The hanging-heart chip: A portable microfluidic device for high-throughput generation of contractile embryonic stem cell-derived cardiac spheroids.

Stem cell-derived cardiac spheroids are promising models for cardiac research and drug testing. However, generating contracting cardiac spheroids remains challenging because of the laborious experimental procedure. Here, we present a microfluidic hanging-heart chip (HH-chip) that uses a microchannel and flow-driven system to facilitate cell loading and culture medium replacement operations to reduce the laborious manual handling involved in the generation of a large quantity of cardiac spheroids. The effectiveness of the HH-chip was demonstrated by simultaneously forming 50 mouse embryonic stem cell-derived embryonic bodies, which sequentially differentiated into 90% beating cardiac spheroids within 15 days of culture on the chip. A comparison of our HH-chip method with traditional hanging-drop and low-attachment plate methods revealed that the HH-chip could generate higher contracting proportions of cardiac spheroids with higher expression of cardiac markers. Additionally, we verified that the contraction frequencies of the cardiac spheroids generated from the HH-chip were sensitive to cardiotoxic drugs. Overall, our results suggest that the microfluidic hanging drop chip-based approach is a high-throughput and highly efficient method for generating contracting mouse embryonic stem cell-derived cardiac spheroids for cardiac toxicity and drug testing applications.