Scale-Up Strategy Focused on Hydrodynamic Stress for Mammalian Cell Culture Established by a Dry-Wet Approach

Today, most recombinant protein drugs are produced by mammalian cells in a stirred-type bioreactor (BR). Although cell culture scale-up strategies have been extensively investigated, scale-up and switching BRs while maintaining comparable culture performance remains a challenging step. This is because the empirical correlations used to determine operating parameters are applicable only for limited situations using similar BRs across scales. In addition, a few small scale-down models (SSDMs) are able to evaluate cellular sensitivity to the shear environment of manufacturing-scale BRs. In this study, we focused on the hydrodynamic stress associated with agitation and developed an SSDM that generates high shear stress without undesirable secondary effects such as vortex formation and severe gas hold-up. In-house BRs with various scales and configurations were used for fed-batch culture of CHO-K1 cells, and their shear environment was characterized by computational fluid dynamics (CFD). Using the dry-wet approach, we found that average shear stress was well correlated with titer decrease as an indicator of culture performance. We also confirmed that the response to shear stress differs among cell lines, and that evaluation of the shear sensitivity of cells is accordingly a risk mitigation step that is required to ensure successful scale-up.