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

The impact of repeated temperature cycling on cryopreserved human iPSC viability stems from cytochrome redox state changes

Human induced pluripotent stem cells (hiPSCs) are an attractive cell source for regenerative medicine. For its widespread use as a starting material, a robust storage and distribution system in the frozen state is necessary. For this system, managing transient warming during storage and transport is essential, but how transient warming affects cells and the mechanisms involved are not yet fully understood. This study examined the influence of temperature cyclings (from -80°C to -150°C) on cryopreserved hiPSCs using a custom-made cryo Raman microscope, flow cytometry, and performance indices to assess viability. Raman spectroscopy indicated the disappearance of mitochondrial cytochrome signals after thawing. A reduction in the mitochondrial membrane potential was detected using flow cytometry. The performance indices indicated a decrease in attachment efficiency with an increase in the number of temperature cycles. This decrease was observed in the temperature cycle range above the glass transition temperature of the cryoprotectant. Raman observations captured an increase in the signal intensity of intracellular dimethyl sulfoxide (DMSO) during temperature cycles. Based on these results, we proposed a schematic illustration for cellular responses to temperature fluctuations, suggesting that temperature fluctuations above the glass-transition temperature trigger the movement of DMSO, leading to cytochrome c oxidation, mitochondrial damage, and caspase-mediated cell death. This enhances our understanding of the key events during cryopreservation and informs the development of quality control strategies for hiPSC storage and transport.

Approach of resource expenditure estimation toward mechanization in the manufacturing of cell-based products

Recent developments for the manufacturing of cell-based products have focused on the advancement of products to clinical trials or commercialization, with awareness of the importance of cost-based effectiveness in cell manufacturing. The mechanization of cell-processing operations is advantageous for the reproducibility and stability of product quality and is thought to reduce the cost-of-goods through the life cycle of the product in a scale-up system; however, few cases of the implementation exist. This study developed an estimation method for the resource expenditure of cell-processing operations in the manufacturing of cell-based products. To estimate resource expenditures, we evaluated the manufacturing processes by operations involving entering into the surrounding area of cell processing zone, materials loading, cell-processing operation, cleaning, and leaving from the surrounding area. The cell-processing operation is applicable to manual or robotic cell manufacturing system in a biosafety cabinet or an isolator system. In cases of low annual batch numbers of manufacturing (batch number <33), the resource expenditure of cell-processing operations in a robotic operation system installed in the isolator system is estimated to be higher compared with a manual operation system in the isolator system due to additional initial costs for design and fabrication of the robotic operation system containing robot arms. With increasing numbers of annual batches, the resource expenditure decreases for robotic operating system, leading to an advantageous juncture where the resource expenditure of a robotic operation system is equivalent to that of a manually operated system, whereby the labor cost for cell-processing operations rises. In addition, the expertise of operations required for cell manufacturing is suggested to foster potential risks associated with the operation skills or turnover of operators, and the cost of education and training increases due to the necessity of persistent human resource development. Collectively, revealing the approach for installation of robotic operation system in cell manufacturing.

Apoptosis-based method for determining lot sizes in the filling of human-induced pluripotent stem cells

Standardization in process design and operation is needed in the commercial production of human-induced pluripotent stem (hiPS) cells. Lot sizing in the filling of hiPS cells into containers, a part of the preservation process, also needs to be standardized because of the temporal changes in cell quality during the process. Here, we present an apoptosis-based method that can determine lot sizes in the filling of hiPS cells considering temporal changes in cell quality. Two indicators were developed for (i) the cell quality change using reactive oxygen species (ROS) measurement and (ii) the cell survival and probability of filling success, which are parts of the lot-sizing problem. Using computational simulation, a map out of the optimal lot size was produced that minimized the expected production costs at a given cell demand and an acceptable change in cell quality. At a filling temperature of 4°C, the largest possible lot size was calculated as 6 L (corresponding to a filling time of 125 min). The results of a sensitivity analysis recommended cold filling or the addition of an antioxidant. The presented method is effective to determine the lot size considering the change in cell quality during filling. The study uniquely combines the experimental results with mathematical modeling and computational simulation techniques. The map out of the optimal lot size could guide the development of industrial filling processes of hiPS cells.

A distribution-based approach for determining lot sizes in the filling of human-induced pluripotent stem cells

Introduction

Toward the commercial production of human-induced pluripotent stem (hiPS) cells, the process design and operation have to be standardized. Considering the change in cell quality during filling of the hiPS cells into containers, lot sizing during filling also needs to be standardized.

Methods

We present a distribution-based approach that can be used for determining the lot sizes in the filling of hiPS cells by considering change in cell quality during filling. The approach describes the “survival capability” of the cells as a continuous probability distribution, and expresses the change in quality during filling by “trimming” the distribution.

Results

A lognormal distribution was assumed as the survival capability distribution of the cells that were to be filled. The distributions after different filling times were calculated, which were compared with the distribution of the initial filling time regarding the yield of the cells and the similarity. These conditions served as strong quality constraints in determining an economically optimal lot size.

Conclusions

The presented conceptual approach would be effective in determining the lot size considering the change in cell quality during filling. For actual application, measuring the distribution information on the survival capability of hiPS cells is encouraged.

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A novel lot sizing approach was developed for filling hiPS cells.

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Survival capability of hiPS cells was assumed to follow a lognormal distribution.

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The distributions of survival capability were calculated to determine the lot size.

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Monte Carlo simulation was useful in comparing distributions.

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A case study demonstrated the effectiveness of the approach.

Variation in the manufacturing reproducibility of autologous cell-based products depending on raw material shipment conditions

To prepare an autologous cell-based product in a cell processing facility, the raw material, which is collected from a patient, must first be shipped from a medical institution to the facility. The quality of this raw material varies depending on the patient, and variations due to transport methods also occur. Because the quality must be uniform and manufacturing processes need to be adjusted to account for these variations, determining the effect of shipment conditions on raw materials is very important for estimating cell manufacturability in the process design. In this study, a group of medical institutions located in different areas requested similar cell-based products processed by the same manufacturing method to a company that is licensed under the Act on the Safety of Regenerative Medicine in Japan. Manufacturing reproducibility was analyzed based on 456 cell batches received from two clinics that were processed used the same manufacturing method. The specific growth rates that were observed in the early growth phase supposed that the proliferative potential of the primary cells in the raw material was influenced by transit time. Simultaneously, the variation of the specific growth rates in the late phase were supposed to be hardly occurred. Thus, this study evaluated shipping conditions of the raw materials for an autologous cell-based product, and a strategy for verifying the influence of transportation on quality in manufacturing was suggested.