Stirred Suspension Culture for Scalable Production and Differentiation of Human Pluripotent Stem Cells

The success of human pluripotent stem cells (hPSCs) as a source of future cell therapies hinges in part on the availability of a robust scalable culture system that can readily produce clinically relevant number of cells and their derivatives. Stirred suspension culture has been identified as one of such promising platforms due to its ease of use, scalability, and widespread use in the pharmaceutical industry (e.g., CHO cell-based production of therapeutic proteins) among others. However, culture of undifferentiated hPSCs in stirred suspension is a relatively new development in the past several years, and little is known beyond empirically optimized culture parameters. The goal of this study was to elucidate the impact of fluidic agitation on hPSCs in stirred suspension culture. In particular, we systematically investigated various agitation rates to characterize their impact on cell yield, viability, and maintenance of pluripotency. Additionally, we closely examined the distribution of cell aggregates and how the observed culture outcomes are attributed to their size distribution. Our results showed that moderate agitation maximized the propagation of hPSCs by controlling the cell aggregates below the critical size, beyond which the cells suffer from diffusion limitation, while limiting cell death caused by excessive fluidic forces. Furthermore, we observed that fluidic agitation could regulate not only cell aggregation, but also expression of some key signaling proteins in hPSCs. Upon discovering this mechanosensitive effector enabled a novel approach for linking expansion and cardiac differentiation to generate over 90% cardiomyocytes. In addition, these cardiomyocytes displayed highly organized sarcomere structure which suggests an improved maturation in their morphology. Altogether, results presented in this study indicate the new possibility of guiding stem cell fate determination by fluidic agitation in stirred suspension cultures