(158z) Model-Based Assessment of Freezing Temperature Profiles for Human Induced Pluripotent Stem Cells

Human induced pluripotent stem (hiPS) cells are the emerging source of regenerative medicine products. Along with successful clinical studies, e.g., Parkinson’s disease or spinal cord injuries, the demand is increasing. It is now urgently necessary to establish freezing processes of the cells for storage and transportation. As the technique of freezing hiPS cells, slow freezing is considered more appropriate for commercial production than vitrification because of scalability, simplicity in operation, and no direct contact with liquid nitrogen. However, the design of slow freezing processes for hiPS cells is still empirical. Towards commercial production of hiPS cells, the temperature profile of a freezer, which would have a significant impact on both cell quality and productivity, need to be established.

This work presents model-based assessment of freezing temperature profiles for hiPS cells. We developed a single-cell model by integrating models describing a temperature profile in a container, cell volume change through transmembrane transport, intracellular ice formation, and cell survival rate after thawing. This is an extension of our previously presented mechanistic model of single-cell freezing¹. Freeze/thaw experiments of hiPS cells were performed using a programmable deep freezer in order to estimate model parameters. The objective functions were defined as the cell survival rate after thawing and the required freezing time which were the cell quality and the productivity objectives, respectively. Given the temperature profile, the developed model can produce the survival rate and the freezing time.

Using the single-cell model, we conducted the assessment of over 10,000 different temperature profiles for a programmable deep freezer using the single-cell model. Among the Pareto optimal solutions, a specific profile was identified that maximized the joint objective of quality and productivity. The profile can achieve high cell survival rate in a short freezing time, and thus could be useful in the actual process. In ongoing work, we are experimentally investigating the obtained profiles, and also assessing the impact of the choice of cryoprotective agent on the results.

Reference

1. Hayashi et al., Comput. Chem. Eng., 132, 106597 (2020)