Recent advances of stem cell-based therapies in clinical trials have raised the need for large-scale manufacturing platforms that can supply clinically relevant doses to meet an increasing demand. Promising results have been reported using stirred-tank bioreactors, where human Mesenchymal Stromal Cells (hMSCs) were cultured in suspension on microcarriers (MCs), although the formation of microcarrier-cell-aggregates might still limit mass transfer and determine a heterogeneous distribution of hMSCs. A variety of MCs, bioreactor-impeller configurations, and agitation conditions have been established in an attempt to overcome the trade-off of ensuring good suspension while keeping the stresses to a minimum. While understanding and controlling the fluid flow environment of bioreactors has been initially under-appreciated, it has recently gained in popularity in the mission of providing ideal culture environments across different scales. This review article aims to provide a comprehensive overview of how rigorous engineering characterisation studies improved the outcome of biological process development and scale-up efforts. Reconciling these two disciplines is crucial to propose tailored bioprocessing solutions that can provide improved growth environments across a range of scales for the allogeneic cell therapies of the future.
Keywords: Cell therapy process development; Impeller design; Mesenchymal stromal cell bioprocessing; Stirred-tank bioreactors.
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