Utilizing an automated hollow-fiber perfusion system for large-scale expansion of suspension cells

We established a novel immunohematology test system based on engineered murine cells, which express blood group antigens. To support its clinical use for pre-analytic depletion of therapeutic antibodies, which requires high cell amounts, large-scale expansion methods are needed. The Quantum^TM Cell Expansion System utilizes a hollow-fiber bioreactor for expansion of adherent and suspension cells. We explored the ability of Quantum to support reproducible large-scale expansion of our test cells.

The test cell used here is an immortalized cell line, the murine erythroleukemia cell line MEL, typically grown in flasks in high glucose DMEM with 20% FCS. For flask expansion cells are seeded at 2x10⁵ cells/ml and expanded to maximum concentrations of 2-3x10⁶ cells/ml. In the Quantum, cells are inoculated at a concentration of 3.2x10⁵ cells/ml and are fed constantly with culture media (DMEM, high glucose) containing 2% FCS through the intracapillary side at flow rates between 0.2 and 0.4 ml/min. For extracapillary medium culture media without FCS is used at maximum flow rates of 0.3 ml/min. Cell concentration and viability were tested, as well as the ability to absorb a defined amount of therapeutic antibodies from a spiked plasma.

Compared to expansion in T-flasks, with the Quantum we were able to generate 10 to 15-times higher cell concentrations peaking at 3-4x10⁷ cells/ml only using a tenth of FCS on a per-cell basis, resulting in a total cell number of 2-4x10⁹ cells per harvest every 3 to 4 days. The process is robust and delivers the targeted cell quantity with better predictability than flask-grown cells with equally consistent performance. Protocols for recirculation of media in the early stages of cell growth reduced the overall consumption of media. Targeting strategies for multiple harvests, we were able to better harvest definite numbers of cells from the bioreactor, lowering hands-on time for the system as well as improving cost efficiency of our cells.

With carefully titrated media compositions and adapted flow rates, Quantum allows expansion of suspension cells to very high concentrations and total yields compared to flask-based expansion, providing high viability and maintaining the phenotype of the cells. While in the work presented here, we only generated cells for diagnostic purposes, we posit that Quantum can be a useful technology for cell therapy laboratories where therapeutic cells can be expanded under ideal nutrient conditions.

Co-Autorin Dr. Maria Knaub ist Angestellte der Firma Terumo Blood and Cell Technologies. Des Weiteren bestehen keine Interessenskonflikte.