Kinetic analysis of cell decay during the filling process: Application to lot size determination in manufacturing systems for human induced pluripotent and mesenchymal stem cells

Scale-up of a cell-manufacturing system involves an extension of the filling process time because of the increased number of vials to be filled with the cells suspended in a cryopreservation solution. As the solution includes cryoprotective agents such as dimethyl sulfoxide that is toxic to cells, a longer processing time has an adverse impact on the quality of cell products. Therefore, understanding the related cell-decay kinetics is a major challenge for the development of robust and scalable cell-manufacturing systems. In this study, a new set of performance indices were defined to quantify the state and potential of cells suspended in a cryopreservation solution, i.e., the survival ratio of cells suspended in cryopreservation solution was provided for the cell state estimation, and the recovery ratio of cells after freezing and thawing, the attachment efficiency of cells after seeding, and the specific growth rate of surviving cells were provided for the cell potential estimation. Using these indices, the time-dependencies of cell viability variation in human induced pluripotent (hiPSCs) and human mesenchymal stem cells (hMSCs) suspended in a cryopreservation solution were investigated. Based on the obtained kinetic data, strategies for developing and controlling cell-manufacturing systems were discussed.