110 - Manufacturing solutions for mesenchymal stromal/stem cell therapy expansion

Abstract

There is a growing need within the regenerative medicine industry for closed cell culture systems able to support scalable manufacture of adherent cell therapies. Single-use stirred tank bioreactor systems are such a platform, having been proven effective for large scale production of allogenic microcarrier-based cell therapies. However, optimization of the bioreactor culture process is essential to maximize cell yield while maintaining cell function. We will review a mesenchymal stem/stromal cell (MSC) case study using qualified media, serum alternatives, and bioreactor process control strategies to achieve increased growth. In this study, we present a method to determine optimal bioreactor process parameters, such as agitation set-point, pH set-point, and microcarrier concentration in the Mobius® 3L single-use bioreactor for MSC expansion on microcarriers. Specifically, we have utilized Zwietering's equation for suspension of solids in stirred tanks to determine a theoretical agitation operating range for microcarrier cultures, and Kolmogorov's theory of turbulent eddy lengths to define upper agitation limits. Results from this study suggest it is critical to balance minimizing shear and maximizing cell access to nutrients, DO, and cell-to-microcarrier attachment and transfer to achieve optimal MSC growth. Specifically this work indicates an agitation rate creating a slight gradient of microcarriers, produces higher growth compared to a more traditional homogenous distribution. Additionally, MSC culture performance was found to be negatively impacted by pH values outside the range of 7.4–7.6 tested in this study. Start to finish solutions for expansion, including high quality reagents and process control strategies, are key to enabling technologies for success in commercializing cell therapies.