Effect of suspension time on growth potential in cryopreservation process of human mesenchymal stem cells

To establish a stable process with an acceptable quality of product, the reduction of variation is required. The cell bank production is one of the model for a decrease of fluctuation by evaluating the cells' viability and proliferation. Focusing on the dispensing process, a large volume of cell suspension in a cryoprotectant takes a long time to be transferred to cryovials. The aim of this study is to investigate the effect of suspension time and cryopreservation on the cell state and the cell potential of human mesenchymal stem cells using a conventional cell counting technique. When the cells were suspended in the cryoprotectant for 0, 1, 2 and 4 h, the reduction of the survival ratio (from unity value to 0.46 ± 0.03) and recovery ratio (from 0.75 ± 0.04 to 0.41 ± 0.09) was caused by the time dependent and time delayed effects. After that the cells were thawed and cultured to determine the cell potential which the attachment efficiency significantly decreased from 0.79 ± 0.04 to 0.39 ± 0.02 but the specific growth rate was constant, between (1.72 ± 0.26) × 10^-2 to (2.11 ± 0.24) × 10^-2 h^-1. Hence, this conventional quantification method can be achieved as a tool for evaluating the cell state and cell potential in mesenchymal stem cells. No threshold regarding in the suspension time was observed. As a result, the operation should be completed at the earliest convenience in the dispensing process. In addition, the changes of the cell state and the cell potential were caused by the time dependency and time delayed effects of the suspension time and the stress from the dispensing and the cryopreservation processes.