Although suspension-based, scalable production of cardiomyocytes (CMs) has typically employed self-aggregated embryoid bodies (EBs), encapsulation of human induced pluripotent stem cells (hiPSCs) in biomimetic hydrogels provides tighter control over the cellular microenvironment. Employing a microfluidic system to rapidly encapsulate hiPSCs within PEG-fibrinogen microspheres (MS), here we compared the MS differentiation and resulting cardiac tissue function to suspension-differentiated EBs. MS were more consistent in size and shape both initially and over time and within and between batches. Resulting MS had an initial diameter of 673±22 µm (coefficient of variance, CV=0.03) and axial ratio of 1.03±0.01 (CV=0.01), while EBs had an initial diameter of 145±34 µm (CV=0.24) and axial ratio of 1.15±0.04 (CV=0.03). MS had a significantly higher number of CMs (2.8±1.8 versus 0.6±0.12) at day 10 per initial hiPSC and higher CM yield (75±14% CMs versus 56±16 %) compared to EBs based flow cytometry data (cTnT+, MF20+, n≥5, p&lt;0.05). Myocardial contractility was also enhanced in MS compared to EBs (similar CM content, day 10); maximum contraction velocity was 4x higher for MS than EBs (138.85±17.57 versus 33.4±5.1 µm/s) and maximum relaxation velocity was 14x higher (97±7.2 versus 7.42±0.44 µm/s). In conclusion, the microsphere-encapsulated hiPSCs differentiated into contracting cardiac tissues, with higher CM content and faster contractility than similarly differentiated EBs, demonstrating the potential of encapsulation to enhance the consistency, yield, and functionality of cardiac tissue produced in scalable culture systems.

Biomaterial scaffold supports stem cell differentiation for scaling up production of engineered cardiac tissue with improved functionality

ACS Fall 2021

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