Abstract 10701: Suspension Differentiation of Cardiomyocyte Spheroids Improves Quality and Yields

Abstract

Introduction: Improvements in stem cell viability, differentiation efficiency, and functional activity opened the door for advanced research applications in cardiac regeneration. However, the use of cell-based cardiac therapies, including implantable patches and cell products as well as in-vitro models for mechanistic studies and drug development requires large numbers of high-quality cardiomyocytes (CMs). Typically, differentiation is conducted in 6-well culture plates via the GiWi method, which uses small-molecule inhibitors of glycogen synthase kinase (GSK) and tankyrase to first activate and then suppress Wnt signaling. This monolayer method requires significant manual labor and cannot be easily scaled. Suspension culture and differentiation of free-floating hiPSC aggregates following similar biochemical cues offers advantages for commercial biomanufacturing purposes and provides a more physiological environment for cell development. Hypothesis: We assessed the hypothesis that when hiPSCs are cultured and differentiated in suspension they will produce CMs with improved yield, purity, and quality. Methods: hiPSCs were expanded as aggregates in culture flask using a fed-batch approach then differentiated over a 12 day period with Wnt activation on day 0 and inhibition on day 3. Optimization studies examined purity on day 9 and complete characterization via morphological assessments and CM-specific genes expression was done on day 12 following metabolic purification. All studies were conducted with a minimum of 4 replicates. Results: Optimal conditions for both purity and yield based on cardiac troponin T staining were achieved with an initial cell density of 1.6x10 6 cells/mL, 6 μM CHIR99021, and 55 rpm shaking. After scaling to 30mL culture volume the purity of hiPSC-CMs differentiated via our novel protocol was 98.2±0.8% with yields of 1.47±0.18 million cells/mL and less between-batch purity variability than hiPSC-CMs produced in 2D cultures. Conclusions: Suspension differentiation of hiPSCs into CMs in a widely available format results in improved biomanufacturing endpoints. Therefore, this method functions as a groundwork for future bioreactor systems to produce the large number of cells needed for clinical applications.