to clarify the influence of aggregate behaviors on cell growth by comparing aggregate morphology, size of cell aggregates, and kinetic parameters in 72 h culture under static and floating conditions, which were realized by multi-dimple plate and rotating wall vessel, respectively. In the case of 253G1 line under floating condition, aggregate number decreased and size increased drastically during culture time, t = 0–24 h due to coalescence between cell aggregates. The apparent specific growth rate decreased after t = 24 h although cell number and aggregate size gradually increased under static condition. In the case of 201B7 line under floating condition, cell and aggregate number, and aggregate size kept constant levels during t = 24–72 h due to collapse of cell aggregates by stripping of single cells from aggregate, suggesting that specific death rate increased after t = 24 h despite constant levels of apparent specific growth rate and aggregate number under static condition. Our kinetic analysis concluded that excessive increase of aggregate size due to coalescence and cell death due to collapse critically affected growth of hiPSCs in suspension culture.