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For β-cell replacement therapies, one challenge is the manufacturing of enough β-cells (Edmonton protocol for islet transplantation requires 0.5–1 × 106 islet equivalents). To maintain their functionality, β-cells should be manufactured as 3D constructs, known as spheroids. In this study, we investigated whether β-cell spheroid manufacturing can be addressed by a stirred-tank bioreactor (STR) process. STRs are fully controlled bioreactor systems, which allow the establishment of robust, larger-scale manufacturing processes. Using the INS-1 β-cell line as a model for process development, we investigated the dynamic agglomeration of β-cells to determine minimal seeding densities, spheroid strength, and the influence of turbulent shear stress. We established a correlation to exploit shear forces within the turbulent flow regime, in order to generate spheroids of a defined size, and to predict the spheroid size in an STR by using the determined spheroid strength. Finally, we transferred the dynamic agglomeration process from shaking flasks to a fully controlled and monitored STR, and tested the influence of three different stirrer types on spheroid formation. We achieved the shear stress-guided production of up to 22 × 106 ± 2 × 106 viable and functional β-cell spheroids per liter of culture medium, which is sufficient for β-cell therapy applications. [ABSTRACT FROM AUTHOR]

Human mesenchymal stem cells (hMSCs) are manufactured as cell therapy products. This requires a tightly controlled and fully understood production process, usually taking place in a stirred‐tank bioreactor. In this review, the impact of bioreactor geometry as well as equipment‐related parameters is discussed. We provide a theoretical background for the engineering of hMSC spheroids with a defined size and evaluate the process parameters needed for the microcarrier‐based expansion of hMSCs. Finally, and based on experimental data, ideal bioreactor setups for each type of process are recommended. [ABSTRACT FROM AUTHOR]