Elastomer-Grafted iPSC-Derived Micro Heart Muscles to Investigate Effects of Mechanical Loading on Physiology

Mechanical loading plays a critical role in cardiac pathophysiology. Engineered heart tissues derived from human induced pluripotent stem cells (iPSCs) allow rigorous investigations of the molecular and pathophysiological consequences of mechanical cues. However, many engineered heart muscle models have complex fabrication processes and require large cell numbers, making it difficult to use them together with iPSC-derived cardiomyocytes to study the influence of mechanical loading on pharmacology and genotype-phenotype relationships. To address this challenge, simple and scalable iPSC-derived micro-heartmuscle arrays (mu HM) have been developed. Dog-bone-shaped molds define the boundary conditions for tissue formation. Here, we extend the mu HM model by forming these tissues on elastomeric substrates with stiffnesses spanning from 5 to 30 kPa. Tissue assembly was achieved by covalently grafting fibronectin to the substrate. Compared to mu HM formed on plastic, elastomer-grafted mu HM exhibited a similar gross morphology, sarcomere assembly, and tissue alignment. When these tissues were formed on substrates with different elasticity, we observed marked shifts in contractility. Increased contractility was correlated with increases in calcium flux and a slight increase in cell size. This afterload-enhanced mu HM system enables mechanical control of mu HM and real-time tissue traction force microscopy for cardiac physiology measurements, providing a dynamic tool for studying pathophysiology and pharmacology.

Automated summary

Mechanical loading is crucial in cardiac pathophysiology, and engineered heart tissues from human iPSCs provide a platform to study the effects of mechanical cues. The development of iPSC-derived micro-heartmuscle arrays (mu HM) offers a simple and scalable system, allowing for observation of contractility shifts on substrates with varying elasticities.